Flap-deflection optimization for transonic cruise performance improvement of supersonic transport wing

Wing flap-deflection angles of a supersonic transport are optimized to impr ove transonic cruise performance. Toward this end, a numerical optimization method is adopted using a three-dimensional unstructured Euler code and a discrete adjoint code. Deflection angles of 10 flaps, five for leading edge and five for trailing edge, are employed as design variables. An elliptic equation method is adopted to enable interior grid modification during the design process. Interior grid sensitivities are neglected for efficiency. A lso tested is the validity of the approximate gradient evaluation method fo r the present design problem; it is found to be applicable for leading-edge flap design in cases where there are no shock waves on the wing surface. T he Broydon-Fletcher-Goldfarb-Shanno method is used to minimize the drag wit h constraints on the lift and upper surface Mach numbers. Two design proble ms are considered; one involves a leading-edge flap design, and the other i nvolves simultaneous design of leading-edge and trailing-edge flaps. The la tter gave a smaller drag than the former by about two counts. Successful de sign results suggest that the present design method is valid and efficient.