INSTABILITY WAVES DEVELOPING FROM A POINT-SOURCE NEAR THE ATTACHMENT LINE ON A YAWED CIRCULAR-CYLINDER

The boundary-layer flow near the leading edge of a swept wing is susce ptible to two kinds of instabilities; namely, the cross-flow instabili ty and the streamline-curvature instability. Each of them should be re sponsible for propagation and growth in the downstream direction of sm all disturbances that may be introduced by a gust in the external stre am or a local roughness of the wing surface. The present study, theref ore, investigates development of wedge-shaped disturbances originating from a point source placed near the attachment line on a yawed circul ar cylinder by the use of an approximate boundary-layer calculation, l inear stability theory including fundamental effects of wall and strea mline curvatures and the method of complex characteristics for descrip tion of dispersive waves. Computational results indicate that the stre amline-curvature instability dominates the flow field just downstream of the attachment line, when the uniform-flow Reynolds number is only a little higher than the critical value or when the sweep angle of the cylinder is extremely small.