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.

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