Elementary viscous flow

Abstract

Abstract Steady flow past a fixed aerofoil may seem at first to be wholly accounted for by inviscid flow theory. The streamline pattern seems right, and so does the velocity field. In particular, the fluid in contact with the aerofoil appears to slip along the boundary in just the manner predicted by inviscid theory. Yet close inspection reveals that there is in fact no such slip. Instead there is a very thin boundary layer, across which the flow velocity undergoes a smooth but rapid adjustment to precisely zero —corresponding to no slip —on the aerofoil itself (Fig. 2.1). In this boundary layer inviscid theory fails, and viscous effects are important, even though they are negligible in the main part of the flow.