Published papers

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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。

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.

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。

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.

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.

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.

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.

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.

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.