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Research Topics

1.Flow characteristics of high intelligent fluids
a) Microscopic behavior of ER (Electro-rheological) fluids is visualized using a high speed video camera and CCD camera, with a microscope viewing system, under the application of electric fields. The effect of electrical change and flow rate on the pressure drop is explained from the results of the flow visualization.
 b) The shear stresses of ER(Electro-rheological) fluids are measured by changing a shear rate , amplitude and frequency of electric fields using rotational viscometer. Unipolar sine-wave electric fields which are AC with DC bias and bipolar sine-wave electric fields without DC bias are used. Dependence of the shear stress on electrical excitation frequency and temperature is mainly investigated.

 Recently our research is focused to a liquid crystal.

2.Flow analysis in oil hydraulic control valves
Flow analysis in oil hydraulic control valve is conducted theoretically and experimentally. A vortex method, which is useful for solving turbulent flow and moving boundary problems, is developed. Two dimensional flow in a spool valve is solved using the vortex method when the valve is instantly opened and closed repeatedly. Three-dimensional axisymmetrical flow in a poppet valve for divergent flow is analyzed numerically using axisymmetric vortex method when a poppet is oscillating in the axial direction. Three-dimensional flow in a ball valve for divergent flow is analyzed numerically using the vortex method when the ball is oscillating. A deeper understanding of the behavior of the jet flow and fluid properties in oil hydraulic valve is realized by the present experimental and numerical flow visual examinations.

3.Flow-induced vibration

In order to reduce noise, the flow near the reed valve in a compressor for automotive air-conditioning is investigated using experimental and numerical flow visualization. The reed valve is improved to prevent vibration of the valve. Test facilities are designed to control flow rate, upstream pressure and the valve lift. Moreover, good results for the noise reduction are demonstrated by the noise measurement of the improved valve.

4.Cavitation in oil hydraulic components

Motion of bubbles is visualized in a hydraulic, vane-type power steering pump using a high speed video camera. Fluid properties are obtained from the vidsualized results using PIV(Particle-Image Velocimetry).

5.Flow simulation around bluff body using vortex method
Flow around a volley ball is simulated using 2-D vortex method with rotation of the ball. We plan to investigate the drag and the lift forces of the volley ball by changing the Reynolds number and the speed of the rotation. The results are compared with ones of the circular cylinder.

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