Application of the alula to two-dimensional airfoil for aerodynamics performance enhancement

Abstract

In the present study, we applied the alula at the leading edge in avian wing to two-dimensional airfoil for aerodynamic performance enhancement. For this study, we designed experiment which is able to compare between the result by using base airfoil and its by airfoil with alula-shaped device. The section shape of main wing and the alula was chosen as SD7003 and experiment was conducted at Re = 100,000. Force and velocity around the airfoil was measured for two cases. As a result, the alula model enhances the lift coefficient and also decrease the drag coefficient at the attack angle which stall occurs. Thus, it increases the lift-to-drag ratio also, because inflow through small slot of alula model gain more momentum than base airfoil model, streamwise velocity gradient is larger and strength of Reynolds shear stress is smaller at the upper surface of the alula model. With this results, we read off the reasons of decreasing the drag and hence enhancing aerodynamic performance.