Pressure characteristics of ER damper with different piston velocities

A basic experiment for the gap flow in a closed piston - cylinder system of ER fluid was carried out with regard to engineering application to dampers. The purpose of this study is to gain system characteristics and to elucidate flow behaviors of ER fluid in the piston-cylinder system; the model damper. Pressure, which is the system characteristic, was examined in the present study. The test fluid was a smectite ER fluid in silicone oil base of the 3wt% particle dispersion concentration. In the apparatus the piston moves in the vertical direction at a given speed. Theoretical formula of pressure difference is considered by the one-dimensional analysis of the ER flow in the gap of cylinder. It was shown that the response of the pressure was retarded with strong electric field. In comparison with the theoretical estimation and experimental value, the theoretical pressure difference was in good agreement with experimental data. For a sake of giving an insight to flow phenomena, visualization was also achieved using model Newtonian fluid in the piston-cylinder system, and shown that vorticity generated at the rear corner of the piston plays an important role for the pressure characteristic.