Aerodynamics of a multi-element airfoil near ground

Two-dimensional wing sections were investigated numerically both in clean and high lift configurations operating in ground effect. The compressible Navier-Stokes equations are solved by the finite-volume method, and shear-stress transport k-w turbulence model is used. The effects of flight height on the aerodynamics of the multi-element airfoils are found obviously different compared with clean airfoils. The results indicate that, with a reduction in height, the lift increases for the multi-element airfoil, but decreases for the clean airfoil, while the drag and nose down moment decrease for both airfoils. The cause of the reduction of lift is that the losses of suction side of upper surface are more than the increases of pressure side of lower surface. The separated region becomes larger as the height reduces.