Stall alleviation using a deformable leading edge concept

The dynamic stall characteristics of conventional airfoils used in helicopter blades, and airfoils whose shapes change dynamically with time are numerically studied. Two-dimensional Navier-Stokes equations in integral form are solved on a body-fitted grid that deforms as the airfoil changes its shape, and rotates with the airfoil in pitch. The scheme is second order accurate in time and space. The effects of turbulence are accounted for using a two-layer eddy viscosity model. The computed surface pressure distributions and the integrated loads show that the dynamically deforming leading edge airfoil has a superior performance compared to the NACA 0012 airfoil. It tends to have lower pitching moments, milder stall, and lower drag characteristics. The difference between the two flow fields is striking, given the fact that the airfoil deformations are rather small.