SUSPENSION RHEOLOGY: A THEORY OF TIME-DEPENDENT PARTICLE MOTION IN NEWTONIAN FLUIDS AND AN EXPERIMENTAL STUDY OF COLLOIDS IN POLYMERIC MEDIA (FORCE CONDITION, SILICA SPHERES, SILICONE)
Abstract
The time-dependent motion of a particle in an incompressible Newtonian fluid in the limit of creeping flow is analyzed using linear operator framework. The general solution procedure is developed for two specific situations: (i) when an arbitrary time-dependent particle velocity is specified, and (ii) when an arbitrary time-dependent external force on the particle is specified. The farfield velocity can be fully three-dimensional and time-dependent. When the particle velocity is specified, the familiar Dirichlet boundary condition results. However, when a force on the particle is specified an integral boundary condition on the particle surface results, and the solution procedure required is quite different. Several examples of practical interest are solved for spherical particles. The traditional solutions due to Stokes, Boussinesq and Basset are recovered as special cases, and it is shown that the present solution framework is a very efficient method to determine particle trajectories when a time-dependent external force is applied to the particle. The effects of particle concentration, particle size, and continuous phase rheology on the viscometric properties of suspension of spherical, colloidal sized silica particles in polydimethylsiloxane fluids were examined. The data indicate that as the particle concentration is increased or particle size is decreased, (i) both the shear viscosity (eta) and primary normal stress coefficient (psi)(,1) increase, and (ii) the degree of shear thinning in both (eta) and (psi)(,1) increase. It is also observed that (psi)(,1) is more sensitive than (eta) to changes in either particle concentration or particle size. The effect of the details of the continuous phase rheology on the rheological properties of the suspension was studied by varying the primary normal stress coefficient of the continuous phase while holding the shear viscosity constant. The data indicate that a change in the rheology of the continuous phase affects the viscometric properties of the suspension significantly. Also, none of the available detailed hydrodynamic theories is adequate to describe all the experimental data.
Degree
Ph.D.
Subject Area
Chemical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.