Aerodynamic design of the scaled supersonic experimental airplane

As a part of the NAL's scaled supersonic experimental airplane program to establish an aerodynamic design system based on Computational Fluid Dynamics (CFD), an aerodynamic configuration with no propulsion system was designed in a two-stage process. First, a baseline configuration was designed using a conventional linear theory. Then, the CFD and a supersonic inverse method were used to refine the wing geometry and to achieve a higher lift-to-drag ratio at a design point of M = 2 and CL = 0.1. A non-linear effect such as body to wind interference and a wing thickness effect were also handled in this phase. By making use of the inverse method, an upper surface of the wing was designed aiming at a natural laminar flow with a flat-type pressure distribution to reduce a friction drag. A wing warp was also adjusted to achieve an optimal load distribution designed by the linear theory to reduce a pressure drag. The designed new wing was evaluated by a Navier-Stokes analysis and an incompressible boundary layer stability code (SALLY code) and was found to have an improved lift-to-drag ratio, with a wider laminar flow regime and smaller friction drag than the initial geometry. Finally, the CFD analysis was compared with supersonic wind tunnel data and was found to be a well validated tool to be used in the design.