Papers - Sawada, Tatsuo

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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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