Design and wind tunnel test investigation of the modern supercritical airfoil

In this paper, the aerodynamic design of modern supercritical airfoil is researched, the pressure distributions of outboard wing of two aircraft in service are analyzed at cruise and drag divergence point respectively, and some key points of supercritical section aerodynamic design are extracted. The class function/shape function transformation (CST) parametric method, Random weighted hybrid partical swarm optimization algorithm based on second order oscillation and natural selection (RwSecSelPSO), Reynolds averaged Navier-Stokes (RANS) equations and Kriging surrogate model combined with a kind of given expectation value cost function are used to establish the optimization system. In order to increase drag divergence Mach number and reduce the nose down moment, a series of airfoils satisfying the requirement but with different drag divergence Mach numbers is designed by the optimization system by adjusting the expectation value, meanwhile some airfoils with typical pressure distribution are compared and analyzed; the design principles and methods of improving drag divergence point and low-speed stall characteristic are verified and the airfoil which has flat topped pressure distribution at drag divergence point has better performance. Wind-tunnel tests are conducted for stall improvement method and transonic aerodynamic characteristic; the wind-tunnel test results indicate that the aerodynamic design satisfies the requirement and the stall improvement method is effective, while the laminar flow affects the stall characteristic dramatically.