Numerical Method for Simulating Rotor Flow Field Based upon Viscous Vortex Model

A new numerical viscous vortex simulation method is developed for unsteady rotor flow fields in which large-scale eddies are divided into small vortex particles.Vortex motion and transport processes are obtained by solving the Navier-Stokes equations represented in the vorticity-velocity form.The viscous diffusion term is calculated by a particle strength exchange method with high precision.The circulation of the blade bound vortex and new vortex particles are calculated by using the Weissinger-L lifting surface theory.To improve computational efficiency significantly,the fast multiple method(FMM) is introduced into the calculation of induced velocity and its gradient.By means of the above method,the rotor wake geometry and downwash of different rotors are investigated in hover and forward flight conditions.The validity of this method in rotor flow analysis is verified by comparing with available experimental data.Furthermore,the viscous vortex method is compared with the computational fluid dynamics(CFD) method and the traditional free wake method respectively.The comparison results indicate that the current method has the advantage of better rotor wake capture over the other methods while maintaining efficiency.