THE EFFECT OF VECTORED INJECTION ON THE LOCATION OF SEPARATION

Abstract : It was previously established that the vanishing of the skin friction is not the appropriate criterion for separation over boundaries with non-zero boundary conditions. It was recently shown that the correct criterion coincides, in the boundary-layer model with the separation singularity. These ideas have immediate application to separation control through blowing. A few characteristic cases are studied for blowing perpendicular or parallel to the wall. The effect of the angle of injection is also investigated for a fixed value of the blowing flow rate. It is found that whereas blowing in general shifts separation upstream, a small angle of injection may easily push the location of separation to the downstream direction. Another interesting feature of the phenomenon is that separation seems to be affected mainly by the local properties of injection. It is also indicated that for an angle of injection equal to 63.5 degrees, the location of separation is independent of the magnitude of the injection velocity. (Author)