1993 年 41 巻 471 号 p. 213-221
Three-dimensional boundary layers include a velocity component normal to outside potential flows and thereby become unstable much earlier than two-dimensional cases. There are two causes contributing the cross-flow in boundary layers along a swept wing, one of which is the pressure gradient in the direction normal to wing leading edge and the other the pressure gradient along the leading edge. The latter does not appear in the case of infinite sheared wings, but exists in a usual swept wing with finite span, in particular when it is tapered, and is surely expected to affect stability characteristics of the boundary layer. Thus a simple and approximate procedure of boundary-layer calculations and stability calculations is presented for a purely three-dimensional flow around a slightly tapered wing. Then the method is applied to the boundary layer along a yawed cylinder to show important effects of sweep angle and taper ratio on the diagram of critical Reynolds numbers.