Competition between Inertial Pressures and Normal Stresses in the Flow InducedAnisotropy of Solid Particles

摘要

In this paper we are putting forward the idea that flow induced anisotropy ofspherical particles finds its explanation in the flow induced turning couples on long bodies. The streamwise orientation of a settling or fluidized long body is unstable in a viscous liquid, and will always turn its broadside to the stream. An explanation for this can be found in the couples which are produced by high pressures at the stagnation points on the long body. Potential flow is probably a good approximation for viscous flow on the forward side of the body. If the pressures outside a thin boundary layer at the stagnation points were reversed, the long body would not put its broadside into the stream, but instead would put its broadside parallel to the stream, as is in fact the case in the settling of long cylinders in various viscoelastic liquids shown. In practice, the wakes which develop on the back side of bodies give rise to a drag.