SUPERSONIC WINGS

This section deals with wings operating at free-stream Mach numbers greater than unity. Since the governing flow equations change their form in going from subsonic to supersonic flow, the behavior of a wing changes its characteristics also. The induced drag, lift curve slope, and center of pressure are all affected significantly when M„ exceeds unity.

There are many variations possible in supersonic wing configurations, so that it is almost impossible (at least with the current state of the art) to present a universal approach that will satisfy the intended level of this text. Instead, we will examine two specific cases. The first case is that of swept wings (including delta wings) with subsonic leading edges and supersonic trailing edges; the second case is that of swept or unswept wings with supersonic leading and trailing edges. The term “subsonic leading edge” may be somewhat misleading. It refers to the case where the leading edge lies within the Mach cone generated at the apex. The Mach number normal to the edge is subsonic, so that even though such a wing is supersonic, because of the independence of the normal flow, it exhibits some of the characteristics of a subsonic wing (such as a leading edge suction force).

No attempt will be made to develop the theory of supersonic wings. Instead, a brief description will be offered of each theoretical approach together with the limitations. Results will then be presented that permit estimations of wing behavior in supersonic flow. We begin with the case of subsonic leading edges.