Transient behavior of electrorheological fluids in shear flow

Self-similarity in electrorheological behavior

“…Contrary to the observation of coexistent fluid and solid regions in the plane of velocity and vorticity, recently many groups have observed stripe or lamella formation in a plane of the electric field and velocity below a critical Mason number. [23][24][25][26] All the cases that report stripe formation were shear rate controlled and in many cases the electric field was imposed after the deformation field was applied. Von Pfeil and coworker's 27,28 two fluid model, wherein imposition of an electric field was considered on the suspension undergoing shear, predicted the observed behavior very well.…”

“…two fluid model, wherein imposition of electric field was considered on the suspension undergoing shear, predicted the observed behavior very well. Von Pfeil and coworker's proposal suggested that below a critical Mason number, where stripe formation is observed, the response of shear stress is expected to be dependent on time (transient), while above critical mason number, where suspension shows uniform concentration profile, shear stress should remain constant 23. It should be noted that our experiments are stress controlled and the stress field is imposed after applying the electric field.…”

“…The surface normal of lamella or stripes was observed to be oriented in the vorticity direction. [23][24][25][26] Recently Von Pfeil et al 27,28 proposed a two fluid theory by developing a continuum model by accounting for the hydrodynamic and electrostatic contributions to net particle flux. The model predicted the formation of stripes in a sheared suspension below a critical Mason number.…”

“…Contrary to observation of coexisting solid -fluid region, many groups reported appearance of lamellar structure in steady shear flow. The surface normal of lamella or stripes was observed to be oriented in the vorticity direction [23][24][25][26]. Recently Von Pfeil et al27,28 proposed a two fluid theory by developing a continuum model by accountingfor hydrodynamic and electrostatic contributions to net particle flux.…”

Dielectric Analysis of Response Time in Electrorheological Fluids Developed for Medical Devices

“…ER active materials are generally polymers, ceramics, metals or composites such as cellulose, starch, titanium oxide, polyurethanes and polyanilines [1][2][3][4][5]. In the presence of an external AC electric field, typically a few kilovolts per millimeter, these ER active particles are polarized due to the dielectric difference between the suspended particles and the base fluid [6]. The field-induced dipoles on the particles cause them to align and form chains or fibrillated structures that bridge the electrode gap.…”