Papers - Sawada, Tatsuo

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

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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

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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

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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

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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

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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.