Abstract: Aerodynamic design optimization is to find the optimum of aircraft aerodynamic performance under certain constraints by changing the shape of the designed object. It facilitates the design process by automating both the performance analysis and the optimization method. Aerodynamic design optimization is an integrated application of geometry parameterization, grid update, flow field solver and optimization method, and it has contributed to the design of aircraft with the maturity of computational fluid dynamics (CFD) and the progress of computer performance.This paper presents an aerodynamic wing shape optimization method based on non-uniform rational B-spline (NURBS), in which the mesh deformation is used with a spring-based smoothing method. The Reynolds-averaged Navier-Stokes equations with an algebraic turbulence model of Baldwin-Lomax are used to solve the flow field, and a discrete-adjoint method inexpensively computes the sensitivities of the function with respect to design variables, to build the gradient of the objective function. Finally, an sequential quadratic programming (SQP) method is employed to find the optimum. An aerodynamic shape optimization is performed to minimize the drag of wing ONERA M6 at transonic Ma=0.84 and α=3.06°. As a result of the optimization, the pressure coefficient on the up-wing surface is changed obviously, and the λ shock wave is much reduced. The drag coefficient loses 25 drag counts, which means a 13.1% drag improvement with the constraints of the lift and volume. This application to an aerodynamic design optimization validates the system of optimization and design based on NURBS.

Key words: non-uniform rational B-splne, geometric parameter, aerodynamic shape optimization, ONERA M6 wing, numerical simulation