Separation Jump and Sudden Stall over an Ellipsoidal Wing at Incidence

Abstract

Abstract : To obtain complete and rigorous solutions of the three-dimensional, laminar boundary layer over a finite airplanewing, a flat ellipsoid was chosen as a model to generate concrete results. Initial efforts were directed toward calculating the inviscid flow and the selection of coordinate system, and this was followed by a detailed investigation of the boundary layer restricted to the symmetry-plane. This investigation showed that as the incidence increases, the separation point on the upper surface does not always move continuously forward; instead, it first moves forward and later rearward. Then, at a critical incidence, it jumps forward and moves thereafter close to the leading edge. This 'separation jump' phenomenon was further found to be little affected by varying the span, but critically dependent on the chord: a longer chord prompts a larger jump. Although such separation jump has been reported for a body of revolution, it has not yet been reported for wing surfaces. The significance of this phenomenon is apparent when one considers that the separation jump may well occur on airplane wings in general and probably accounts for what we might call 'sudden stall'. (Author)