Optimization of a low Reynolds number airfoil with flexible membrane

Typical low Reynolds number airfoils suffer from reduced lift-to-drag ratio and are prone to flow separation. In order to improve the aerodynamic performance of such airfoils in an unsteady freestream, the concept of passive control is investigated. In this study, a membrane with varying thickness distribution and mechanical properties is attached on the upper surface of a modified Clark-Y airfoil and is free to move upwards and downwards in response to the pressure difference across it. The response surface method is employed to investigate the individual and collective effects of the membrane's prestress, elastic modulus, and thickness distribution on aerodynamic characteristics, as well as to optimize the performance of the airfoil. It is demonstrated that the aerodynamic performance of the airfoil can be improved with such a passive control approach based on the optimized design variables.