Swept wings with subsonic leading edges
It is a well-known design principle to use two-dimensional airfoil flows in lower transonic or completely subsonic Mach number flows for the definition of swept wings in higher transonic or even supersonic Mach number flows. A shock-free transonic airfoil flow completely defines a family of 3D infinite wing flows yawed to upstream flow conditions with higher Mach numbers, with a relation between 2D and 3D Mach numbers Мд> * M^fcosfX), where Mjjj = M„ for the wing and Mjd = MN. the airfoil design Mach number and 3D Mach number component normal to the wing. Figure 40 shows an example, with characteristics evaluated for both 2D and 3D flow. The latter arc 3D Mach conoid traces and mark regions of influence and dependence; a coalescence of characteristics in the locution of 2D shock-free recompression illustrates the possibility of accumulative perturbation effects from distant span – wise locations in this area.
Figure 40 Using a 17% thick supercritical shock-free airfoil flow, <Mn s 0.707, C| * 0.6)
to define an infinite swept wing, = 60°. shock-free at M. = 1.414, CL = 0.15. Characteristics evaluation in supercritical airfoil flow and on swept wing upper surface.