The Boundary Layer on a Townend Surface

Abstract

SummaryCertain three-dimensional surfaces studied by Townend have the property that at every streamwise section a supersonic air stream is compressed isentropically in the form of a reversed Prandtl-Meyer flow. If all the compressions are centred on points lying on one straight line the flow is conical. Such a surface may be of use as an engine intake. In this paper an approximate boundary-layer calculation for such a surface is made for laminar flow with zero heat transfer in the conical case. It is found that under certain circumstances a useful amount of compression can be obtained before separation occurs (a pressure ratio of 6, for instance, for an initial Mach number of 10). Limiting streamlines are drawn and displacement thickness calculated for a typical case, and the Mach number at separation is determined for a range of initial Mach numbers and angles of sweep. Instability due to sweep is considered.