Behavior of electrorheological fluids: A modeling and an experimental study

Electrorheological fluids are fluids that undergo a reversible change in flow properties. Many applications have been proposed for their usage, such as dampers, engine mounts and squeeze film dampers. Electrorheological Fluids are usually modeled as a Bingham fluid, which exhibits a yield stress then a sharp transition to Newtonian flow.; Expressions are developed for the damping coefficient of two types of viscous dampers that contain electrorheological (ER) fluids. The damping action in the first type occurs in flow between stationary parallel plates, the second type has annular flow between two stationary concentric cylinders. These expressions may facilitate the solution to mechanical systems problems using ER fluids and demonstrate the controllability of ER dampers.; Another topic discussed in this thesis is the analysis of annular flow between two concentric cylinders under an applied pressure gradient using the Dorier-Tichy model, which expresses the viscosity as a continuous function of the strain rate magnitude. For the special case of Bingham flow, the results compare favorably with the solution of Fredrickson and Bird. The effects of the three parameters in the new model on the velocity profile and flow rate are also shown.; The Bingham model parameters of a commercially available electrorheological (ER) fluid are determined using an axial flow concentric cylinder rheometer. Two methods are used to determine these parameters. One method is the Weissenberg method applied to thin annular slits, to obtain corrected stress-strain rate information. The other method involves directly curve fitting the velocity-pressure data to the axial flow rate equation of a Bingham fluid through concentric cylinders. The results obtained by these two methods differ by as much as 49.4 and 63.5 percent for the yield stress and viscosity, respectively.; It is observed for this ER-fluid that the yield stress increases according to a power law relationship with the applied electric field. The viscosity appears to decrease linearly with an increase in the applied electric field.; Finally, for a fluid with a yield stress behavior undergoing flow between an inclined and a sliding horizontal surface, the core geometry for the special cases of an upper core and lower core are investigated using the biviscous model.