The flow physics of a multi-element airfoil in ground effect is studied by numerical simulation. The steady compressible Reynolds-Averaged Navier-Stokes equations in conjunction with the Spalart-Allmaras turbulence model are solved using the finite volume method. For a single-element airfoil, the camber of the airfoil is relatively small and therefore the reduction in effective camber due to ground effect is weak and the blockage effect in ground effect is strong. The pressure increment on the lower surface of the airfoil is larger than that on the upper surface; thus the lift in ground effect increases. For a multielement airfoil however, the camber is very large and therefore the reduction in effective camber in ground effect is large and the blockage effect is weak. Thus the pressure increment on the upper surface of the multi-element airfoil is larger than that on the lower surface, and therefore the lift in ground effect decreases.
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