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

Abstract

The dynamic stall of pitching airfoils is investigated by the 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. The objective of this study is to investigate the influence of the leading edge geometry on unsteady flow separation. For this purpose three airfoils are analyzed, namely, the NACA 0012 baseline airfoil, the NACA 0012-63 having the same leading edge radius but different contouring forward of maximum thickness, and the NACA 0012-33 having a smaller leading edge radius. It is found that a larger leading edge radius, thicker contouring of the forward part of the airfoil, or increasing pitch rate results in delaying flow separation and formation of the dynamic stall vortex to a higher angle of attack, yielding a higher peak lift coefficient. Within the scope of this study, incipient flow reversal was found to occur in response to essentially the same critical pressure gradient distribution for different pitch rates and Mach numbers.