Numerical Investigation of the Effect of Leading Edge Geometry on Dynamic Stallof Airfoils

摘要

The dynamic stall of rapidly pitching and oscillating airfoils is investigated bythe numerical solution of the full compressible unsteady two-dimensional Navier-Stokes equations using an alternating-direction-implicit scheme. The flow is assumed to be fully turbulent, and the turbulent stresses are modelled by the Baldwin-Lomax eddy viscosity model. Three airfoils (NACA 0012, NACA 0012-33, and NACA 0012-63) are analyzed for the purpose of examining the influence of leading-edge geometry on unsteady flow separation. It is found that a larger leading edge radius, thicker contouring of the forward part of the airfoil, or increasing reduced frequency results in delaying flow separation and formation of the dynamic stall vortex to a higher angle of attack, yielding higher peak Cl. Within the scope of this study, the pressure gradient encountered by the flow at initial separation is found to be independent of reduced frequency and freestream speed. The critical pressure gradient is dependent on leading edge radius and increases for decreasing leading edge radius.