A Nonlinear Vortex Lattice Method for Unsteady Flow with Separated Vortex

An improved Nonlinear Vortex Lattice Method is presented to simulate steady and unsteady flows for wings with leading edge and/or tip vortex separation at moderate or high angles of attack. A new type of vortex lattice shape along the leading edge is introduced and a multi-step method is presented for determining the position of the free vortex sheets which move downstream in the flow field. It is shown that this method can predict much more stable results for wings with leading edge separated vortex when undergoing very rapid and large amplitude movements. The calculated airloads agree well with the experiments.