Affiliations: Nuclear Engineering Research Laboratory, The
University of Tokyo, Tokai-mura, Ibaraki, 319-1188, Japan.
Abstract: The visualization study on the microstructure of the
Electro-Rheological (ER) fluid was carried out. The dense particle motion was
difficult to visualize because of the severe light scattering by the particle
itself. In this study, the laser light sheet was illuminated to visualize the
dense particle condition, 10 wt%. As the ER fluid, the cholesterol particles
(~20 mm) were dispersed into the silicone oil (10 cS). The humidity of particle
was controlled to be 4%. The particle density was set to be 10 wt%. Under this
condition, individual particle could not be distinguished. However, the
particle cluster motion could be clearly visualized. With the electrical field,
the chains of the particles were formed. The ER fluid with the chain was
recorded onto the video camera. With higher electrical field, the layer of the
particle was formed at the top and bottom electrode. The layer caused the
decrease of the fluid channel width, resulting in the resistance to be
increased. The effects of electrical field on the layer formation were
experimentally investigated. The Mason number, which is the ratio of shear
force to electrical force, was found to be the key parameter of the layer
formation.