Diffusion and convection in viscous flow

Abstract

A survey is made of the way in which a variety of physical scalar and vector quantities are diffused, and convected out of fixed regions in moving fluids. In particular, viscous flow itself is viewed as the diffusion and convection of circulation which is generated at the boundaries of the fluid by the no-slip condition. The non-linearity of the problem arises from the fact that the convection field is in part self-generated by the diffused circulation. Ways of overcoming these difficulties are reviewed in the light of the above point of view. New kinematic interpretations are given for the equations governing axisymmetric viscous flow and these are used to determine the flow vector for ring circulation, angular momentum and other relevant physical quantities.