Free wake analysis of helicopter rotor flow fields using a coupled voricity embedding/fractional step method

A hybrid CFD (Computational Fluid Dynamics) method combining a potential-based Vorticity Embedding method with an Euler solver is presented and validated for isolated rotor flows First, a formulation of Vorticity Embedding is developed and validated for Cartesian grids This formulation is utilized together with simple lifting lines to represent an isolated rotor in hover The results for an isolated rotor are then compared with experiment The method is then hybridized by coupling the Vorticity Embedding grid containing the rotor to a region containing a ground plane where a standard finite difference Euler solver is utilized Initial results from this hybrid scheme are presented including a demonstration of the code's potential to calculate the ground vortex roll-up generated by a rotor in ground effect in the presence of a cross-wind