Date of Award

Spring 2003

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering - (M.S.)

Department

Mechanical Engineering

First Advisor

Pushpendra Singh

Second Advisor

N. Aubry

Third Advisor

Anthony D. Rosato

Abstract

A numerical method based on the distributed Lagrange Multiplier method is developed for direct simulation of electrorheological (ER) suspensions subjected to pressure driven flows and spatially non-uniform electric fields. The flow inside particle boundaries is constrained to be rigid body motion by the distributed Lagrange multiplier method and the point-dipole approximation is used to model the electrostatic forces acting on the polarized particles. Simulations show that the particles move to the regions of high electric field when the value of β, the Clausius-Mossotti factor is positive and they move to the regions of low electric field when the value of β is negative. Also, dielectrophoretic force can be used for separating particles with different β values.

Using the simulation method the evolution of the microstructure under the influence of electrostatic forces (particle-particle interaction force and dielectrophoretic force) and hydrodynamic forces is analyzed. The different microstructures formed are explained on the basis of non-dimensional parameters that determine the relative strength of the various forces. Simulations show that even when the particle-particle interaction force, dielectrophoretic force and hydrodynamic force coexists, the parameters can be judiciously manipulated so that either the yield stress and viscosity of the ER fluid increases or the particles get collected in the regions of low or high electric fields.

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