Published papers

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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。

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。

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。