WALL SLIP CORRECTIONS FOR COUETTE AND PARALLEL DISK VISCOMETERS

Often for slurries, gels, emulsions, and foams inhomogeneous fluid properties at solid boundaries create apparent wall slip. The reduced fluid viscosity at the boundary creates a thin layer of fluid having a large velocity gradient that can be treated as a slipping layer. In measurements of fluid viscosity it is necessary to correct for wall slip to determine the true deformation experienced by the bulk of the sample and the true viscosity. The classic earlier techniques for capillaries and Couette geometries were first presented by Mooney. We present a new analysis of the Couette geometry that requires only two measurements rather than the three used by Mooney. We also present a new analysis for flow between rotating parallel disks. The parallel disk geometry has several experimental advantages for measuring fluid viscosities in the presence of wall slip. The analysis of experimental data on a clay suspension and oil-in-water emulsion are presented to demonstrate these new techniques.