Papers - Sawada, Tatsuo

Dynamic pressure change of a liquid sloshing in a rotating, laterally oscillating, cylindrical container

Tatsuo Sawada, Eisaku Yokose and Yusuke Saito

CD-Proceedings of 2018 Sustainable Industrial Processing Summit and Exhibition 4   101-108 2019.06

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  2291-1227

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We investigated characteristics of water sloshing in a rotating, laterally oscillating, cylindrical container both theoretically and experimentally. In our experiment, the time-dependent dynamic pressure of the water on the wall rather than the free-surface displacement of the water was measured, and the experimental parameters are the lateral forcing frequency, the rotation frequency of the cylindrical container, and the water depth. We also conducted a theoretical analysis to understand the experimental results. The swirling of water in the container had some frequency components; the frequency responses of each frequency component are examined herein.

Application of knockdown pontoons of the emergency measures for volcanic hazards of Mount Fuji

Yuji Doya, Tatsuo Sawada, Taisuke Morikawa, Yuya Iseda

Journal of Fujiology (Japan Society of Fujiology)  15 ( 2 ) 1 - 15 2019.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2433-0310

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We investigate the stability and strength of a reinforced, rectangular-hull knockdown pontoon to determine the feasibility of the usage of knockdown pontoons for emergency procedures in case of Mt. Fuji volcanic hazards. The stability of the self-propelled ship is evaluated by the metacentric height of the ship. However, a pontoon with a rectangular hull exhibits a large metacentric height that could cause the loss of ship stability. We propose a new technique to avoid an overly optimistic evaluation of a pontoon’s stability. The hull strength evaluation method that is used in case of the reinforced knockdown pontoon differentiates between two types of load distributions, divided load and concentrated load. By comparing the evaluations that were obtained using these two types of load distribution, we clarified the differences between these approaches.


Magnetic fluid flow under DC and AC magnetic fields

Yuta Itahashi, Ryutaro Hirano and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  59 ( 1 ) 341 - 347 2019.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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This study reports magnetic fluid flow in a square duct under DC, AC, and DC+AC magnetic fields. We measured pressure drop with applying different magnetic fields. Under magnetic fields, flow resistance increased by forming a cluster so that pressure drop and friction factor also increased. From FFT analysis of the pressure drop, we obtained different power spectrum for AC and DC+AC magnetic fields.

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Change of ultrasonic propagation velocity in MR fluid under AC magnetic fields

Takashi Fukumoto, Yuya Tanaka and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  59 ( 1 ) 335 - 340 2019.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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This paper reports the experimental studies on a magneto-rheological (MR) fluid under AC magnetic fields. Magnetic clusters in the MR fluid are formed along the magnetic fields. The ultrasonic propagation velocity changes owing to the presence of clustering structures in the MR fluid. We investigated clustering structures by measuring this change in the ultrasonic propagation velocity. The results indicate that magnetic clusters in the MR fluid depend on the elapsed time, intensity, frequency, and angle of the AC magnetic fields.

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Frequency response of a liquid sloshing in a rotating, laterally oscillating, cylindrical vessel

Eisaku Yokose, Yusuke Saito and Tatsuo Sawada

MATEC Web of Conferences (EDP Sciences)  211   15003(6pp) 2018.10

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  2261-236X

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We have investigated the free-surface fluctuations of liquid in a rotating, laterally oscillating, cylindrical vessel. We measured the time-dependent fluid-dynamic pressure instead of the free surface luctuations. From an FFT analysis of the dynamic pressure, we obtained two significant frequencies. They are associated, respectively, with waves that rotate in the same direction, and in the opposite direction, relative to the rotation of the vessel. We also examined these results using linearized wave theory.

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Dynamic pressure change in a rotating, laterally oscillating cylindrical container

Yusuke Saito and Tatsuo Sawada

Journal of Ocean Engineering and Science (Elsevier)  3 ( 2 ) 91 - 95 2018.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2468-0133

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We examined wave phenomena pertinent to water in a rotating, laterally oscillating cylindrical container. In particular, we measured the time-dependent dynamic water pressure and pressure change by fast Fourier transform analysis. The swirling of water in the container had three frequency components; the frequency responses of each frequency component are reported herein. When swirling occurs in a rotating cylindrical container, it was found that the wave rotating in the same direction as the rotation of the cylindrical container and the wave rotating in the opposite direction to the cylindrical container exist at the same time.

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Changes in the resistance force of a magneto-rheological shock absorber induced by a magnetic field

Tatsuo Sawada, Takuma Endo, Yuzo Shimizu and Hitoshi Nishida

Materials Science Forum (Trans Tech Publications, Switzerland)  915   39-44 - 44 2018.03

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1162-9752

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The magnetic particles in an MR fluid form clusters parallel to the direction of the applied magnetic field, and yield stress is generated. As a result, the apparent viscosity of the MR fluid increases. In the present paper, we propose a theoretical approach for obtaining the resistance force controlled by the magnetic field using an MR flow model. We use a mechanical model of an MR fluid pipe flow with a tapered pin. Moreover, we conduct some experiments to test our theoretical approach.

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Liquid sloshing in a rotating, laterally oscillating cylindrical container

Yusuke Saito and Tatsuo Sawada

Universal Journal of Mechanical Engineering (Horizon Research Publishing)  5 ( 3 ) 97 - 101 2017.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2332-3361

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Free surface movement of water in a rotating, laterally oscillating cylindrical container was qualitatively investigated. The swirling direction was determined by forcing the frequency and rotating direction of the cylindrical container. The swirling direction was opposite to that of the rotating cylindrical container when the forcing frequency was low, whereas the crest of the free surface swirled in the same direction as that of the rotating cylindrical container when the forcing frequency greatly increased. Unstable swirling occurred when swirling direction changes, but it disappeared as the rotating frequency increased.

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Suppression of heat transfer of turbulent magnetic fluid flow by applying uniform magnetic field

Masaaki Motozawa, Kosuke Takeda, Yasuo Kawaguchi, Tatsuo Sawada and Mitsuhiro Fukuta

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  52 ( 1-2 ) 113 - 120 2016.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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Forced convective heat transfer of turbulent magnetic fluid flow is remarkably suppressed by applying magnetic field. Detailed investigation of this suppression of turbulent heat transfer of magnetic fluid was carried out experimentally in this study. The result shows that the suppression of heat transfer becomes strong by applying stronger magnetic field, but is saturated at a certain strength of magnetic field. This suppression depends on not only magnetic field intensity but also flow condition. For generalization of the suppressed heat transfer characteristics of turbulent magnetic fluid flow by applying magnetic field, we proposed Mh number which is defined by Re divided by a root of magnetic field intensity normalized by saturated magnetization of magnetic fluid. It is found that suppressed heat transfer of magnetic fluid almost linearly increases with increasing Mh number.

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Effect of a tapered metering pin on magnetorheological fluid under an impact load

Yuzo Shimizu, Takuma Endo, Shintaro Takagi and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  52 ( 3-4 ) 1393 - 1400 2016.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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We proposed a mechanical model of MR fluid pipe flow and compared with the experiment results of the flow under an impact load, and conducted drop impact tests with four types of tapered metering pins and qualitative analysis of effects of the pins. The results show that the shape of the pins has some effect on the entire shock absorption process whereas magnetic field strength affects the post-peak behavior only, and shock absorption with a longer tapered pin is more widely controllable by magnetic field.

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Effect of tapered metering pin on magnetorheological fluid subjected to shock loading

Yuzo Shimizu, Shintaro Takagi and Tatsuo Sawada

Materials Science Forum (Trans Tech Publications, Switzerland)  856   3 - 8 2016.05

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  0255-5476

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Using four types of tapered metering pins, we conducted drop impact tests and a qualitative analysis of effects of the pins on MR fluid with a magnetic field applied around an orifice area. The tapered metering pins changed the piston stroke. The results indicate that the shape of the pins has some effect on the overall shock absorption process whereas magnetic field strength affects the post-peak behavior only. These results show that a tapered metering pin has applicability to shock absorbers using an MR fluid.

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Vibrating properties of magnetic fluid tuned liquid column damper with different U-pipes

Shinya Kondo, Kazuki Ikari and Tatsuo Sawada

Materials Science Forum (Trans Tech Publications, Switzerland)  856   21 - 25 2016.05

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  0255-5476

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We performed vibration experiments for three types of U-pipes, and obtained the following results: (1) The shape of the bottom and elbow of the U-pipe has no influence on the natural frequency change of an MF-TLCD (Magnetic-Fluid Tuned Liquid Column Damper) when a magnetic field is applied. (2) When using a U-pipe with an elbow with a larger curvature, it is possible to reduce the damping force on the liquid column and improve MF-TLCD performance.

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Effect of magnetic field direction on forced convective heat transfer of magnetic fluid

Masaaki Motozawa，Kyohei Kino, Tatsuo Sawada，Yasuo Kawaguchi, Mitsuhiro Fukuta

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  23 ( 3 ) 612 - 617 2015.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

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We investigated the forced convective heat transfer of magnetic fluid by applying magnetic field in a vertical, a parallel and an axial direction against heat transfer direction by using a rectangular duct. In the case of laminar flow, heat transfer was enhanced in the vertical direction and slightly enhanced in the axial direction, but hardly changed in the parallel direction. In contrast, in the case of turbulent flow, heat transfer was suppressed in all directions. The suppression level in vertical and parallel direction is similar, but the suppression in axial direction is much weaker than those in other directions.

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The effect to the damping performance of magnetic fluid tuned liquid column damper induced by various damping coefficient of liquid column

Kazuki Ikari, Shinya Kondo, Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  23 ( 2 ) 368 - 373 2015.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

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Magnetic fluid tuned liquid column damper (MF-TLCD) is a kind of semi-active damper that uses magnetic fluid as its working fluid. An MF-TLCD alters the natural frequency of the magnetic fluid column that forms the resident liquid inside the MF-TLCD by applying a magnetic field. We quantitatively investigated the damping coefficient generated by the flow of magnetic fluid, which is strongly related to the damping performance. Three kind of U-pipes that have each different shape were prepared and single-degree-of-freedom oscillation was performed with each those pipes. Finally, we discussed the effect to the damping performance of MF-TLCD induced by various damping coefficient subjected to magnetic field and configurations of those U-pipes.

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磁性流体同調液柱管ダンパーの容器形状が液柱振動に及ぼす影響

近藤真也, 碇 一暉, 澤田達男

2014 JSMFR selected proceedings (磁性流体研究連絡会)     28 - 30 2015.01

Research paper (conference, symposium, etc.), Joint Work

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磁性流体同調液柱管ダンパーはU字管内の磁性流体液柱を付加振動系とする制振装置で、磁場印加によって液柱固有振動数の制御が可能である。本研究では異なる三つの形状のU字管容器で加振実験を行い、それぞれの比較検討を行った。2014年12月の磁性流体連合講演会で発表された論文が，査読されて本論文集に掲載された。

Damping characteristics of a magnetic fluid tuned liquid column damper under static magnetic fields

Toshiyuki Oyamada, Hideaki Masuda, Kazuki Ikari and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  45 ( 1-4 ) 659 - 665 2014.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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Magnetic fluid TLCD (MF-TLCD) is a novel type of semi-active damper in which the natural frequency can be controlled by applying magnetic field. We tuned the natural frequency of a column of magnetic fluid to excitation frequency, and demonstrated that the damping performance can improved compared with the case without magnetic field.

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Effect of chamfered orifice inlet on magnetorheological fluid subjected to shock loading

Ahmad Isnikurniawan, Hiromichi Ohba, Hiro Kaneko, Ryo Yoshizawa and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  45 ( 1-4 ) 683 - 688 2014.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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This paper presents an investigation on the effect of chamfered orifice inlet on magnetorheological (MR) fluid subjected to shock loading. Two different orifices (no chamfer and chamfered at 60 degrees angle on the inlet area) are used. The MR fluid is subjected to a shock loading, and the magnetic field is applied on the orifice area. Experiments have been conducted by measuring piston displacement, impact force and pressure difference between the inlet and outlet of the orifice. Based on the experiment result, the effect of chamfered orifice inlet on MR fluid subjected to shock loading is discussed.

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Two-Layer sloshing of magnetic fluid and silicone oil under horizontal magnetic field

Takayoshi Ishiyama, Shunsuke Kaneko, Shin-Ichiro Takemoto and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  45 ( 1-4 ) 675 - 682 2014.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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We carried out experiments on two-layer sloshing using a magnetic fluid and silicon oil, and measured displacements of free surface and interface by a laser sensor. We also carried out theoretical investigation using a linear short-wave theory. We compared with experimental and theoretical results.

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Ultrasonic propagation characteristics of a magnetic fluid under AC magnetic fields

Yasuhiro Fujita, Ahmad Isnikurniawan, Sachio Tanimoto and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  45 ( 1-4 ) 667 - 673 2014.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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We conducted experimental studies as the ultrasonic propagation characteristics of a magnetic fluid (MF) under AC magnetic fields. The change rate of sound velocities were related to the formation of clusters in MF and it decreased with increase of AC frequencies.

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Relation between the dynamic pressure and displacement of the free surface in two-layer sloshing with magnetic fluids and silicone oil

Takayoshi Ishiyama, Shunsuke Kaneko, Shin-ichiro Takemoto and Tatsuo Sawada

Materials Science Forum (Trans Tech Publications, Switzerland)  792   33 - 38 2014.08

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1662-9752

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We carried out experiments of two-layer sloshing using magnetic fluids and silicone oil, and measured dynamic pressure change by using pressure transducers. We also investigated displacements of free surface. We compared the dynamic pressure with displacements of the free surface and clarified the correlation between them.

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Frequency analysis of semi-active tuned magnetic fluid column damper with two electromagnets

Kazuki Ikari, Hideaki Masuda, Toshiyuki Oyamada and Tatsuo Sawada

Materials Science Forum (Trans Tech Publications, Switzerland)  792   275-280 2014.08

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1662-9752

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We designed a new semi-active Tuned Liquid Column Damper (TLCD) which uses Magnetic Fluid as its working fluid (MF-TLCD). We investigated the damping characteristics of MF-TLCD which has the two electromagnets, and considered transition of the natural frequency that is strongly related to the damping performance. We presented the momentum equation of MF-TLCD, and solved it numerically. Numerical results were compared with experimental results.

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Investigation of inner structure in magnetic fluid under compression using ultrasonic measurement

Ahmad Isnikurniawan, Yasuhiro Fujita, Sachio Tanimoto and Tatsuo Sawada

Materials Science Forum (Trans Tech Publications, Switzerland)  792   147-152 2014.08

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1662-9752

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Ultrasonic propagation velocity in a magnetic fluid under compression was investigated. Ultrasonic propagation velocity in a magnetic fluid changed with the magnetic flux density and the compressive force. This change is related with cluster formation in a magnetic fluid. Experiment results indicated that cluster formation in a magnetic fluid seemed strongly affected by compressive force.

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Characteristics of ultrasonic propagation in a magnetic functional fluid under AC magnetic fields

Yasuhiro Fujita, Ahmad Isnikurniawan, Sachio Tanimoto, Kanta Moriyama, Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  22 ( 2 ) 280 - 285 2014.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

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This paper reports experimental studies about anisotropy and attenuation as characteristics of ultrasonic propagation in a magnetorheological fluid (MRF) under AC magnetic fields. Parameters of this studies are magnitude of AC magnetic fields, frequencies of AC magnetic fields and angles between directions of ultrasonic propagation and magnetic field. As results of change rate of sound velocity, MRF has characteristics of time dependence, frequencies dependence and anisotropy under AC magnetic fields. Also, length of clusters in MRF became short with increase of frequencies of AC magnetic fields. Attenuation decreased with increase of the angles between directions of ultrasonic propagation and magnetic field. But, attenuation did not change with increase of frequencies of AC magnetic fields.

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Damping characteristics of semi-active tuned liquid column damper with a magnetic field

Toshiyuki Oyamada, Hideaki Masuda, Kazuki Ikari and Tatsuo Sawada

Magnetohydrodynamics (Institute of Physics, University of Latvia)  49 ( 3-4 ) 516 - 519 2013.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0024-998X

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We designed a novel semi-active TLCD (Tuned Liquid Column Damper) that uses a magnetic fluid (MF) as a working fluid. Two electromagnets were used and a magnetic field was applied symmetrically to both sides of the magnetic fluid column. The frequency response of the MF-TLCD apparatus was measured, and the influence of magnetic fields on the natural frequency of the magnetic fluid column was investigated.

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Effect of a magnetic field on sloshing in a two-layer fluid

Shunsuke Kaneko, Takayoshi Ishiyama, Shin-ichiro Takemoto and Tatsuo Sawada

Magnetohydrodynamics (Institute of Physics, University of Latvia)  49 ( 3-4 ) 520-524 2013.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0024-998X

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Sloshing of a two-layer fluid with a water based magnetic fluid and a silicone oil was investigated. A magnetic field was applied by two permanent magnets, and these were placed near the interface between a magnetic fluid and a silicone oil. Several frequency response spectrum were received in each experimental conditions. Changes in the sloshing behaviour of the two-layer fluid with several magnetic fields were reported.

Ultrasonic characteristics of a magnetic fluid under compressive force

Yasuhiro Fujita, Ahmad Isnikurniawan, Sachio Tanimoto and Tatsuo Sawada

Magnetohydrodynamics (Institute of Physics, University of Latvia)  49 ( 3-4 ) 368-371 2013.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0024-998X

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The characteristics of the inner structure of a magnetic fluid (MF) under high pressure were investigated experimentally. The ultrasonic propagation velocity was changed with the application of magnetic fields and pressure. The change was related to cluster formation in the MF fluid. Based on the experimental results, the effect of pressure on the inner structure in MF was analyzed.

Investigation of ultrasonic properties of MR fluid under various sweep rates of magnetic field

Ahmad Isnikurniawan, Yashuhiro Fujita, Sachio Tanimoto and Tatsuo Sawada

Magnetohydrodynamics (Institute of Physics, University of Latvia)  49 ( 3-4 ) 430-433 2013.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0024-998X

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The ultrasonic propagation velocity of MR fluid under various magnetic field sweep rates was measured. A magnetic flux density was applied from 0 to 400 mT over different lengths of time. On the basis of the experimental results, the effect of the magnetic field sweep rates on the cluster formation of MR fluid was analyzed.

Vibration Analysis of the Tuned Liquid Column Damper with a Magnetic Fluid

Hideaki Masuda, Toshiyuki Oyamada, Kazuki IKari and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  21 ( 2 ) 228-233 2013.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

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We present the equation of motion of a MF-TLCD (Tuned Liquid Column Damper with a Magnetic Fluid), and solved it numerically using a 4th-order Runge-Kutta method. Using the numerical results, we demonstrate the frequency responses of a MF-TLCD and the effect of the magnetic field on the natural frequency of a MF-TLCD. We also compare numerical results with experimental results, and show that they are coincident qualitatively.

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Variation of forced convective heat transfer in rectangular duct flow of a magnetic fluid under magnetic field

Masaaki Motozawa, Tsukasa Sekine, Tatsuo Sawada and Yasuo Kawaguchi

Journal of Physics: Conference Series (IOP Publishing)  412   012025(11pp) 2013.02

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1742-6588

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Variation of forced convective heat transfer in a rectangular duct flow of a magnetic fluid under a magnetic field was investigated experimentally. The results of the experiments show that in the case of laminar flow of the magnetic fluid, when a magnetic field is applied to a magnetic fluid flow, heat transfer locally increases in the region where the magnetic field exists. In contrast, in the turbulent flow of the magnetic fluid, heat transfer is not enhanced but reduced. In order to better understand this heat transfer phenomenon, we measured the velocity distribution of magnetic fluid flow by the Ultrasonic Velocity Profile (UVP) method. In the case of laminar flow, the result shows that the flow velocity at the center of the rectangular duct decreases and the velocity gradient in the near-wall region increases. Moreover, we calculated the flow resistance under a magnetic field by measurement of the pressure gradient, and the relationship between heat transfer and flow resistance was discussed.

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Effect of an applied magnetic field on sloshing pressure in a magnetic fluid

Shunsuke Kaneko, Takayoshi Ishiyama and Tatsuo Sawada

Journal of Physics: Conference Series (IOP Publishing)  412   012018(7pp) 2013.02

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1742-6588

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Dynamic pressure response in an oscillating rectangular container filled with a magnetic fluid under a horizontal magnetic field was discussed. An investigation was made experimental approach based on the measurement of pressure at several points by pressure transducers and the real-time computation of a discrete Fourier transform.

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Experimental study on damping characteristics of the tuned liquid column damper with magnetic fluid

Hideaki Masuda, Toshiyuki Oyamada and Tatsuo Sawada

Journal of Physics: Conference Series (IOP Publishing)  412   1-9(012049) 2013.02

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1742-6588

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We designed a novel semi-active damper using a magnetic fluid as a working fluid of the tuned liquid column damper (MF-TLCD). Experiments were performed to analyze the effect of a magnetic field on natural frequencies of the MF-TLCD. Based on the experimental results, relations among setting positions of an electromagnet, strength of magnetic field, and changes of a natural frequency were discussed.

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Investigation of cluster growth in MR fluids using ultrasonic wave propagation

Ahmad Isnikurniawan, Jun Kuroiwa, Shunnosuke Abell and Tatsuo Sawada

Journal of Physics: Conference Series (IOP Publishing)  412   012019(5pp) 2013.02

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1742-6588

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We carried out experiments by applying different magnetic field (M/F) sweep rates to MR fluid. The ultrasonic propagation velocity was measured and the change of ultrasonic propagation velocity was calculated for various M/F sweep rate. The relation between the change of ultrasonic propagation velocity and M/F sweep rate was discussed.

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Application of ultrasonic technique for magnetic functional fluids

Tatsuo Sawada, Ahmad Isnikurniawan, Masaaki Motozawa, Muhammad Agung Bramantya

Final Report of Research Committee on Integration of Fluid Power Systems with Functional Fluids (The Japan Fluid Power System Society)     65-69 2012.09

Research paper (conference, symposium, etc.), Joint Work

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日本フルードパワーシステム学会の「機能性流体を核としたフルードパワーシステムの融合化に関する研究委員会」研究成果報告書を分担執筆した。

Experimental investigation on heat transfer characteristics in rectangular duct flow of a magnetic fluid under magnetic field

Masaaki Motozawa, Jia Chang, Tatsuo Sawada and Yasuo Kawaguchi

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  39 ( 1-4 ) 583-588 2012.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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Forced convective heat transfer characteristics in a rectangular duct flow of a magnetic fluid under a magnetic field were investigated experimentally. Experiments were performed in which the magnetic field intensity was changed from 0 mT to 500 mT. The Reynolds number based on the hydraulic diameter was set to 820 (laminar flow), 1630 and 2450 (turbulent flow). The magnetic fluid in the rectangular duct was heated with a uniform heat flux. The results of the experiments showed that in the case of laminar flow of the magnetic fluid, when the magnetic field is applied to the magnetic fluid flow, the heat transfer coefficient increases locally in the region where the magnetic field exists. In contrast, in the turbulent flow of the magnetic fluid, heat transfer is not enhanced, but slightly decreases.

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Cluster formation in two-dimensional channel flow of a magnetic fluid under uniform magnetic field

Akihiro Nakamura, Satoshi Suzuoka and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  39 ( 1-4 ) 563-568 2012.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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The two-dimensional channel flow of a magnetic fluid was experimentally investigated. When a magnetic field is applied to a magnetic fluid, ferromagnetic particles aggregate along the direction of the magnetic field and form clusters. The pressure drop of the magnetic fluid flow changes according to cluster formations. The effect of the applied magnetic field on the pressure drop was determined. The ultrasonic propagation velocity was also measured to clarify the effect of cluster formations.

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Effect of a uniform magnetic field on magnetorheological fluid under an impact load

Yoshitaka Moroka, Ahmad Isnikurniawan, Hiromichi Ohba and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  39 ( 1-4 ) 569-573 2012.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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We carried out an impact experiment in order to investigate the influence of magnetic field intensity and inner diameter of the orifice on MR fluid motion under an impact load. The experiment was conducted by measuring the piston displacement. From the piston displacement, its velocity and acceleration were calculated.

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Ultrasonic propagation attenuation in an MR fluid under an external magnetic field

Ahmad Isnikurniawan, Jun Kuroiwa, Shunnosuke Abell and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (Japan Society of Applied Electromagnetics and Mechanics)  20 ( 2 ) 434-439 2012.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

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Experiments were performed to measure how the ultrasonic propagation attenuation in an MR fluid under an external magnetic field was affected by temperature, elapsed time, magnetic field intensity, magnetic field angle, removal of the magnetic field, and hysteresis. The influence of the clustering structures on change of ultrasonic propagation attenuation in MR fluids is discussed.

Dynamic pressure change of a magnetic fluid in a lateral oscillating container

Shunsuke Kaneko, Jean Klingler, Takayoshi Ishiyama and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (Japan Society of Applied Electromagnetics and Mechanics)  20 ( 2 ) 416-421 2012.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

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Dynamic pressure change of a magnetic fluid in a lateral oscillating container was investigated. An experimental approach based on the measurement of pressure at several points by small disc-type pressure transducers was used. Several frequency response spectra are received. These results indicated that the free surface disturbance caused by the sloshing was suppressed by the applied magnetic field.

Experimental investigation into the effect of a magnetic field on magnetorheological fluids under an impact load

Ahmad Isnikurniawan, Yoshitaka Moroka, Hiromichi Ohba and Tatsuo Sawada

Materials Science Forum (Trans Tech Publications, Switzerland)  721   179-184 2012.06

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1662-9752

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We perform a qualitative analysis to investigate the effect of a magnetic field on MR fluids under an impact load. An experimental apparatus that consists of a drop-test tower was developed to simulate the impact load, and an MR fluid in a U-pipe was subjected to the impact load via a piston rod. We measured the displacement and velocity of the piston rod, and the influence of a given magnetic field on the behavior of MR fluids under an impact load is discussed.

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A study on the inner structure of magnetorheological fluids by image processing

Muhammad A. Bramantya, Hiroki Takuma, Jun Kuroiwa and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (Japan Society of Applied Electromagnetics and Mechanics)  19 ( Supplement ) S228-S233 2011.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

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This paper would be elaborate experiment result of inner structure of MR fluid by means of visualization using optical microscope and CCD camera. The results show the rate of cluster formation is increase when the strength of magnetic field is increase, means that cluster formations are more robust and larger size for high magnetic field. The investigation of inner structure of MR fluids using image processing was successful. The growth of cluster formation is clearly seen in our image analysis. The cluster develops more robust when the magnetic field intensity is increase.

Improvement of sloshing analysis for magnetic fluid

Ken-ichi Ohno, Hayato Suzuki and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (Japan Society of Applied Electromagnetics and Mechanics)  19 ( Supplement ) S139-S144 2011.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

　View Summary

A magnetic fluid is a functional fluid under a magnetic field. A theoretical analysis of a sloshing of the magnetic fluid in a cylindrical container is carried out. Vertical and horizontal components of the magnetic field are considered in the sloshing analysis. The magnetic field is assumed nonuniform and axsymmetric. A natural sloshing frequency of the magnetic fluid in the cylindrical container is obtained. It is found from the analysis that the natural sloshing frequency is affected by field gradients of both vertical and horizontal components of the magnetic field. An experiment using a tuned magnetic fluid damper is also carried out to measure a change of the natural sloshing frequency by the magnetic field. The analysis of present paper is confirmed by using the experimental results.


Numerical investigation on the performance of Wells turbine with non-uniform tip clearance for wave energy conversion

Zahari Taha, Sugiyono, T.M.Y.S. Tuan Ya, and Tatsuo Sawada

Applied Ocean Research (Elsevier)  33 ( 4 ) 321-331 2011.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0141-1187

　View Summary

The performance of a Wells turbine with various non-uniform tip clearances was investigated using computational fluid dynamics. The investigation was performed on numerical models of a NACA0020 blade profile under steady flow conditions. The performance of turbines with uniform and non-uniform tip clearances was compared. It was shown that the performance of turbine with non-uniform tip clearance is similar with that of turbine with uniform one in terms of torque coefficient, input power coefficient, and efficiency. However, the turbine with non-uniform tip clearance seems to have a preferable overall performance. An investigation on the flow-field around the turbine blade was performed in order to explain the phenomena.

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Analysis of liquid sloshing of a tuned magnetic fluid damper for single and co-axial cylindrical containers

Ken-ichi Ohno, Hayato Suzuki and Tatsuo Sawada

Journal of Magnetism and Magnetic Materials (Elsevier)  323 ( 10 ) 1389-1393 2011.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

　View Summary

The magnetic fluid sloshing in a coaxial cylindrical container was analyzed theoretically under the axisymmetrical magnetic field. The theoretical results showed that a radial component of the magnetic field also changed the natural sloshing frequency. A policy of the suitable design of the TMFD was presented and the effect of the radial component of the magnetic field was verified experimentally.

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The influence of magnetic field swept rate on the ultrasonic propagation velocity of magnetorheological fluids

Muhammad Agung Bramantya and Tatsuo Sawada

Journal of Magnetism and Magnetic Materials (Elsevier)  323 ( 10 ) 1330-1333 2011.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

　View Summary

We measured ultrasonic propagation velocity in MR fluid influenced by an external magnetic field for different swept rate precisely. With increasing magnetic field intensity, the changes of the ultrasonic wave velocity are more pronounced. Sedimentation effect takes place in certain time for different swept rate due to magnetic particle size and it follows linear relationship in log scale. Significant differences of the ultrasonic wave velocity are established between the case when the field is swept at a constant rate and the case when it is stepped up.

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Characteristics of hydrodynamic pressure of a magnetic fluid in a tuned magnetic fluid damper

Ken-ichi Ohno and Tatsuo Sawada

Materials Science Forum (Trans Tech Publications, Switzerland)  670   181-190 2010.12

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1662-9752

　View Summary

A characteristic of the tuned magnetic fluid damper (TMFD) is to change a natural frequency of a sloshing. When a magnetic field is applied to a container filled with a magnetic fluid from below, the natural sloshing frequency increases and a range of a damping frequency is spread. In this paper, pressure measurements were used to control the appropriate magnetic field.

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Ultrasonic investigation of the effect of volume fraction on the clustering structures of magneto-rheological fluids

Muhammad Agung Bramantya, Hiroki Takuma, Jun Kuroiwa and Tatsuo Sawada

Materials Science Forum (Trans Tech Publications, Switzerland)  670   198-206 2010.12

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1662-9752

　View Summary

We propose a qualitative investigation of these volume fraction effects by measuring properties of ultrasonic wave propagation velocity in magnetorheological fluids (MRF), having various volume fractions. The ultrasonic wave propagation velocity changes under the effect of an external magneticfield as a result of arrangement of clusters along the direction of the field in the MRF.

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Effect of magnetic field on heat transfer in rectangular duct flow of a magnetic fluid

Masaaki Motozawaa, Jia Changa, Tatsuo Sawada, Yasuo Kawaguchi

Physics Procedia (Elsevier)  9   190-193 2010.11

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1875-3892

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Effect of magnetic field on heat transfer in rectangular duct flow of a magnetic fluid was investigated experimentally. Experiment was performed with changing Reynolds number based on the hydraulic diameter, magnetic field and heat flux. As a result of this experiment, heat transfer coefficient increases locally in the region where magnetic field exists. This heat transfer coefficient becomes large with increasing magnetic field intensity.

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Hysteresis phenomena of ultrasonic velocity change in magnetorheological fluids

Muhammad Agung Bramantya, Hiroki Takuma and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  33 ( 3-4 ) 1365-1372 2010.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

　View Summary

The magnetorheological response of magnetorheological fluids (MRF) results from the polarization induced in the suspended particles by application of an external magnetic field. We proposed a qualitative analysis of these effects by measuring properties of ultrasonic propagation. Hysteresis was appeared when magnetic field increased to and decreased from the certain value, 290 mT in our experiment. The change rate of the ultrasonic wave propagation velocity increased during the increasing process of the external magnetic field. However, it was kept almost the same value during the decreasing process.

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An effect of vertical sloshing on a fluid pressure and a surface displacement in a tuned magnetic fluid damper

Ken-ichi Ohno and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  33 ( 3-4 ) 1411-1416 2010.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

　View Summary

A magnetic fluid damper (TMFD) uses hydrodynamic force of sloshing of a magnetic fluid to dampen oscillation. Hydrodynamic force and displacement of surface of the fluid in the TMFD change according to the forced amplitude. Hydrodynamic force changes linearly with surface displacement. The changing rate between hydrodynamic force and surface amplitude varies around a characteristic forced frequency.

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Ultrasonic propagation velocity in magnetic and magnetorheological fluids due to an external magnetic field

Muhammad Agung Bramantya, Masaaki Motozawa and Tatsuo Sawada

Journal of Physics: Condensed Matter (IOP Publishing)  22 ( 32 ) 324102(5pp) 2010.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0953-8984

　View Summary

We measured ultrasonic propagation velocity in a hydrocarbon-based MF and MRF precisely. Based on these results, the clustering structures of these fluids are analyzed experimentally in terms of elapsed time dependence, effect of external magnetic field strength, angle and hysteresis phenomena. A comparison of ultrasonic velocity propagation between MF and MRF is discussed.

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A comparison of computational and experimental results of Wells turbine performance for wave energy conversion

Zahari Taha, Sugiyono and Tatsuo Sawada

Applied Ocean Research (Elsevier)  32 ( 1 ) 83-90 2010.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0141-1187

　View Summary

The investigation was performed on numerical models of a NACA0020 blade profile with various uniform tip clearances under steady flow conditions. The main objective of this investigation is to compare computational and experimental results, particularly for the cases of tip clearance to chord length ratio of 0.0056 and 0.0111. It was shown that there was good agreement between the computational and experimental results for both cases of tip clearance to chord length ratio in terms of torque and power coefficients, and efficiency. It was also shown clearly that the turbine performance is influenced significantly by tip clearance.

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Nonlinearity for fluid surface shape on a TMFD

Ken-ichi Ohno, Yuki Honjo and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  17 ( 3 ) 469-472 2009.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

　View Summary

The frequency response of a simple structure with a TMFD usually has two resonance frequencies and one best damping point. The frequency response is nonlinear because fluid sloshing is used. When a strong magnetic field is applied on a TMFD using one electromagnet, a bulge with many spikes is formed on the surface of the magnetic fluid. This bulge also affects nonlinearity. Frequency responses to magnetic fields with varying excitation amplitudes are obtained experimentally. Hardening or softening characteristics appear in resonant frequencies and the best damping point.

Ultrasonic propagation velocity in magneto rheological fluid under a uniform magnetic field

Muhammad Agung Bramantya, Hiroki Takuma, Mohd Faiz and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  17 ( 3 ) 433-436 2009.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

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We measured ultrasonic propagation velocity in an MR fluid precisely to study the cluster formation. Based on these results, the clustering structures of these fluids are analyzed experimentally in terms of time dependence, time interval, of-removal the magnetic field, and the angle of the magnetic field applied. The ultrasonic propagation velocity in an MR fluid change according to the magnetic field intensity, interval time and angle. The ultrasonic propagation velocity increases when a higher magnetic field is applied. The result also shows that the intensity of the external magnetic field has an influence on the ultrasonic propagation velocity even after the magnetic filed is removed. The ultrasonic velocity propagation also decreases when the interval time between application of the magnetic field and measurements increases.

Ultrasonic study on clustering structures of a magneto-rheological fluid under uniform magnetic fields

Muhammad Agung Bramantya, Hiroki Takuma and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  17 ( 2 ) 279-284 2009.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

　View Summary

The ultrasonic technique can be applied to an opaque fluid, such as MR fluid. The ultrasonic propagation velocity can be found by the pulsation methods. Based on these results, the clustering structures of these fluids are analyzed experimentally in term of elapsed time dependence, effect of the external magnetic field, effect of the after remove of the magnetic field, and hysteresis phenomena. It has been shown that MR fluid does not reach a new equilibrium state immediately when the external magnetic field is applied and after removed. Because the sizes of magnetic particle are relatively large in MR fluids, it is importance to consider the influence of sedimentation of the magnetic particles.

Influence of Inner Structure on Oscillating Pipe Flow of a Magnetic Fluid

Masaaki Motozawa, Ryo Hasegawa and Tatsuo Sawada

Transaction of The Japan Society of Mechanical Engineers, Ser.B (The Japan Society of Mechanical Engineers)  75 ( 753 ) 1013-1020 2009.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0387-5016

　View Summary

Oscillating pipe flow of a magnetic fluid was investigated experimentally by using the Ultrasonic Velocity Profiler (UVP) method. The test liquids are two kinds of water-based magnetic fluid W-40 and MSG11. UVP method is a useful technique for measuring the velocity components of a magnetic fluid. When this method is applied to magnetic fluid flow, it is necessary for the ultrasonic propagation velocity to be accurate. However, when an external magnetic field is applied to a magnetic fluid, some of the inner particles coagulate and form clustering structures. These clustering structures affect the ultrasonic propagation. Therefore, the properties of ultrasonic propagation in test magnetic fluids were also analyzed exactly before the measurement by UVP. Based on this analysis, UVP method is applied to magnetic fluid. In the result of velocity profile measurement, unique phenomena of oscillating pipe flow of the magnetic fluids subject to magnetic field were observed. It seems that the change of clustering structures under magnetic field cause these unique phenomena.

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Experimental analysis of clustering structures in magnetic and MR fluids using ultrasound

Muhammad Agung Bramantya, Masaaki Motozawa, Hiroki Takuma, Mohd Faiz and Tatsuo Sawada

Journal of Physics: Conference Series (IOP Publishing)  149   012040(4pp) 2009.03

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1742-6588

　View Summary

The formation of clustering structures in magnetic and MR fluids has an influence on ultrasonic propagation. We propose a qualitative analysis of these structures by measuring properties of ultrasonic propagation. Since magnetic and MR fluids are opaque, the noncontact inspection using this ultrasonic technique can be very useful for analyzing the inner structures of magnetic and MR fluids. We measured ultrasonic propagation velocity in a
hydrocarbon-based magnetic fluid and MR fluid precisely. Based on these results, the clustering structures of these fluids were analyzed experimentally in terms of elapsed time
dependence, effect of external magnetic field strength and angle, and hysteresis phenomena. A comparison of ultrasonic velocity propagation between magnetic and MR fluid was discussed.

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Responses of a Tuned Magnetic Fluid Damper to Change of Certain Parameters

Ken-ichi Ohno, Yuki Honjo and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  17 ( 1 ) 53-58 2009.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

　View Summary

A TMFD (Tuned Magnetic Fluid Damper) is a Tuned Liquid Damper using a magnetic fluid. Natural frequency of the TMFD can be controlled by a constant nonuniform magnetic field of vertical direction. Analysis of the TMFD is carried out by using a simple analogy model of a TMD (Tuned Mass Damper). We used two different cylindrical TMFDs, whose diameters are different. The experimental frequency responses are compared with approximation curves that are calculated under a condition of constant parameters of the TMD model. The approximation curve corresponds well to the experimental curve in smaller TMFD but does not well in larger TMFD. Frequency responses of some temperature of the magnetic fluid are obtained to know temperature dependency of the TMFD. Frequencies of resonance and a best damping point do not change but amplitudes of them are changed by the fluid temperature.

Influence of Inner Structure in a Magnetic Fluid on Ultrasonic Propagation

Masaaki Motozawa, Hiroki Takuma, Mohd Faiz, Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  17 ( 1 ) 47-52 2009.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

　View Summary

Experimental results for the properties of ultrasonic propagation velocity and attenuation in a kerosene-based magnetic fluid (EXP04019) are reported. The ultrasonic frequency used is 2MHz and the measurement scheme is based on the pulse method. The external magnetic field intensity is varied from 0mT to 550 mT and the angle between the magnetic field direction and the direction of ultrasonic wave propagation is adjusted from 0° to 90°. We observed various characteristic properties of ultrasonic propagation. The ultrasonic propagation velocity and attenuation change with the elapsed time of external magnetic field application and with magnetic field intensity. When the magnetic field is applied to magnetic fluid, some of the magnetic particles in the magnetic fluid form clustering structures. These structures cause the properties of ultrasonic propagation. We discussed influence of inner structure in magnetic fluid on ultrasonic propagation.

Velocity and attenuation of ultrasonic propagation in magnetic fluids under a uniform magnetic field

Masaaki Motozawa and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  28 ( 1-2 ) 143-148 2008.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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Velocity and attenuation of ultrasonic propagation in magnetic fluids subjected to a magnetic field are examined experimentally. Measurements are taken while changing the magnetic field intensity and the angle between the magnetic field direction and the ultrasonic propagation direction. The ultrasonic propagation velocity and attenuation are dependent on the intensity and the elapsed time of the magnetic field. When the magnetic field is applied to magnetic fluid, magnetic particles form clustering structures and they effect on ultrasonic propagation in a magnetic fluid. Based on experimental results, the influence of the inner structure of the magnetic fluids on the properties of ultrasonic propagation is discussed.

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Optimal design of a tuned liquid damper using a magnetic fluid with one electromagnet

Ken-ichi Ohno, Manabu Shimoda and Tatsuo Sawada

Journal of Physics: Condensed Matter (IOP Publishing)  20 ( 20 ) 204146(5pp) 2008.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0953-8984

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Characteristics of a tuned magnetic fluid damper (TMFD) are examined. An optimal depth of a magnetic fluid in a cylindrical container is calculated using a linear analysis of a magnetic fluid sloshing. In order to avoid swirling in lower depth fluids, several experiments using higher fluids depth are carried out and a good damping range is obtained.

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Experimental measurements of ultrasonic propagation velocity and attenuation in a magnetic fluid

Masaaki Motozawa, Yuta Iizuka and Tatsuo Sawada

Journal of Physics: Condensed Matter (IOP Publishing)  20 ( 20 ) 204117(5pp) 2008.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0953-8984

　View Summary

The ultrasonic propagation velocity and attenuation in a magnetic fluid subjected to the magnetic field are measured precisely. Various characteristic properties of ultrasonic propagation in magnetic fluid
such as hysteresis and anisotropy are observed. These results show that the ultrasonic propagation velocity and attenuation are dependent upon the intensity and the length of time that the magnetic field is applied. When the magnetic field is applied, some of the magnetic particles in the magnetic fluid form clustering structures that influence ultrasonic propagation in a magnetic fluid.

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Properties of ultrasonic propagation in functional fluids under magnetic fields

Masaaki Motozawa, Tatsuo Sawada and Yoshiyuki Matsumoto

International Journal of Modern Physics B (World Scientific)  21 ( 28-29 ) 4914-4921 2007.11

Research paper (scientific journal), Joint Work, Accepted

　View Summary

The properties of ultrasonic propagation velocity in water-based and kerosene-based magnetic fluids and an MR fluid are examined experimentally. The ultrasonic frequency used is 1 MHz and the measurement scheme is based on the pulse method. The external magnetic field intensity is varied from 0 mT to 550 mT and is swept at a constant rate dB/dt (sweep rate). The ultrasonic propagation velocity changes with applied magnetic field and hysteresis is observed. The properties of ultrasonic propagation seem to be highly influenced by the formation of chain-like clusters (in the magnetic fluids) and robust clusters (in the MR fluid).

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Characteristics of a tuned liquid damper using a magnetic fluid

Ken-ichi Ohno, Manabu Shimoda and Tatsuo Sawada

Proceedings of the 10th International Conference on Electrorheological Fluids and Magnetorheological Suspensions (World Scientific Publishing/University of Nevada, Reno)     459-466 2007.11

Research paper (international conference proceedings), Joint Work

　View Summary

The frequency response of a tuned liquid damper (TLD) which uses the sloshing of a magnetic fluid (a tuned magnetic fluid damper (TMFD)) is investigated. Effective mass, stiffness and damping are estimated from experimental results, using a single-degree-of-freedom tuned mass damper (TMD) analogy. TLD is a passive mechanical damper that uses sloshing liquid to dampen oscillations, but TMFD is semi-active damper because of application of magnetic field. We first compare results obtained by numerical simulation and experiment to show that a TMFD cannot be modeled by a simple analytical model based on analogy with TMD. Then we propose a new analytical model of TMFD and examine the validity of this new model experimentally.

Properties of ultrasonic propagation in functional fluids under magnetic fields

Masaaki Motozawa and Tatsuo Sawada

Proceedings of the 10th International Conference on Electrorheological Fluids and Magnetorheological Suspensions (World Scientific Publishing/University of Nevada, Reno)     248-255 2007.11

Research paper (international conference proceedings), Joint Work

　View Summary

The properties of ultrasonic propagation velocity in water-based and kerosene-based magnetic fluids and an MR fluid are examined experimentally. The ultrasonic frequency used is 1 MHz and the measurement scheme is based on the pulse method. The external magnetic field intensity is varied from 0 mT to 550 mT and is swept at a constant rate dB/dt (sweep rate). The ultrasonic propagation velocity changes with applied magnetic field and hysteresis is observed. The properties of ultrasonic propagation seem to be highly influenced by the formation of chain-like clusters (in the magnetic fluids) and robust clusters (in the MR fluid).

Two-layered magnetic fluid sloshing in a rectangular container

Shin-ichi Yoshida, Andrea Benvenuti, Kenji Tomita and Tatsuo Sawada

Proceedings of the 10th International Conference on Electrorheological Fluids and Magnetorheological Suspensions (World Scientific Publishing/University of Nevada, Reno)     551-556 2007.11

Research paper (international conference proceedings), Joint Work

　View Summary

The dynamic behavior of a two-layered fluid in a laterally oscillated rectangular container under a vertical nonuniform magnetic field was studied experimentally. The two-layered fluid was formed of water based magnetic fluid and silicone oil. The dynamic behavior was studied by measuring the velocity profile of the two-layered fluid using an ultrasound velocity profile measuring technique while varying the vertical magnetic field. The displacement of the free surface was measured using a laser sensor. The effect of the magnetic field on the sloshing of the two-layered fluid was considered.

Ultrasonic analysis of clustering structures in magnetic fluid under magnetic field

Masaaki Motozawa, Yuta Iizuka and Tatsuo Sawada

International Conference on Advanced Technology in Experimental Mechanics 2007 (The Materials & Mechanics Division of JSME)     1-5 2007.09

Research paper (conference, symposium, etc.), Joint Work, Accepted

　View Summary

Experimental results from studies on the properties of ultrasonic propagation velocity and attenuation in hydrocarbon-based magnetic fluid are reported. The ultrasonic frequency used is 2 MHz and the measurement scheme is based on the pulse method. The external magnetic field intensity is varied from 0 to 550 mT and the angle between the magnetic field direction and the direction of ultrasonic wave propagation is adjusted from 0 to 90°. The ultrasonic propagation velocity and attenuation changes are dependent upon the intensity of the magnetic field and the elapsed time of application. Characteristic properties of ultrasonic propagation in magnetic fluid are observed. These particular results seem to be caused by clustering structures in the magnetic fluid. Based on these results, the inner structure of the magnetic fluid is analyzed experimentally and the application of non-contact inspection in opaque fluids by ultrasonic techniques is discussed.

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Characteristic parameters of a tuned magnetic fluid damper under magnetic fields

Ken-ichi Ohno, Manabu Shimoda and Tatsuo Sawada

Proceedings of FEDSM2007, 5th Joint ASME/JSME Fluids Engineering Conference (ASME)     1-4 2007.08

Research paper (international conference proceedings), Joint Work, Accepted

　View Summary

Damping parameters of a tuned magnetic fluid damper [TMFD] using a tuned mass damper [TMD] analogy model are obtained from approximation to frequency responses of experiments used some sort of magnetic fluids in a cylindrical container. An effective mass is changed by a magnetic field from downside, however a significant change of surface shape of magnetic fluids causes strange changing tendency. It was found that other parameters are changed according to the surface shape.

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Investigation of inner structure in magnetic and MR fluids by ultrasonic propagation velocity

Masaaki Motozawa, Yuta Iizuka and Tatsuo Sawada

Proceedings of FEDSM2007, 5th Joint ASME/JSME Fluids Engineering Conference (ASME)     1-6 2007.07

Research paper (international conference proceedings), Joint Work, Accepted

　View Summary

When the magnetic field is applied to magnetic or MR fluids, some of inner particles form clustering structure. These clustering structures influence on the ultrasonic propagation velocity in these fluids. We measured precisely the properties of ultrasonic propagation velocity in these fluids subjected to the magnetic field. The measurement scheme is based on the pulse method. The external magnetic field intensity is varied from 0 mT to 550 mT and the angle between the magnetic field direction and the direction of ultrasonic wave propagation is varied from 0° to 90°. Some interesting properties of ultrasonic propagation such as hysteresis and anisotropy are observed. Based on the experimental results, the inner structures of the magnetic or the MR fluids are analyzed experimentally and the application of non-contact inspection in these fluids by ultrasonic techniques is discussed.

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Experimental measurement of ultrasonic propagation velocity and attenuation in magnetic fluids

Masaaki Motozawa, Yuta Iizuka and Tatsuo Sawada

The 12th Japanese-French Workshop on Magnetic Fluids (University Pierre et Marie Curie - Paris 6)   2007.07

Research paper (conference, symposium, etc.), Joint Work

　View Summary

We performed measurements of ultrasonic propagation velocity and attenuation in various magnetic fluids. These measurements were taken under changing external magnetic field intensity, direction of magnetic field, and time of applying magnetic field. Based on these results, influence of the chain-like cluster formation on ultrasonic propagation was discussed.

Influence of a uniform magnetic field on ultrasonic propagation velocities in magnetic fluids

Masaaki Motozawa, Yoshiyuki Matsumoto and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  25 ( 1-4 ) 133-138 2007.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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Experimental results for ultrasonic propagation velocity properties in water-based magnetic fluids are reported. Water-based magnetic fluid samples having 10 wt%, 30 wt% and 40 wt% concentration of magnetic particles were examined. The ultrasonic propagation velocity generally decreases with higher concentrations of magnetic particles, generally increases with increasing external magnetic field intensity and exhibits anisotropy.

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Effective method of applying magnetic field on a tuned liquid damper using a magnetic fluid

Shohei Horie, Manabu Shimoda, Ken-ichi Ohno, Jun Nakamura and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  25 ( 1-4 ) 139-143 2007.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

　View Summary

A new analytical model of a tuned liquid damper (TLD) using a magnetic fluid (tuned magnetic fluid damper (TMFD)) is proposed in order to better explain the unique damping characteristics of a TMFD. This model is then clarified experimentally using vertical magnetic fields and we investigate an effective method of applying a magnetic field on a tuned magnetic fluid damper (TMFD).

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Influence the chain-like cluster in a magnetic fluid on velocity profiles of the oscillating pipe flow

Ryo Hasegawa, Takashi Innami, Manabu Shimoda and Tatsuo Sawada

Journal of the Japan Society of Applied Electromagnetics and Mechanics (The Japan Society of Applied Electromagnetics and Mechanics)  14 ( 1 ) 21-26 2006.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0919-4452

　View Summary

Oscillating pipe flow of a magnetic fluid subject to a magnetic field was investigated experimentally. Time-dependent velocity profiles are obtained by UVP method. When the magnetic field is applied for some period before measurement, peculiar velocity profiles are obtained because of the growth of chain-like clusters in the magnetic fluid. The influence of the amount of time of pre-applying magnetic field and magnetic field intensity on flow behaviors are examined. The apparent flow rate is introduced to evaluate the correlation between the velocity profile and the growth of chain-like clusters. It is found that the rate of change of the apparent flow rate increases with both magnetic field intensity and the pre-application time of magnetic field.

Effect of external magnetic field on ultrasonic propagation velocity in magnetic fluids

Masaaki Motozawa, Yoshiyuki Matsumoto and Tatsuo Sawada

JSME International Journal, Ser.B (JSME)  48 ( 3 ) 471-477 2005.08

Research paper (scientific journal), Joint Work, Accepted

　View Summary

Experimental results for the properties of ultrasonic propagation velocity in kerosene-based and water-based magnetic fluids are reported. The ultrasonic propagation velocity in magnetic fluids is dependent on temperature, elapsed time of applying the magnetic field, and magnetic field intensity. Hysteresis and anisotropy of ultrasonic propagation velocity are observed. These interesting results seem to be related to chain-like cluster formation in the magnetic fluids and the characteristic period of Brownian motion of the magnetic particles.

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Influence of magnetic field on ultrasonic propagation velocity in magnetic fluids

Masaaki Motozawa and Tatsuo Sawada

Journal of Magnetism and Magnetic Materials (Elsevier)  289 ( 1-3 ) 66-69 2005.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

　View Summary

水ベースおよびケロシンベース磁性流体中を伝播する超音波特性の磁場依存性と異方性に関する実験を行い，超音波伝播特性を明らかにした。

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Velocity profile measurement of an oscillating pipe flow of a magnetic fluid

Yuki Oshikawa, Takeshi Innami and Tatsuo Sawada

Proceedings of ASME FEDSM'03, 4th ASME-JSME Joint Fluids Engineering Conference (ASME)     1-7 2003.07

Research paper (international conference proceedings), Joint Work, Accepted

　View Summary

Since UVP is the method to take the velocity information by using ultrasound, this method is very suitable for measuring the velocity profile of opaque fluid. Oscillating pipe flow of a magnetic fluid was investigated experimentally to examine the applicability of this method to magnetic fluid flow. We used a diluted water-base magnetic fluid and the magnetic field was applied by two permanent magnets. Influence of an applied magnetic field on flow behaviors were discussed. The amplitude and phase of the oscillating velocity varied with intensity of the magnetic field, which yielded increase of the apparent viscosity.

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Characteristics of iltrasound propagation in a magnetic fluid under uniform magnetic field

Masaaki Motozawa and Tatsuo Sawada

Proceedings of ASME FEDSM'03, 4th ASME-JSME Joint Fluids Engineering Conference (ASME)     1-4 2003.07

Research paper (international conference proceedings), Joint Work, Accepted

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When an external magnetic field is applied to a magnetic fluid, some of the colloidal particles coagulate and form chain-like clusters. Properties of ultrasonic propagation wave are changed by these chain-like clusters. We carried out measurement of the ultrasonic propagation velocity in a magnetic fluid. Measurement were made by changing the magnetic field intensity from 0 mT to 570 mT, and the angle between the magnetic field direction and direction of the ultrasound propagation from 0° to 180°. The ultrasound frequencies were 1 MHz, 2 MHz and 4 MHz. Some of experimental results for the characteristics of ultrasound propagation in a magnetic fluid under a uniform magnetic field were reported.

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Effect of magnetic field on a tuned liquid damper using a magnetic fluid

Yasuhiro Ohira, Hiroshi Houda and Tatsuo Sawada

International Journal of Applied Electromagnetics and Mechanics (IOS Press)  13 ( 1-4 ) 71-78 2002.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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The frequency response of a tuned liquid damper (TLD) which uses a magnetic fluid (called a "tuned magnetic fluid damper" (TMFD)) is investigated. A single-degree-of-freedom tuned mass damper (TMD) analogy is used to define the effective mass, stiffness and damping and these parameters are then estimated from experimental results. A numerical simulation is used to examine the TMFD and appropriate magnetic field conditions for effective damping are predicted. In particular, the performance of the TMFD was improved by switching the applied magnetic field at a point near the resonant frequency of the undamped structure.

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Influence of a magnetic field on ultrasound propagation in a magnetic fluid

Tatsuo Sawada, Hiroyuki Nishiyama and Takashi Tabata

Journal of Magnetism and Magnetic Materials (Elsevier)  252 ( 1-3 ) 186-188 2002.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

　View Summary

Experimental results for anisotropy and hysteresis of the ultrasonic propagation velocity(1 MHz) in a magnetic fluid subject to a magnetic field are reported. Measurements were made by the pulse method while the magnetic field intensity was varied from 0 mT to 570 mT and the angle between the magnetic field direction and the direction of ultrasonic wave propagation was varied between 0 deg and 180 deg. Some interesting results that seem to be caused by cluster formation in the magnetic fluid were obtained.

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Nonlinear shape oscillations of axisymmetric magnetic fluid columns in a magnetic field

Motoyoshi Ohaba, Yuko Suzuki, Tatsuo Sawada, Yu-Zhou Liu, Masaaki Takeuti and Takahiko Tanahashi

Journal of Magnetism and Magnetic Materials (Elsevier)  252 ( 1-3 ) 306-308 2002.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

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Nonlinear axisymmetric shape oscillations have been revealed through experiments conducted with large-amplitude forced vertical vibrations of a magnetic fluid column supported by a magnetic field in the presence of gravity. Those nonlinear shape oscillations are characterized by the jumping phenomena, mode transition, and subharmonic motions.

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Sloshing behavior of a magnetic fluid in a cylindrical container

Tatsuo Sawada, Yasuhiro Ohira and Hiroshi Houda

Experiments in Fluids (Springer)  32 ( 2 ) 197-203 2002.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0723-4864

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Sloshing of a magnetic fluid in a laterally vibrated cylindrical container subject to a non-uniform vertical magnetic field was examined. Internal velocity profiles were measured using ultrasound Doppler velocimetry. The effect of the magnetic field on the resonant frequency of the fluid-container system was examined and the results were compared with theoretical results. The second and third peak of the power spectra of velocity shifted to a low frequency region as the magnetic field was increased. It was observed that these derived frequency peaks were connected with swirling in the cylindrical container.

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Sloshing motion of a magnetic fluid in a cylindrical container due to horizontal oscillation

Tatsuo Sawada, Yasuhiro Ohira and Hiroshi Houda

Energy Conversion and Management (Pergamon)  43 ( 3 ) 299-308 2002.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0196-8904

　View Summary

Sloshing is a phenomenon that occurs when a liquid with a free surface is severely agitated in a liquid storage container. In an axisymmetric container, even though the excitation is lateral, the liquid oscillates with rotational movement around the central axis of the container. This phenomenon is called swirling and may be unstable swirling or stable swirling. We measure the velocity profile of a sloshing magnetic fluid using an ultrasonic Doppler velocimetry method called UVP, and examine the relationship between internal velocity profiles and swirling phenomena, in particular, stable swirling phenomena. We calculated power spectra from the velocity data using a fast Fourier transform and observed that the most dominant peak in the power spectrum moved to higher frequencies as the magnetic field intensity was increased, whereas a derived peak at a lower frequency moved to lower frequencies as the magnetic field intensity was increased.

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elocity Profile Measurement on Oscillating Pipe Flow of a Magnetic Fluid by UVP Method

Gentaro Yamanaka, Hiroshige Kikura, Yasushi Takeda, Tatsuo Sawada and Masanori Aritomi

Transaction of The Japan Society of Mechanical Engineers, Ser.B (The Japan Society of Mechanical Engineers)  67 ( 663 ) 2717-2724 2001.11

Research paper (scientific journal), Joint Work, Accepted

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This paper presents velocity profile measurements of an oscillatory pipe flow of magnetic fluid by Ultrasonic Velocity Profile (UVP) method. Experiments are performed at Reynols number Rc=367, defined by mean velocity amplitude and a pipe diameter, and non dimensional angular frequency W=4.76. It is shown that velocity amplitude increases in the center of a pipe and decreases in the near wall region under non-uniform magnetic field. The comparison of measured data under non magnetic field with those obtained from the theory of Newtonian-fluid reveals that noticeable discrepancies exist between them.

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Large-amplitude axisymmetric mode oscillations of a magnetic fluid column supported by a magnetic field

Motoyoshi Ohaba, Yuko Suzuki, Masaaki Takeuchi, Tatsuo Sawada, Seiichi Sudo, Takahiko Tanahashi

Journal of the Japan Society of Microgravity Application (Japan Society of Microgravity Application)  18 ( 4 ) 269-275 2001.10

Research paper (scientific journal), Joint Work, Accepted

　View Summary

Axisymmetric mode oscillations of a magnetic fluid column supported by a magnetic field are examined experimentally in the presence of gravity. A magnetic fluid column, height 9.78 mm, is formed vertically in a magnetic field generated by Helmholtz like coils fastened on an electrodynamic exciter, and vibrated vertically to produce axisymmetric oscillations. Nonlinear jumping phenomena, transition from the (0, 1) mode standing wave to the progressive wave and mode coupling are observed at larger amplitude oscillations. One-half subharmonic oscillations such as the (3, 1), (4, 1) and (5, 1) modes arise beyond some threshold values of the excitation amplitude. These new phenomena are useful to discuss the liquid column oscillations in a microgravity environment in the Floating Zone Technique.

Visualization of natural convection of different unmixed liquids in a cubic container

Saiguang Wang, Tatsuo Sawada, Takahiko Tanahashi

Transactions of the Visualization Society of Japan (Visualization Society of Japan)  21 ( 1 ) 6-11 2001.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1346-5252

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Natural thermal convection of different unmixed liquids is quite different from that of a single liquid because of the existence of liquid-liquid interface. In order to clarify this phenomenon, it is necessary to know both flow and temperature fields of different unmixed liquids. In the present paper, natural convection of different unmixed liquids in a cubic enclosure with isothermal hot and cold walls was investigated. Influence of difference of kinematic viscosities and volume ratio of two liquids on flow and temperature fields were experimentally studied. Temperature distribution on a central cross section was visualized by thermosensitive liquid crystal particles. The conclusions derived from the above experiment are as follows: As the thermal movement occur through the interface, The reverse speed of two kind of liquids near the interface was promoted. And beside the main circulation that occurred in the liquids of higher volume ratio and lower viscosity ratio, the secondary circulation was caused in the upper liquid.

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Numerical investigation of the turbulent structure in periodic pipe flow

Hideo Udagawa and Tatsuo Sawada

ASME PVP-Vol.414-2, Emerging Technologies in Fluids, Structures, and Fluid/Structure Interactions (ASME)     99-105 2000.07

Research paper (international conference proceedings), Joint Work, Accepted

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円管内振動流をDNSによって解析を行い，特に壁近傍の乱流特性を明らかにした。

Visualization of clustering on non-magnetic and ferromagnetic particles in magnetic fluids

Tatsuo Sawada, Hiroshige Kikura, Gentaro Yamanaka, Mitsuo Matsuzaki, Isao Nakatani and Masanori Aritomi

Proceedings of SPIE Conference on Optical Diagnostics for Fluids /Heat/Combustion and Photomechanics for Solids (The International Society for Optical Engineering)  3783   389-396 1999.10

Research paper (international conference proceedings), Joint Work

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Micro-cluster formation of the non-magnetic and ferromagnetic particles in a magnetic fluid was investigated. Using an optical microscope system with cardioid condenser lens, real-time visualization of the Brownian motions of both particles were carried out. The chain-like cluster formation of both particles were observed simultaneously under the magnetic field. Two types of magnetic fluid of a water-based and kerosene-based magnetic fluids were used as test liquids.

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Shape oscillations of magnetic liquid columns subject to vertical vibrations

Motoyoshi Ohaba, Tuneyoshi Sugimoto, Tatsuo Sawada, Takahiko Tanahashi and Seiichi Sudo

Proceedings of the 3rd ASME/JSME Joint Fluids Engineering Conference (ASME)  FED-248 1999.07

Research paper (international conference proceedings), Joint Work, Accepted

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Shape oscillations of magnetic liquid columns subject to vertical vibration in a uniform magnetic field are examined in the presence of gravity. A magnetic liquid column is formed vertically against gravity in an axial magnetic field produced by Helmholtz coils and then vibrated to produce axisymmetric oscillations. A high-speed video camera is used to observe the column's dynamic shape and two high-resolution laser displacement detectors measure the amplitudes of both the exciter table and the column interface. The experimental interfacial amplitude shows good agreement with our theoretical predictions. Two new wave motions are observed: a progressive wave near the resonance range of the fundamental mode (0,1), and a mode (4,1) azimuthal one-half subharmonic oscillation beyond the mode (0,1) frequency. These are the first observations of such wave motions in a terrestrial experiment and may suggest similar liquid column oscillations in a microgravity environment.

Velocity profile measurements of magnetic fluid flow using ultrasonic Doppler method

Hiroshige Kikura, Yasushi Takeda and Tatsuo Sawada

Journal of Magnetism and Magnetic Materials (Elsevier)  201 ( 1-3 ) 276-280 1999.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

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In the present study, successful applications of the ultrasound velocity profile measuring technique to velocity fields of a magnetic fluid are presented. After a brief introduction of its principle, various examples applied for the magnetic fluid flow are demonstrated.

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Oscillations of magnetic liquid columns subject to random vibration

Motoyoshi Ohaba, Tsuneyoshi Sugimoto, Tatsuo Sawada, Seiichi Sudo and Takahiko Tanahashi

Journal of Magnetism and Magnetic Materials (Elsevier)  201 ( 1-3 ) 293-296 1999.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

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The interfacial impulse response of the axisymmetric mode (0,1) of a finite liquid column in a microgravity environment is simulated using magnetic liquids and random vibration.

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Dynamic characteristic of a magnetic fluid column formed by magnetic field

Nobuaki Omura, Katsuhiro Yamashita, Tatsuo Sawada and Motoyoshi Ohaba

Journal of Magnetism and Magnetic Materials (Elsevier)  201 ( 1-3 ) 297-299 1999.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

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This paper examines the dynamic characteristics of liquid columns when lateral sinusoidal vibration is applied. The first, second and third resonant frequencies shift to a higher frequency region as the magnetic field intensity increases. For a magnetic fluid column, the second and third resonant frequencies show interesting behavior as the magnetic field is varied.

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Kinematic characteristics of magnetic fluid sloshing in a rectangular container subject to non-uniform magnetic fields

Tatsuo Sawada, Hiroshige Kikura and Takahiko Tanahashi

Experiments in Fluids (Springer)  26 ( 3 ) 215-221 1999.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0723-4864

　View Summary

The dynamic behavior of a magnetic fluid in a laterally vibrated rectangular container subject to a non-uniform vertical magnetic field has been investigated. Flow behavior was observed using the ultrasound velocity profile measuring technique. The effect of the magnetic field on the resonant frequency of the fluid-container system is discussed. Experimental results are compared with the results obtained from nonlinear theory using the perturbation method.

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Magnetic field effects on axisymmetrically oscillating magnetic liquid columns

Motoyoshi Ohaba, Tsuneyoshi Sugimoto, Tatsuo Sawada, Seiichi Sudo and Takahiko Tanahashi

Journal of Japan Society of Micrograbity Application (Japan Society of Micrograbity Application)  15 ( SupplementII ) 243-248 1998.12

Research paper (scientific journal), Joint Work, Accepted

　View Summary

磁性流体の液柱の軸対称振動におよぼす磁場の効果を調べた。

Kinematic characteristics of magnetic fluid sloshing in a rectangular container subject to non-uniform magnetic fields

Tatsuo Sawada, Hiroshige Kikura and Takahiko Tanahashi

PSI Proceedings 98-01, Selected Papers of the First International Symposium on Ultrasonic Doppler Methods in Fluid Mechanics and Fluid Engineering (Paul Scherrer Institut)     207-227 1998.08

Research paper (conference, symposium, etc.), Joint Work

　View Summary

The dynamic behavior of a magnetic fluid in a laterally vibrated rectangular container subject to a non-uniform vertical magnetic field has been investigated. Flow behavior was observed using the ultrasound velocity profile measuring technique. The effect of the magnetic field on the resonant frequency of the fluid-container system is discussed. Experimental results are compared with the results obtained from nonlinear theory using the perturbation method.

Magnetic field effects on wave motion of a magnetic liquid

Motoyoshi Ohaba, Masatsugu Tomonori, Tatsuo Sawada, Seiichi Sudo and Takahiko Tanahashi

Studies in Applied Electromagnetics and Mechanics, Nonlinear Electromagnetic Systems 13   855-858 1998.07

Research paper (international conference proceedings), Joint Work, Accepted

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磁性流体液柱が振動する場合に液柱表面に生じる表面波動の様子を実験的に調べて，印加磁場と加振周波数との関係を明らかにした。

Axisymmetric oscillation of magnetic liquid columns in a magnetic field

Motoyoshi Ohaba, Tatsuo Sawada, Masatsugu Tomonori, Seiichi Sudo and Takahiko Tanahashi

Studies in Applied Electromagnetics and Mechanics, Nonlinear Electromagnetic Systems 13   863-866 1998.07

Research paper (international conference proceedings), Joint Work, Accepted

　View Summary

軸対象モードでの磁性流体液柱の振動特性を調べ，理論解析結果との比較検討を行った。

Lateral vibration of a magnetic fluid column

Tatsuo Sawada, Yasuhiro Fujiwara, Nobuaki Omura, Motoyoshi Ohaba and Takahiko Tanahashi

Studies in Applied Electromagnetics and Mechanics, Nonlinear Electromagnetic Systems 13   871-874 1998.07

Research paper (international conference proceedings), Joint Work, Accepted

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Dynamic behavior of a magnetic fluid column which is formed between two electromagnets is investigated. An electrodynamic shaker is used to generate a lateral sinusoidal vibration. Experiments are carried out to clarify the influence of magnetic field intensity, column height and fluid volume on the vibration of a magnetic fluid column. A theoretical approach is also taken using linearized wave theory. The first resonant frequency of displacement of the free surface increases with the magnetic field intensity, and decreases with the radius and height of the magnetic fluid column. These results are in good agreement with theoretical results.

Ultrasound velocity profile measurement of a magnetic fluid flow caused by rotating magnetic field

Takahiro Handa, Tatsuo Sawada and Gentaro Yamanaka

Proceedings of the 1998 ASME Fluid Engineering Division Summer Meeting (ASME)  FED-245 1998.06

Research paper (international conference proceedings), Joint Work, Accepted

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Magnetic fluid is a stable suspension of solid magnetic particles and is an opaque fluid. This paper presents an application of the Ultrasound Velocity Profile monitor in measuring flow of a magnetic fluid in a cylindrical container. Velocity profiles of rotating flow of a magnetic fluid caused by an applied magnetic field were measured by UVP method and the 3-D flow structure was clarified.

Magnetic fluid simulation of liquid column oscillations in microgravity

Motoyoshi Ohaba, Yu Zhou Liu, Tatsuo Sawada and Takahiko Tanahashi

Proceedings of the 1998 ASME Fluid Engineering Division Summer Meeting (ASME)  FED-245 1998.06

Research paper (international conference proceedings), Joint Work, Accepted

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磁性流体液柱を用いた微小重力場での液柱振動現象の模擬実験を行った。そして，その模擬実験の有効性を明らかにした。

Axisymmetric interfacial oscillations of a magnetic fluid column

Motoyoshi Ohaba, Tatsuo Sawada, Shinpachiro Saito, Seiichi Sudo and Takahiko Tanahashi

JSME International Journal, Ser.B (JSME)  41 ( 2 ) 511-517 1998.05

Research paper (scientific journal), Joint Work, Accepted

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This paper presents the stability and dynamic characteristics of an axisymmetrically oscillating magnetic liquid column subjected to a uniform magnetic field in the presence of gravity. Initially, the axisymmetric mode response of a magnetic liquid column is analyzed using potential theory based on a magnetic field perturbation method. Then, an experiment is described in which a liquid column is formed between Helmholtz coils and vibrated vertically to produce axisymmetric oscillations by an electodynamic exciter. The surface frequency response of the column is measured optically using a high-speed video camera, a strobovision-snalyzer and a stroboscope. The results show that the magnetic field exerts a stabilizing effect on the column and the resonance frequency increases for increased liquid column aspect ratio(diameter / height). Both the experimental interfacial response and resonance frequency show good agreement with the theoretical prediction.

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Lateral vibrational characteristics of a magnetic liquid column held by magnetic field

Motoyoshi Ohaba, Tatsuo Sawada, Shin-Hachiro Saito, Seiichi Sudo, Takahiko Tanahashi

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  63 ( 612 ) 2725-2731 1997.08

Research paper (scientific journal), Joint Work, Accepted

　View Summary

We have investigated the stability and vibrational response of magnetic liquid columns held by Helmholtz coils. Theoretical resonance frequencies were derived from the linear potential theory prior to the experiment. During the experiment, a small quantity of a kerosene-based magnetic liquid was injected onto a lower pole plate. When the magnetic field was increased. a cylindrical column (height=9.78mm) was vertically formed between the two pole faces of the iron core Helmholtz coils. When the magnetic field was decreased, the column diameter exhibited hysteresis such that the column broke at a smaller diameter than that at formation. The coils holding the liquid column were then excited horizontally and the lowest mode (m=1, n=1) derived theoretically appeared in the measurements. The surface frequency response was measured optically using a CCD camera, a strobovision analyzer and a stroboscope for various magnetic field intensities and aspect ratios (mean diameter/height). We found that the resonance frequency of the mode (m=1, n=1) decreased with increase of the aspect ratio. The experimental resonance frequencies were in qualitative agreement with the theoretical predictions.

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Axisymmetric surface oscillations of a magnetic liquid column

Motoyoshi Ohaba, Tatsuo Sawada, Shin-hachiro Saito, Seiichi Sudo and Takahiko Tanahashi

JSME Contennial Grand Congress, Proceedings of International Conference on Fluid Engineering (JSME)  1   263-268 1997.07

Research paper (conference, symposium, etc.), Joint Work

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垂直加振される磁性流体液柱の振動モードを理論的に明らかにし，実験結果と比較検討し，理論解析の有効性を確かめた。

Magnetic field effects on a laterally vibrating magnetic liquid column

Motoyoshi Ohaba, Shinpachiro Saito, Seiichi Sudo, Tatsuo Sawada and Takahiko Tanahashi

ASME Transport Phenomena in Material Processing and Manufacturing (ASME)  HTD-336/FED-240   207-213 1996.11

Research paper (international conference proceedings), Joint Work, Accepted

　View Summary

The magnetic field effects on both the static stability limit and the resonance frequency of a magnetic liquid column are examined theoretically and experimentally. We first derived the theoretical resonance frequency of a column using linear potential theory. Then, in the experiment, a vertical cylindrical magnetic liquid column was formed between two electromagnets. As the magnetic field intensity was decreased, the column's diameter exhibited hysteresis, such that its stability limit extended to a smaller diameter range due to the coaxial magnetic field. The column was also subjected to lateral excitation and the surface frequency response of the non-axisymmetric first two modes were observed. It was found that the resonance frequency of the column increases with increasing magnetic field intensity and decreases with an increase in the aspect ratio of the column (mean diameter / height). The resonance frequency of the first mode was in qualitative agreement with the theory.

Vibration characteristics of a magnetic liquid bridge subject to a collinear magnetic field

Motoyoshi Ohaba, Tatsuo Sawada, Seiichi Sudo, Shinpachiro Saito and Takahiko Tanahashi

Studies in Applied Electromagnetics and Mechanics, Nonlinear Electromagnetic Systems 10   410-413 1996.10

Research paper (international conference proceedings), Joint Work, Accepted

　View Summary

非一様磁場下において水平加振を受ける磁性流体液柱の振動特性の線形理論解析を行った。そして，その解析結果を実験結果と比較し，両者が良好に一致する事を確認した。

磁性流体の立方体容器内自然対流のデータベース

棚橋隆彦，木倉宏成，澤田達男

日本機械学会RC124流れ解析データベース研究分科会研究報告書 (日本機械学会)     103-109 1996.07

Research paper (conference, symposium, etc.), Joint Work

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数値解析結果検討のための実験結果をデータベースとして提供した。

Effect of rotating magnetic field on natural convection of a magnetic fluid in horizontal cylindrical annuli

Tatsuo Sawada, Yasuhiro Matsubara, Toru Ueda, Naoki Ohta and Takahiko Tanahashi

Flow Visualization VII, Proceedings of the Seventh International Symposium on Flow Visualization    970-976 1995.09

Research paper (international conference proceedings), Joint Work

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We report that thermomagnetic convection of a magnetic fluid in concentric annuli made of two isothermal horizontal cylinders. Rotating magnetic field was applied by a three-phase induction motor. A thermosensitive liquid crystal was utilized in order to visualize wall-temperature distributions. A new parameter was introduced to understand heat transfer mechanism of the thermomagnetic convection. Influences of rotating magnetic field on distributions of the wall-temperature and Nusselt numbers were investigated precisely and characteristics of heat transfer of a magnetic fluid were discussed.

Flow of a magnetic fluid between concentric annuli (Rheological property of water-based magnetic fluid)

Makoto Momoi, Tatsuo Sawada and Takahiko Tanahashi

JSME International Journal, Ser.B (JSME)  38 ( 3 ) 360-365 1995.08

Research paper (scientific journal), Joint Work, Accepted

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We experimentally studied shear flow of a water-based magnetic fluid between concentric annuli. The experiment was carried out by changing the angular velocity of the outer cylinder, and the moment acting on the inner cylinder was measured. Experimental results were discussed in the following three ways. At first the magnetic fluid was treated as a Newtonian fluid, and a small difference in the flow curves was found. Next the power-law fluid theory was applied in order to explain these differences. Finally we examined this flow problem using the micropolar theory, which gives the theoretical relation between the moment acting on the inner cylinder and the angular velocity of the outer one. We measured the coefficient which denoted the micropolar effect, and showed the influence of the substructure on the fluid.

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Surface behaviors of the two-layers liquid sloshing under non-uniform magnetic field

Fumikazu Matsuura, Yasuhiro Matsubara,Tatsuo Sawada and Takahiko Tanahashi

Elsevier Studies in Applied Electromagnetics in Materials, Advanced Computational and Design Techniques in Applied Electromagnetic Systems (Elsevier)  6   517-520 1995.01

Research paper (international conference proceedings), Joint Work, Accepted

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The surface behaviors of the two-layers liquid in a laterally oscillating rectangular container were studied. A water-based magnetic fluid and a silicone oil were used in the experiments. A vertical non-uniform magnetic field was applied to the container. The resonant frequency of the fluids-container system moved toward the high frequency region with the magnetic field intensity in the same way of a single magnetic fluid.

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Circular flow of a magnetic fluid between coaxial cylinders

Kensuke Kawanaka, Tatsuo Sawada and Takahiko Tanahashi

Elsevier Studies in Applied Electromagnetics in Materials, Advanced Computational and Design Techniques in Applied Electromagnetic Systems (Elsevier)  6   513-516 1995.01

Research paper (international conference proceedings), Joint Work, Accepted

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Circular flow of a magnetic fluid between coaxial cylinders under a rotating magnetic field was studied experimentally. The moment acting on an inner cylinder was measured when an outer cylinder rotated. Experimental results were arranged for several parameters: directions of the rotation of magnetic field and the outer cylinder, the magnetic field intensity, radial gap between the cylinders.

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Visualization of wall temperature distribution caused by natural convection of magnetic fluids in a cubic enclosure

Tatsuo Sawada, Hiroshige Kikura and Takahiko Tanahashi

International Journal of Applied Electromagnetics in Materials (IOS Press)  4 ( 4 ) 329-335 1994.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1383-5416

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This paper presents experimental results on natural convection of magnetic fluids in a cubic enclosure with isothermal hot and cold walls under magnetic fields. The vertical magnetic fields were applied uniformly and nonuniformly using a permanent magnet and a electromagnet, respectively. Temperature distributions on a front wall were visualized by a thermosensitive liquid crystal. The horizontal temperature distributions on the central cross-section and Nusselt numbers were measured. The effects of uniform and non-uniform magnetic fields on the heat transfer and natural convection flow were discussed in detail.

Liquid sloshing of a magnetic fluid in a rectangular container

Tatsuo Sawada, Shuntaro Shibata, Yasuhiro Matsubara, Hiroshige Kikura and Takahiko Tanahashi

Transaction of The Japan Society of Mechanical Engineers, Ser.B (The Japan Society of Mechanical Engineers)  60 ( 572 ) 1250-1255 1994.04

Research paper (scientific journal), Joint Work, Accepted

　View Summary

The dynamic behavior of a magnetic fluid in a laterally oscillated rectangular container was studied experimentally. Frequency responses of magnetic fluid-container system were measured under vertical non-uniform magnetic fields. Relations between the resonant frequency and the applied magnetic field were discussed, and experimental results were characterized by Froude number with consideration of the magnetic effect. Since the apparent viscosity of the magnetic fluid increases with magnetic field, its effect on sloshing phenomenon was examined in detail. Internal pressure on the wall and displacement of surface waves were simultaneously displacement.

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Shear flow of a magnetic fluid between concentric annuli

Makoto Momoi, Tatsuo Sawada and Takahiko Tanahashi

Elsevier Studies in Applied Electromagnetics in Materials, Simulation and Design of Applied Electromagnetic Systems (Elsevier)  5   469-472 1994.01

Research paper (international conference proceedings), Joint Work, Accepted

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The authors studied a shear flow of a water-based magnetic fluid between concentric annuli experimentally. The outer cylinder is rotates at the constant speed(0-160 rpm). The inner cylinder is hung by the small stainless wire. Magnetic field was applied by a two pole three-phase induction motor. Experiments are largely divided into two parts. One is to clarify the rheological properties without magnetic field. The other is to make it clear how large the moment, which is acting on the inner cylinder, becomes under the magnetic field. Experimental results were discussed using power law theory and micro-polar theory.

Effect of magnetic field on natural convection of magnetic fluids of magnetic fluids

Tatsuo Sawada, Hiroshige Kikura and Takahiko Tanahashi

Elsevier Studies in Applied Electromagnetics in Materials, Simulation and Design of Applied Electromagnetic Systems (Elsevier)  5   457-460 1994.01

Research paper (international conference proceedings), Joint Work, Accepted

　View Summary

Natural convection of a magnetic fluid is driven by the buoyancy force due to the difference in the fluid density and by the magnetic force. The purpose of this investigation is to examine the effect of uniformed and ununiformed magnetic fields on natural convection heat transfer of a magnetic fluid in a vertical square cavity. The vertical magnetic fields are applied uniformly and ununiformly using a permanent magnet and an electromagnet. Temperature distributions on a front wall is visualized by a thermosensitive liquid crystal sheet. The horizontal temperature distributions in the central cross-section of the cavity were measured with copper-constantan thermocouples.

Natural convection of a magnetic fluid in concentric horizontal annuli under nonuniform magnetic fields

Tatsuo Sawada, Hiroshige Kikura, Atsushi Saito and Takahiko Tanahashi

Experimental Thermal and Fluid Science (Elsevier)  7 ( 3 ) 212-220 1993.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0894-1777

　View Summary

Natural convection of a magnetic fluid in concentric annuli was investigated experimentally. A magnetic field was applied to the cylinders using a permanent magnet. When there was no magnetic field, ordinary natural convection was observed. When a magnetic field gradient was applied in the same direction as the gravity, a wall-temperature distribution was observed, as if an apparent gravity had increased; however, the clear influence of the magnetic field was not found. When a magnetic field gradient was applied in the opposite direction of the gravity, the reverse natural convection was observed. Consequently, even if the intensity of the applied magnetic field was small, it played an important role in natural convection and heat transfer of a magnetic fluid. It was recognized that natural convection of a magnetic fluid could be controlled by the application of a magnetic field.

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Flow of a Magnetic Fluid between Concentric Annuli: Rheological Property of Water-based Magnetic Fluid

Makoto Momoi, Tatsuo Sawada and Takahiko Tanahashi

Transactions of the Japan Society of Mechanical Engineers Ser.B (Japan Society of Mechanical Engineers)  59 ( 562 ) 1785-1790 1993.06

Research paper (scientific journal), Joint Work, Accepted

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The authors experimentally studied a shear flow of a water-based magnetic fluid between concentric annuli. The experiment was carried out by changing the roll accerelation of the outer cylinder, and the moment acting on the inner cylinder was measured. Experimental results were discussed in the following three ways. At first the magnetic fluid was treated as a Newtonian fluid, and a small difference in the flow curves was found. Next the power law theory was applied in order to explain these differences. Finally the authors examined this flow problem using the micropolar theory, which gives the theoretical relation between the moment acting on the inner cylinder and the roll accerelation of the outer one. In this relation, a coefficient denotes the micropolar effect. The authors measured this value and showed the effect of the substructure on the fluid.

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Lateral sloshing of a magnetic fluid in a container

Tatsuo Sawada, Hiroshige Kikura, Syuntaro Shibata and Takahiko Tanahashi

Journal of Magnetism and Magnetic Materials (Elsevier)  122 ( 1-3 ) 424-427 1993.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

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The dynamic behavior of a magnetic fluid in a laterally oscillating rectangular container was experimentally studied. A vertical non-uniform magnetic field was applied to the container. The resonant frequency of the fluid-container system moved toward the high frequency region with the magnetic field intensity. An experiment was also carried out for a two-phase liquid of magnetic fluid and kerosene.

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Natural convection of a magnetic fluid in a cubic enclosure

Hiroshige Kikura, Tatsuo Sawada and Takahiko Tanahashi

Journal of Magnetism and Magnetic Materials (Elsevier)  122 ( 1-3 ) 315-318 1993.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

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Laminar natural convection heat transfer of a magnetic fluid in a cubic enclosure is examined experimentally. Wall-temperature distributions are visualized by thermosensitive liquid crystal sheets. The effect of the magnetic field on the transient temperature distributions, and the local and averaged Nusselt numbers are discussed.

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Structure of a starting vortex

Thomas Leweke and Tatsuo Sawada

Proceedings of the Sixth International Symposium on Flow Visualization, Flow Visualization VI    196-200 1992.10

Research paper (international conference proceedings), Joint Work

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The time-dependent flow structure inside a slender starting vortex, which was bounded in the axial direction either by two solid walls or by a wall and a free surface, has been investigated experimentally in water. Particle traces and the dye-injection method were used for velocity measurements and flow visualizations. Numerical simulations were also carried out in order to identify several mechanisms responsible for the observed phenomena.

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Transportation of a magnetic fluid by rotating magnetic fields

Hiroshige Kikura, Tatsuo Sawada andTakahiko Tanahashi

Elsevier Studies in Applied Electromagnetics in Materials, Electromagnetics Forces and Applications (Elsevier)  1   103-106 1992.01

Research paper (international conference proceedings), Joint Work, Accepted

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The surface flow patterns of a magnetic fluid in a cylinder and annular cylinders under the rotating magnetic field were precisely examined. On the basis of these experimental results, a new transport system of a magnetic fluid using rotating magnetic field was proposed. When the rotating magnetic field was applied, the height difference of fluid columns was observed. The pressure head was influenced by the magnetic field intensity, its frequency, diameters of the spiral tube and core cylinder. Effects of these parameters were examined.

Some interesting behaviors of a magnetic fluid

Tatsuo Sawada, Hiroshige Kikura and Takahiko Tanahashi

Physiological Fluid Dynamics (Narosa Publishing House)  3   303-310 1991.12

Research paper (conference, symposium, etc.), Joint Work

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Magnetic fluids have been studied in the various fields for over two decades. In the present paper, following three different experimental studies were carried out in order to present interesting characteristics of a magnetic fluid: lateral fluid--sloshing in a container, natural convection of a magnetic fluid between two coaxial annuli and rotational flow driven by a rotating magnetic field.

Lateral sloshing of a magnetic fluid under a vertical non-uniform magnetic field

Tatsuo Sawada, Hiroshige Kikura and Takahiko Tanahashi

Conference Proceedings, 8th International Congress of Cybernetics and Systems I   292-298 1991.12

Research paper (conference, symposium, etc.), Joint Work, Accepted

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Dynamic behaviors of a magnetic fluid in three different containers were experimentally studied. Experiments were carried out for rectangular, cylindrical and spherical containers, respectively. These containers were laterally oscillated. The vertical non-uniform magnetic field was applied by permanent magnets which were fitted underneath the container. Test liquid was a magnetic fluid with 33\% weight concentration of fine magnetite particles in a water carrier. It was found that harmonic wave motion, swirling waves and flow pattern of surface waves were influenced by the magnetic fields. The resonant frequency of the fluid-container system moved toward high frequency region with the magnetic field intensity. This behavior was also examined by the linear approximate theory. Theoretical results were qualitatively in good agreement with experimental results.

Numerical Analysis of Nonlinear Water Waves Using Arbitrary Lagrangian-Eulerian Finite Element Method

Hiroshige Kikura, Tooru Takeguchi, Tatsuo Sawada and Takahiko Tanahashi

Transactions of the Japan Society of Mechanical Engineers, Ser.B (Japan Society of Mechanical Engineers)  57 ( 540 ) 2632-2639 1991.08

Research paper (scientific journal), Joint Work, Accepted

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Since free surface flows are seen in nature phenomena and artificial systems, the analysis for these flows has been more important in mechanical engineering. However, theoretical analyses are almost impossible because the boundary conditions are nonlinear equations in analyzing the free surface flows. Thus, numerical analyses are needed. Finite element method (FEM) which can be used for unstructured grid can easily treat boundary conditions. Thus, FEM is used in many technological fields. In this thesis, free surface flow problems were analyzed using the finite element method. In solving these problems, an arbitrary Lagrangian-Eulerian (ALE) kinematical description of the fluid domain was adopted, in which the nodal point can be displaced independently of the fluid motion. The ALE method was introduced into the Generalized Simplified Marker and Cell (GSMAC) method. Damping out the alternating errors was examined in this scheme.

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New transport system of a magnetic fluid by rotating magnetic fields

Hiroshige Kikura, Tatsuo Sawada andTakahiko Tanahashi

ASME FED-Vol.115, Liquid Metal Flows (ASME)     31-35 1991.06

Research paper (international conference proceedings), Joint Work, Accepted

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The magnetic fluid motion in a rotating magnetic field was examined at first. Influences of the magnetic field intensity, its frequency and the radius ratio of the concentric cylinders on flow patterns were investigated experimentally. According to these results, a new transport system of a magnetic fluid was presented. It consisted of the spiral tube wound around a circular cylinder. When the rotating magnetic field was applied, the height difference of fluid columns was observed, which corresponded to the pressure head between the entrance and exit of the tube. The pressure head was influenced by the magnetic field intensity, its frequency and diameter of the spiral tube. Effects of these parameters were discussed.

Natural convection of a magnetic fluid in concentric horizontal annuli

Tatsuo Sawada, Hiroshige Kikura, Atsushi Saito and Takahiko Tanahashi

Proceedings of the Second World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics    1433-1440 1991.06

Research paper (international conference proceedings), Joint Work

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Natural convection of a magnetic fluid in concentric annuli was investigated experimentally. A thermosensitive liquid crystal was utilized for temperature visualization instead of flow visualization. When there was no magnetic field, developments of ordinary natural convection were observed. When a magnetic field was applied in the same direction of the gravity, wall-temperature distribution was observed as if an apparent gravity increased. But the clear influence of the magnetic field was not found. If a magnetic field was applied in the opposite direction of the gravity, the reverse natural convection was observed. Consequently, even if the intensity of the applied magnetic field was small, it played an important role in natural convection and heat transfer of a magnetic fluid. It was recognized that natural convection of a magnetic fluid could be controlled by the applied magnetic field.

磁性流体スロッシングにおける液面挙動と周波数応答

木倉宏成，澤田達男，棚橋隆彦

Transactions of the Japan Society of Mechanical Engineers, Ser.B (Japan Society of Mechanical Engineers)  57 ( 537 ) 1629-1634 1991.05

Research paper (scientific journal), Joint Work, Accepted

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矩形，円筒，球形容器に内に満たされた磁性流体のスロッシング現象に及ぼす磁場の影響を調べた。その結果，印加磁場の増加に伴って共振振動数が高周波数側に移行し，液面動揺も抑えられる事が明らかとなった。また，実験結果は理論解析結果ともよく一致し，理論解析の妥当性が確認できた。

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Numerical simulation of unsteady incompressible viscous flows by improved GSMAC-FEM

Yasumasa Kato, Toshihiro Sato, Tatsuo Sawada and Takahiko Tanahashi

Lecture Notes in Physics (Springer)  371   209-210 1990.12

Research paper (international conference proceedings), Joint Work,  ISSN  0075-8450

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A new FEM scheme using simultaneous relaxation of velocity and Bernoulli function is presented for unsteady incompressible viscous flow. This is an improved version of the GSMAC(Generalized Simplified Marker and Cell) FEM. To verify the scheme, transient 2-D Poiseuille flow and 3-D flow in a lid-driven cubic cavity are numerically calculated.

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Natural convection of a magnetic fluid under magnetic fields

Hiroshige Kikura, Tatsuo Sawada, Takahiko Tanahashi and Atsushi Saito

Proceedings of the Second KSME-JSME Fluids Engineering Conference (KSME, JSME)  2   128-133 1990.10

Research paper (conference, symposium, etc.), Joint Work

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容器内の磁性流体自然対流が印加磁場によって制御できる事を明らかにし、その熱伝達特性を調べた。

Propagation of surface waves of magnetic fluids in traveling magnetic fields

Hiroshige Kikura, Tatsuo Sawada andTakahiko Tanahashi

Journal of Magnetism and Magnetic Materials (Elsevier)  85 ( 1-3 ) 167-170 1990.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

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Propagation of waves on the free surface of magnetic fluid is experimentally investigated. It is found that the surface velocity of the magnetic fluid depends on the intensity and frequency of traveling magnetic fields, and depth of the channel contained with the magnetic fluid. Theoretical investigation is also carried out in order to clarify the phenomena.

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GSMAC-FEM for incompressible viscous flow analysis (A modified GSMAC method)

Hideki Kawai, Yasumasa Katoh, Tatsuo Sawada and Takahiko Tanahashi

JSME International Journal, Ser.II (JSME)  33 ( 1 ) 17-25 1990.02

Research paper (scientific journal), Joint Work, Accepted

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The rotational form of the Navier-Stokes equations in which velocity and the Bernoulli function are variables is used in the GSMAC method. Velocity components and Bernoulli function are interpolated as a linear function and a constant function, respectively. This interpolation is simple and convenient for creating the mesh system. However, the approximation which is mentioned above makes it difficult to analyze inlet-outlet flows including the Neumann boundary conditions. The present paper shows a new modified GSMAC method which is applicable to high Reynolds flows with Neumann boundary condition (especially the pressure boundary). The modified scheme consists of an algorithm which satisfies the continuity equation much better than the previous GSMAC method.

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Flow of the entrance region in a porous pipe : flow with a change of radial wall velocity

Hideki Kawai, Tatsuo Sawada, Takahiko Tanahashi

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  55 ( 515 ) 1829-1835 1989.07

Research paper (scientific journal), Joint Work, Accepted

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A theoretical solution of a pulsatile flow in the entrance region of a porous pipe was derived by Oseen's approximation reported in the previous paper when the radial wall velocity was constant along the pipe axis. According to Hornbeck's investigation, radial wall velocity alters due to the difference between the inner and outer pressure of a porous pipe. In the present paper, we dealt with a pulsatile flow whose radial wall velocity varies exponentially along the pipe axis. Dynamic characteristics such as velocity, and pressure coefficient are precisely discussed on the boundary conditions for pulsatile injection and suction from the pipe wall.

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GSMAC-FEM for incompressible viscous flow analysis : A modified gsmac method

Hideki Kawai, Tatsuo Sawada, Takahiko Tanahashi

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  54 ( 507 ) 3118-3125 1988.11

Research paper (scientific journal), Joint Work, Accepted

　View Summary

The GSMAC-FEM (Generalized Simplified Marker and Cell FEM) which is an extension of the SMAC-FDM is a stable and fast scheme for the incompressible viscous flow. The rotation form of the Navier-Stokes equation in which velocity and Bernoulli function are interpolated as a linear function and a constant function. This interpolation is simple and convenient in making the mesh system. On the contrary, the approximation which is mentioned above makes it difficult to analyze inlet-exit flow including the Neumann's boundary conditions. The present paper shows a modified GSMAC method which is available for high Reynolds flows with Neumann's boundary conditions (especially the pressure boundary).The modified scheme consists of an algorithm which satisfies the continuity equation much more than the previous GSMAC method.

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Numerical simulation of a blood flow in a stenosed tube

Hideki Kawai, Tatsuo Sawada and Takahiko Tanahashi

Role of Blood Flow in Atherogenesis (Springer)     131-137 1988.10

Research paper (international conference proceedings), Joint Work, Accepted

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A new finite element technique which is based on the multiplier method is presented to analyze incompressible flow problems. We apply this method to the flow analysis in a stenosed tube which is modeled by a cosine curve. Calculations are carried out for the flow whose Reynolds number is less than 1000. These results are compared with those obtained by a finite difference method. Separation and reattachment points agree with experimental results.

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Propagation of waves on the surface of a magnetic fluid by a traveling magnetic field

Tatsuo Sawada, Hiroshige Kikura and Takahiko Tanahashi

Proceedings of the 6th International Congress on Experimental Mechanics 1   264-269 1988.06

Research paper (international conference proceedings), Joint Work

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Propagation of waves on the surface of a magnetic fluid are investigated experimentally. It is found that the surface velocity of a magnetic fluid depends on intensity of a magnetic fie1d, frequency of a traveling magnetic field and depth of a magnetic fluid. Influences of these parameters on the propagation of waves are precisely examined. The surface velocity is proportional to intensity of a magnetic field. There exists the most suitable condition which gives the maximum surface velocity. This condition is closely connected with the frequency of a traveling magnetic field and the depth of a magnetic fluid. Theoretical investigation is also carried out in order to clarify the present phenomenon.

Numerical analysis of a flow in a stenosed tube

Hideki Kawai, Tatsuo Sawada and Takahiko Tanahashi

Physiological Fluid Dynamics 2   98-103 1987.08

Research paper (conference, symposium, etc.), Joint Work

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狭窄管内流れの数値解析を行い，狭窄の度合いによって，流線，等渦度線，狭窄部に作用するせん断応力がどのように変化するかを明らかにした。

Two-dimensional flow of magnetic fluid between two parallel plates

Tatsuo Sawada, Takahiko Tanahashi and Tsuneyo Ando

Journal of Magnetism and Magnetic Materials (Elsevier)  65 ( 2-3 ) 327-329 1987.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0304-8853

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Two-dimensional flows of magnetic fluid between two parallel plates in the transverse and longitudinal magnetic fields are investigated experimentally. The increasing rate of resistance coefficient is obtained and discussed with respect to the magnetic field length and Reynolds number.

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Unsteady forces on a body Immersed in a viscous fluid (3rd report: for an inclined thin elliptic cylinder)

Takahiko Tanahashi, Tatsuo Sawada, Eriya Kanai, Akira Chino and Tsuneyo Ando

Bulletin of JSME (JSME)  29 ( 257 ) 3717-3724 1986.11

Research paper (scientific journal), Joint Work, Accepted

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This paper considered a flow normal to an infinite thin elliptic cylinder which is uniformly accelerated from rest in a direction perpendicular to its generating lines in a viscous fluid. The Dufort-Frankel method for vorticity transport equation is used for the numerical simulation of viscous incompressible flows, and a new finite Fourier transform method is introduced in order to handle the stream function equation for accurate and efficient calculation. A major part of the present paper is devoted to physical properties of the flow during the early stages of wake developement behind an obstacle, for a Reynolds number of 98.11. A computer-aided flow visualization technique is used to demonstrate the main features of the hydrodynamic field for the flow. The rest of this paper demonstrates the important unsteady forces such as time-dependent drag, lift and moment acting on a body immersed in a viscous fluid, and presents specific numerical results for various transitions.

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Two-dimensional pneumatic wave propagation in pipes due to a step pressure input

Tatsuo Sawada, Takahiko Tanahashi and Tsuneyo Ando

Proceedings of the 5th International Conference on Pressure Surges    85-94 1986.09

Research paper (international conference proceedings), Joint Work, Accepted

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二次元流路内の圧力伝播の様子を特性曲線法を用いて数値解析を行い，速度分布，圧力分布の様子を明らかにした。

Dynamic characteristics of pneumatic transmission lines

Eriya Kanai, Tatsuo Sawada, Takahiko Tanahashi and Tsuneyo Ando

Fluid Control and Measurement 1   123-128 1986.08

Research paper (international conference proceedings), Joint Work, Accepted

　View Summary

空気菅路内に圧力波が入射された場合の圧力波動のステップ応答について実験と理論解析を実施し，その特性を詳細に調べた。

A new finite element method for solving the unsteady Navier-Stokes equation

Eriya Kanai, Tatsuo Sawada, Takahiko Tanahashi and Tsuneyo Ando

Computational Mechanics '86, Proceedings of International Conference on Computational Mechanics 2   Ⅶ/97-Ⅶ102 1986.05

Research paper (international conference proceedings), Joint Work

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ナビエ・ストークス方程式を解くための新しい有限要素法を提案し，その有効性について報告した。

Unsteady forces on an inclined thin elliptic cylinder

Tatsuo Sawada, Takahiko Tanahashi, Eriya Kanai and Tsuneyo Ando

Computational Mechanics '86, Proceedings of International Conference on Computational Mechanics 2   Ⅶ/35-Ⅶ40 1986.05

Research paper (international conference proceedings), Joint Work

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扁平な傾斜だ円柱に作用する非定常流体力を差分法による解析によって求めた。レイノルズ数によって，それらがどのように変化するかを調べた。

Unsteady forces on a body immersed in a viscous fluid : 3rd Report, for an inclined thin elliptic cylinder

Takahiko Tanahashi, Tatsuo Sawada, Eriya Kanai, Akira Chino, Tsuneyo Ando

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  52 ( 475 ) 1197-1206 1986.03

Research paper (scientific journal), Joint Work, Accepted

　View Summary

The flow normal to an infinite thin elliptic cylinder which is uniformly accelerated from rest in a direction perpendicular to its generating lines in a viscous fluid is considered. The Dufort-Frankel method for the vorticity transport equation is used for the numerical simulation of viscous incompressible flows, and a new finite Fourier transform method is introduced in order to handle the stream function equation for accurate and efficient calculation. A major part of the present paper is devoted to physical properties of the flow for the early stages of development of the wake behind the obstacle. A computer-aided flow visualization method is used to demonstrate the main features of the hydrodynamic field for the flow. The rest of this paper demonstrates the important unsteady forces such as time-dependent drag, lift and moment acting on the body immersed in a viscous fluid, and presents specific numerical results for various transition.

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Distorted pressure histories due to the step responses in a linear tapered pipe (6th report, for arbitrary cross-sections)

Takahiko Tanahashi, Tatsuo Sawada, Kazuyuki Shizawa and Tsuneyo Ando

Bulletin of JSME (JSME)  29 ( 249 ) 795-801 1986.03

Research paper (scientific journal), Joint Work, Accepted

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This paper describes one such development. A new method of solving a one-dimensional wave equation in linear tapered compound pipes with arbitrary cross-sections has been devised. Results obtained by this theory are compared with experiments in pipes with square cross-sections. And we obtained the following conclusions: (1) Damping coefficients in an arbitrary cross-section are defined and are expressed analytically for some representative cross-sections. (2) The viscous solution of a wave equation obtained by Laplace transform explains well distorted pressure histories in a linear tapered pipe with an arbitrary cross-section. (3) Pressure waves in a square cross-section include higher modes of frequency and damp more rapidly than those in a circular cross-section. but fundamental characteristics as waves are independent of the cross-section of the pipe except for the small aspect ratio.

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Oscillatory flow of a micropolar fluid in a circular tube

Tatsuo Sawada, Takahiko Tanahashi and Tsuneyo Ando

Physiological Fluid Dynamics 1   91-96 1985.12

Research paper (conference, symposium, etc.), Joint Work

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円管内の極性流体の振動流を解析し，血液流の実験結果との比較検討を行った。

Unsteady forces acting on a body immersed in viscous fluids (2nd report, uniformly accelerated flat plate, elliptic cylinder and circular cylinder)

Takahiko Tanahashi, Tatsuo Sawada, Eriya Kanai, Akira Chino and Tsuneyo Ando

Bulletin of JSME (JSME)  28 ( 242 ) 1634-1641 1985.08

Research paper (scientific journal), Joint Work, Accepted

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The initial stage of flows due to uniformly accelerated flat plate, elliptic and circular cylinders from rest in incompressible viscous fluids are numerically studied by the finite difference method. The time dependence of stream lines and equi-vorticity lines are shown in flow patterns. The Dufort-Frankel technique is used for solving the vorticity transport equation and the finite Fourier tranform for solving the stream function, which is applied to the analysis of a block tridiagonal matrix equation. The main conclusions are as follows; (1) The Fourier series method is more than ten times faster than the SOR method. (2) Numerical experiments here are in very good agreement with real experiments on a flat plate and a circular cylinder. (3) The length of vortex pairs behind a uniformly accelerated elliptic cylinder at the angle of attack 90° is obtained as a resultant of numerical experiments. (4) The growing process of the secondary vortices behind a circular cylinder is revealed at Reynolds number 731.

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Distorted pressure histories due to the step responses in a linear taperd pipe : 6th Report, for arbitrary cross-sections

Takahiko Tanahashi, Tatsuo Sawada, Kazuyuki Shizawa, Tsuneyo Ando

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  51 ( 467 ) 2313-2320 1985.07

Research paper (scientific journal), Joint Work, Accepted

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Although much progress has already been made in solving problems in step responses of pressure in a linear tapered pipe, new developments are still needed before the two dimensional wave equation can be solved routinely. This paper describes one such development. A new method of solving one dimensional wave equation in linear tapered compound pipes with arbitrary cross-sections has been devised. Results which are obtained from this theory are compared with experiments in pipes with square cross-sections. And we obtained the following conclusions: (1) Damping coefficients in an arbitrary cross-section are defined and are expressed analytically for some representative cross-sections. (2) The viscous solution of wave equation obtained by Laplace transformation explains well distorted pressure histories in a linear tapered pipe with an arbitrary cross-section. (3) Pressure waves in a square cross-section include higher modes of frequency and damp rapidly more than ones in a circular cross-section. But fundamental characteristics as waves are independent of the cross-section of the pipe except for the small aspect ratio.

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Unsteady forces on a boody immersed in viscous fluids : 2nd Report, uniformly accelerated flat plate, elliptic and circular cylinders

Takahiko Tanahashi, Tatsuo Sawada, Eriya Kanai, Akira Chino, Tsuneyo Ando

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  50 ( 460 ) 3142-3151 1984.12

Research paper (scientific journal), Joint Work, Accepted

　View Summary

The early stage of the flows due to uniformly accelerated flat plate, elliptic and circular cylinders from rest in incompressible viscous fluids are numerically studied by the finite difference method. The time dependence of streamlines and equi-vorticity lines are shown in the flow patterns. The Dufort-Frankel technique is used for solving the vorticity transport equation and the finite Fourier transport equation and the finite Fourier transform for solving the stream function, which is applied to the analysis of a block tridiagonal matrix equation. The main conclusions are as follows ; (1) The Fourier series method is more than ten times faster than the SOR method. (2) Numerical experiments obtained here have very good agreements with real experiments for flat plates and circular cylinders. (3) The length of vortex pairs behind an uniformly accelerated elliptic cylinder at the attack angle 90° is obtained as a resultant of numerical experiments. (4) The growing process of the secondary vortexes behind a circular cylinder is revealed at Reynolds number 731.

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Unsteady forces on a body immersed in viscous fluids (1st report: for a uniformly accelerated elliptic cylinder)

Takahiko Tanahashi, Tatsuo Sawada, Akira Chino, Shinji Kawamoto and Tsuneyo Ando

Bulletin of JSME (JSME)  27 ( 230 ) 1598-1606 1984.08

Research paper (scientific journal), Joint Work, Accepted

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A new numerical method for obtaining the forces on a body immersed in viscous fluids is derived for a uniformly accelerated elliptic cylinder from rest. In an analytical study, Fourier series expansion and boundary layer variable expansion are used because of good convergence and accuracy at high Reynolds numbers. An application of discrete Fourier transform to a block tridiagonal matrix leads to a high speed calculation over ten times as fast as the SOR method. From this analysis, the coefficients of drag, lift and moment exerted on a unit spanlength are obtained, and they consist of two components due to pressure and viscous force. Distribution of vorticities on the surface, which is important for the characteristics of heat conduction, is reveal ed in detail. Furthermore, the authors confirm that the separation time shown by Blasius at the trailing edge has a larger error when the eccentricity of the elliptic cylinder goes to unity.

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Response of magnetic fluids in annular pipes under the influence of external magnetic fields

Takahiko Tanahashi, Tatsuo Sawada, Kazuyuki Shizawa and Tsuneyo Ando

Bulletin of JSME (JSME)  27 ( 229 ) 1431-1437 1984.07

Research paper (scientific journal), Joint Work, Accepted

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A phenomenological treatment is given for steady magnetic fluid flows in annular pipes in the presence of uniform external magnetic fields. It is found that the apparent viscosity of a dilute colloidal suspension of ferromagnetic particles is a marked function of both the magnitude and direction of an externally applied magnetic field. The experimental fact shown by McTague(1969) that the additional viscosity is greater by a factor of 2 for the field parallel to the flow than for the field perpendicular to the flow is theoretically explained. Analytical expressions are derived for the distributions of velocities and angular velocities of the magnetic fluid in annular pipes under the influence of the external field. The induced magnetization calculated here to the first order is skewsymmetric with respect to the plane through the center line of the pipe and perpendicular to the applied magnetic field.

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The forces on a body in an unsteady viscous fluid : 1st Report, for an uniformly accelerated elliptic cylinder

Takahiko Tanahashi, Akira Chino, Shinji Kawamoto, Tatsuo Sawada, Tsuneyo Ando

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  49 ( 448 ) 2677-2684 1983.12

Research paper (scientific journal), Joint Work, Accepted

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だ円柱が突然加速運動を開始した場合のだ円柱まわりの流れ場を差分法によって数値解析し，だ円柱の抗力係数，揚力係数が時間経過と共にどのように変化するかを調べた。

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Response of ferrofluids in annular pipes under the influence of external magnetic fields

Takahiko Tanahashi, Tatsuo Sawada, Kazuyuki Shizawa, Tsuneyo Ando

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  49 ( 447 ) 2513-2521 1983.11

Research paper (scientific journal), Joint Work, Accepted

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A phenomenological treatment is given for the steady ferrofluid flows in annular pipes in the presence of uniform external magnetic fields. It is found that the apparent viscosity of a dilute colloidal suspension of ferromagnetic particles is a marked function of both the magnitude and direction of an externally applied magnetic field. The experimental fact shown by McTague (1969) that the additional viscosity is greater by a factor of 2 for the field parallel to the flow than with it perpendicular is theoretically explained. Analytical expressions of the distributions of velocity and angular velocity of the ferrofluid in annular pipes are derived under the influence of the external field. The induced magnetization calculated here to first order is skewsymmetric with respect to the plane through the center line of the pipe and perpendicular to the applied magnetic field.

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Stokesian flow of a micropolar fluid past a sphere

Tatsuo Sawada, Toshihiro Kamata, Takahiko Tanahashi and Tsuneyo Ando

Keio Science and Technology Reports (Keio University)  36 ( 4 ) 33-47 1983.09

Research paper (bulletin of university, research institution), Joint Work, Accepted

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極性流体の球まわりのStokes流を理論解析した。各種パラメータが流線，等渦度線に及ぼす影響を調べた。

A note on the analytical treatment in ferrohydrodynamics

Takahiko Tanahashi, Tatsuo Sawada, Tsuneyo Ando, Motoichi Iga and Hiroyuki Torii

Bulletin of JSME (JSME)  26 ( 219 ) 1509-1517 1983.09

Research paper (scientific journal), Joint Work, Accepted

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A new complete set of basic equations for magnetic suspensions is derived on the theory of micropolar fluids developed by Eringen and a solution to these basic equations is obtained analytically for a steady motion of magnetic suspensions in a circular pipe which is placed in a homogeneous magnetic field parallel to the flow direction. A phenomenological treatment is given for the specification of material constants of a micropolar fluid, which are vortex viscosity and spin viscosity. In order to clarify the dynamical flow characteristics in the presence of a magnetic field, six dimensionless parameters to show the magnetic effect, polar effect, wall surface effect and so on are introduced into the solution for the rotational Peclet number. Some discussions are presented on velocity profiles, distribution of microrotations and distribution of vorticities. In particular, the suspension is non-Newtonian even if a magnetic field does not exist.

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A note on the analytical treatment in ferrohydrodynamics

Takahiko Tanahashi, Tatsuo Sawada, Tsuneyo Ando, Motoichi Iga and Hiroyuki Torii

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  49 ( 437 ) 53-61 1983.01

Research paper (scientific journal), Joint Work, Accepted

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磁性流体の構成方程式を新たに提案し，それを円管内の流れ場解析に用いた。そして，従来明確で無かった流れ場の様子を明らかにした。

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Distorted pressure histories due to the step responses in a linear tapered pipe (5th report, case of a tank being installed at the end)

Takahiko Tanahashi, Yutaka Yamashita, Tatsuo Sawada and Tsuneyo Ando

Bulletin of JSME (JSME)  25 ( 208 ) 1521-1528 1982.10

Research paper (scientific journal), Joint Work, Accepted

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Distorted pressure histories in a linear tapered tube equipped with a tank at the end are experimentally investigated by the step pressure input. And also this problem is theoretically solved by two methods, i.e., eigenfunction expansion and asymptotic expansion. The peak pressure in the tube can be controlled by the capacity of the tank. Large capacity leads to an open end situation. The height of the pressure wave is proportional to the inverse of the tube radius. A one dimensional wave equation including the viscous term in the equation of motion and the effect of the variable cross section is simplified by special transformation, and the simplified equation is solved by the method of the Laplace transform. The resultant analytical solution has a clearer representation than Schuder-Binder's solution.

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Oscillatory flow of a micropolar fluid as a model for blood flow

Tatsuo Sawada, Takahiko Tanahashi and Tsuneyo Ando

Keio Science and Technology Reports (Keio University)  35 ( 6 ) 105-121 1982.07

Research paper (bulletin of university, research institution), Joint Work, Accepted

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血液流のモデルとして極性流体の円管内流れを取り上げ，血液の流動解析への適用性について検討し，ヘマトクリットを変化させた場合の実験結果との比較検討を行った。

Flow of the entrance region in a porous pipe (3rd report: transient flow)

Takahiko Tanahashi, Hideki Kawai, JunMasuzawa, Tatsuo Sawada and Tsuneyo Ando

Bulletin of JSME (JSME)  25 ( 205 ) 1070-1078 1982.07

Research paper (scientific journal), Joint Work, Accepted

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This study deals with a transient laminar flow, which is started from rest, in the entrance region of a porous pipe. This flow analysis is applied to transpiration cooling systems and research equipment for production of tidal current. In this report, the problem is analyzed by a modified momentum integral method using the integral form of the equations of continuity, momentum and energy. The following conclusions were obtained ; (1) Dynamic distributions of velocity profiles, wall frictions and pressures are obtained numerically. (2) The relation between the flow rate of injection or suction and inlet length of the entrance region is made clear. (3) Each dynamic state in the pipe is found with changeable inlet velocities and with variable sections or injections. (4) It is confirmed that the modified momentum integral method is valid for the slip velocity on the porous wall which makes the inlet length short.

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極性流体の二重円管内の軸方向定常流れ

澤田達男，棚橋隆彦，安藤常世

日本機械学会論文集(Ｂ編) (日本機械学会)  48 ( 427 ) 576-580 1982.03

Research paper (scientific journal), Joint Work, Accepted

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二重円管内の極性流体の軸方向定常流れを理論解析し，その流動特性を明らかにした。

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Distorted pressure histories due to the step responses in a linear tapered pipe (5th Report, case of a tank being installed at the end)

Takahiko Tanahashi, Yutaka Yamashita, Tatsuo Sawada and Tsuneyo Ando

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  48 ( 426 ) 220-228 1982.02

Research paper (scientific journal), Joint Work, Accepted

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末端に圧力タンクが設置された直線テーパ管内の圧力波動の伝播の様子を実験を行って明らかにし，理論解析結果と比較検討し，理論解析の有効性を明らかにした。

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Oscillatory flow of a fluid with couple stress

Tatsuo Sawada, Takahiko Tanahashi and Tsuneyo Ando

Keio Science and Technology Reports (Keio University)  34 ( 4 ) 65-82 1981.12

Research paper (bulletin of university, research institution), Joint Work, Accepted

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偶応力を持つ流体として極性流体を取り上げ，その管内振動流を解析し，偶応力の流れ場に及ぼす影響を調べた。

Flow of the entrance region in a porous pipe (3rd Report: transient flow)

Takahiko Tanahashi, Hideki Kawai, JunMasuzawa, Tatsuo Sawada and Tsuneyo Ando

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  47 ( 423 ) 2131-2138 1981.11

Research paper (scientific journal), Joint Work, Accepted

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多孔質円管内の助走区間領域における過渡流れを理論的に調べ，しみ出し・しみ込み速度が速度分布の発達過程に及ぼす影響を明らかにした。

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Fundamental steady flow of polar fluids

Tatsuo Sawada and Takahiko Tanahashi

Bulletin of JSME (JSME)  24 ( 196 ) 1778-1786 1981.10

Research paper (scientific journal), Joint Work, Accepted

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A few fundamental steady flows of polar fluid, i.e., flow in a circular tube, flow between two parallel plates and flow between two coaxial cylinders are analyzed with the help of the theory of Eringen. Couple stress and spin angular momentum are considered in this approach. The exact solutions for velocity, micro-rotation, vorticity and shearing stress are obtained mathematically. These solutions are characterized by two parameters, i.e., the ratio of viscosities ε and the size effect parameter λ which do not appear in a Newtonian fluid. ε is the ratio of vortex visoosity to shear viscosity. λ means the size relation between the corpuscle and the characteristic length. The solutions are compared with those of Newtonian fluid and it is investigated how they vary with ε and λ. Apparent viscosity is determined for each flow. Material constants of polar fluid can be decided from these apparent viscosities.

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Fundamental steady flow of polar fluids

Tatsuo Sawada and Takahiko Tanahashi

Transactions of the Japan Society of Mechanical Engineers Series B (Japan Society of Mechanical Engineers)  47 ( 414 ) 287-296 1981.02

Research paper (scientific journal), Joint Work, Accepted

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極性流体の各種の定常流れを理論解析し，寸法効果パラメータ，極性効果パラメータの諸量が流れ場に及ぼす影響を調べた。

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円管内における極性流体の流れの解析(第２報，壁面上でスピンがある場合の脈動流)

棚橋隆彦，澤田達男，安藤常世

日本機械学会論文集(Ｂ編) (日本機械学会)  46 ( 402 ) 272-281 1980.02

Research paper (scientific journal), Joint Work, Accepted

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円管内の極性流体の振動流を壁面でスピンがある場合の境界条件に基づいて理論解析を行い，速度分布と角速度分布を求めた。そして，振動特性に及ぼす諸パラメータの影響を調べた。

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円管内における極性流体の流れの解析(第１報，壁面上でスピンがない場合の脈動流)

棚橋隆彦，安藤常世，澤田達男

日本機械学会論文集(Ｂ編) (日本機械学会)  45 ( 389 ) 20-27 1979.01

Research paper (scientific journal), Joint Work, Accepted

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円管内の極性流体の振動流を壁面でスピンがない場合の境界条件に基づいて理論解析を行い，速度分布と角速度分布に及ぼす寸法効果パラメータや極性効果パラメータの影響を調べた。

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