Aerodyamic Flow Control of an Airfoil with Small Trailing-Edge Strips

Abstract

The effects of small trailing-edge strips (Gurney flaps) on the steady and unsteady flow about a NACA0012 airfoil are computationally examined using a Navier-Stokes code, INS2D. Two Reynolds numbers, Re = 107,000 and 169,000, are used in the paper, the former corresponding to experiments previously reported in the literature and the latter corresponding to future proposed experiments. The computation of the unsteady flow includes an oscillating airfoil with several fixed Gurney flap sizes at higher angles of attack (beyond the stall angle of attack) and an oscillating Gurney flap with a fixed airfoil at higher angles of attack. For the former configuration, a correlation study between theory and a previous experiment has also been made. Reasonably good agreement with the experiment confirms the computational results that predict the effect of the Gurney flap is to enhance the maximum lift coefficient and stall angle of attack for both static and dynamic flows. The computations show that the effect of the Gurney flap is to move the separation position forward on the lower surface and back on the upper surface of the airfoil for near the trailing edge when the Gurney flap is oscillating. The oscillating Gurney flap increases the stall aerodynamic load.