Low speed boundary layer and pressure distribution tests on a family of swept back wings

Abstract

Low-speed tests were conducted to determine boundary layer and surface pressure distribution characteristics of a systematic family of swept back wings. It is intended that the test results will have application in giving a better understanding of the viscous flow phenomena on swept back wings, particularly in relation to the stall. A general picture of the boundary layer flow and surface pressure distribution at high lift conditions, showing the effects of variations in wing planform, was determined. Several existing concepts were verified and an attempt was made to define the limits of applicability of these concepts. A localized separation of the flow perpendicular to the leading edge of the wing, hereinafter referred to as the flow, was found to occur at lift coefficients somewhat below the stall on the wings with appreciable sweepback. The separation took the form of a vortex streak running aft and outboard from an origin near the leading edge, and it greatly affected the boundary layer structure and the surface pressure distribution. Generalization of surface pressure distribution on the basis of the local lift coefficient and dynamic pressure for the normal flow was found to hold fairly well for the various sweepback angles. The development of stall was determined for the various planforms in terms of boundary layer thickness and flow direction near the surface of the wing. Generalization of the shape of the profiles of the normal boundary layer flow component in terms of a single family of shapes for all sweep-back angles, as suggested by other researchers, was shown to be possible.