Rotor Free-Wake Modeling using a Relaxation Technique – Including Comparisons with Experimental Data

A pseudo-implicit predictor-corrector relaxation method with five-point central differencing in space has been developed for the solution of the governing differential equations of the rotor free-wake problem. It is shown that this implementation exhibits good convergence characteristics of the rotor wake, but with only a moderate increase in computational expense compared to simpler methods. The present method is also generalized to allow unequal azimuth and wake segment angles that help maximize the fidelity of the results but minimize computational requirements. While the emphasis in this paper is on the numerical method itself, the results are compared with experimental measurements of the rotor wake geometry and flow field velocities in hover and forward flight.