Turbulent Boundary Layer Development in the Presence of Small Isolated Two-Dimensional Surface Discontinuities

Abstract

Discontinuities in surfaces over which fluids flow can occur in a variety of situations. One of contemporary engineering significance is that which arises on aircraft wings, where the wing forms a junction with an auxiliary lifting surface. Such discontinuities are often two-dimensional and may well be small, lying within the logarithmic regions of the turbulent boundary layers in which they are immersed. In this paper such surface discontinuities are idealized into shapes whose drag coefficients, when they have been isolated from their surrounding surfaces, have been previously determined and tabulated. By making appropriate assumptions about the boundary layer characteristics in the vicinity of the discontinuities and then adopting appropriate integral boundary layer prediction techniques, methods are developed for continuing the boundary layer prediction process across them and then downstream of them. These computations compare well with experimental results, even for comparatively large discontinuities and the technique is recommended for use in a predictive role.