Shear Layer Studies — Past, Present, Future

Summary

Assuming that the Navier Stokes equations can be taken as accurate, it is strictly correct to say that fluid dynamics is just a computing problem! However, the first laminar boundary layer calculations were carried out by Blasius only 75 years ago, full turbulent-flow simulations have only recently been achieved in highly restricted conditions, and some people doubt whether transition from laminar to turbulent flow can ever be treated as a well posed mathematical problem. Our inability to solve the time dependent Navier Stokes equations in cases of engineering interest has led to (1) the flourishing branch of science called “experimental fluid dynamics” (2) equally flourishing theoretical work on simplifications of the Navier Stokes equations, of which the foremost is based on Prandtl’s concept of the thin shear layer. This paper is a look back down the road along which shear layer calculations have marched, and a forward look to see where we go from here.