Design of a Supercritical Airfoil

This article treats the development of several transonic airfoils. The initial design, NPU2, was based on a specified shockless pressure distribution at given design conditions which were Mach number, Reynolds number, and lift coefficient. Wind-tunnel tests substantiated the design. They showed up, however, weak shock waves. In a second step further optimization has been performed by Sobieczky's method. It led to the NPU2M airfoil. Finally, by introducing nonlinear recompression shapes on the upper surface these modifications resulted into two wing sections—NPUBS1 and NPUBS2—which had superior aerodynamic characteristics than the former one.