On Inviscid Modeling of Vortex-Wall Interactions

A vortex near the surface of an aerodynamic body necessarily results in the generation of secondary vorticity to enforce the no-slip condition on the boundary. Interaction between the primary and secondary vorticity can lead to modified vortex evolution, including weakening of the primary vortex through entrainment and cross-cancelation of the secondary vorticity. These phenomena are omitted in the inviscid modeling of vortex-dominated flows. In this study we investigate the physics of the vortex-wall interaction by comparing simulations of two revolving wings under identical inflow conditions. In one case the no-slip condition is applied to the full surface of the wing whereas in the other case, a free-slip condition is applied to the suction surface that interacts with the leading-edge vortex (LEV). A difference in LEV circulation is observed. A vorticity transport framework is used to elucidate differences in the evolution of the vortices between the two cases. Whereas in the no-slip case, the diffusive flux of secondary vorticity is found to be a significant factor regulating wing circulation, other transport mechanisms become more important in the free-slip case.