Experimental investigation into effects of Gurney flaps on supercritical airfoil

An experimental study was performed on a supercritical airfoil in the FL-21 wind tunnel to investigate the lift-enhancement effects of the Gurney flaps at high speed conditions. The 0.5% C, 1.0% C, 1.5% C and 2.0% C height Gurney flap increased the maximum lift-coefficient by 6.0%, 12.4%, 21.7% and 22.3% separately, and the 1.5% C height Gurney flap increased the maximum lift-to-drag ratio by 33.2%. The mechanism of this increment in lift is that the pressure upstream of the Gurney flap was increased and the base suction downstream of it was increased also, and this difference in pressure led to an increment in circulation.