Shear-Thinning Effects in Creeping Flow about a Sphere

Abstract

Shear-thinning inelastic fluid behaviour is often described by the power law because of the simplicity of this model. Frequently also zero shear viscosity is difficult to measure and so a more realistic fluid model cannot be used. Despite the severe limitations of the power law in describing regions of a flow field where the shear rate approaches zero, it continues to be applied to the problem of creeping sphere motion. It has not yet been determined over what proportion of the sphere surface this fluid model breaks down. Presumably if the areas of the sphere surface about the front and rear stagnation points and the volume of fluid far from the sphere do not contribute significantly to the total drag of a sphere, then a power law description of the flow field may yield an acceptable result for the drag.