Adjoint shape optimization of airfoils with attached Gurney flap

A Gurney flap is a vertical short strip mounted perpendicularly to the pressure side of an airfoil in the vicinity of the trailing edge. It has remarkable effects on the aerodynamics of wings in producing higher lift. However, the drag also increases due to the flow separation caused by the Gurney flap down-stream of the trailing edge. In the present paper, the adjoint shape optimization process is used to minimize the drag coefficient of airfoils with the Gurney flap in order to decrease its unfavorable effects on the drag coefficient. Gurney flaps with different heights attached to the NACA 2412 and NACA 4421 airfoils in different Mach numbers are optimized. The results show that adjoint shape optimization eliminates the unfavorable effects of the Gurney flap on the drag coefficient considerably.