Numerical Simulation on Aerodynamics of Multi-Element Airfoil with Drooped Spoiler in Ground Effect

By using the finite volume method and k-ω SST turbulence model to solve the Reynolds Average Navier-Stokes equation and using the slipping wall to simulate the relative movement of the ground, the ground effect on the aerodynamic characteristic of multi-element airfoil with drooped spoiler is investigated numerically, and the reason why the lift coefficient decreased in ground effect is analyzed. The results indicate that, with the reduction in ride height, the lift and the drag decrease and the lift-drag ratio increases for the multi-element airfoil; the amplitude of the reduction in the lift coefficient increases with the reduction in ride height and the increase in the angle of attack, the maximum of lift coefficient can be reduced by about 22%; with the effect of ground, the losses of suction at upper surface make the lift decrease, the increases of pressure at lower surface make the lift increase, the variation of the lift coefficient for the main wing caused by the former is more than three times that of the latter. Analyzing the reason why the lift coefficient decreases showed that:on the one hand, ground effect on the lift coefficient for clean airfoil is changed with the range of angle of attack. For the low-to-moderate angle of attack, the lift coefficient increases; for the high angle of attack, the lift coefficient decreases. But multi-element airfoil works in the takeoff and landing stage for the high angle of attack, which causes the reduction of the lift coefficient in ground effect. On the other hand, the increase of the lift coefficient caused by the deflection of spoiler decreases with the reduction in ride height and the maximum reduction can be about 50%, which illustrates that ground effect makes interaction of the front and back section for the multi-element airfoil weak, resulting in further decreasing the coefficient for the multi-element airfoil.