Effects of Surface Ice Roughness on Dynamic Stall

A two-dimensional Navier-Stokes algorithm is used to investigate unsteady, incompressible viscous flow past an airfoil leading edge with surface roughness that is characteristic of early-growth ice accretion. The roughness is added to the surface through the use of a Prandtl transposition and can generate both small-scale and large-scale roughness geometries. The algorithm is used to simulate steady or unsteady flow at constant angle of attack or pitch up corresponding to dynamic-stall conditions. Investigations of the dynamic stall show that some types of surface roughness can significantly alter the unsteady flow separation pattern and the formation of the dynamic-stall vortex. This includes both small-scale and large-scale roughness.