Optimization of a flexible low reynolds number airfoil

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 optimized 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. A parametric evaluation of the membrane's prestress, elastic modulus and thickness distribution is conducted to generate response surfaces for optimization. A reduced fifth order polynomial shows the best agreement to the data used for the regression analysis. The result shows that the aerodynamic performance of the airfoil can be improved with such a passive control approach based on the optimized design variables.