FREE-WAKE ANALYSIS OF TANDEM, TILT-ROTOR AND COAXIAL ROTOR CONFIGURATIONS

A free-wake model has been developed to predict the wake geometries of tandem, tilt-rotor and coaxial twin-rotor systems. The basic formulat ion is based on a pseudo-implicit, predictor-corrector, relaxation sch eme with five-point central differencing and velocity averaging in spa ce. Results are presented for three rotor configurations for several a dvance ratios ranging from relatively low speed to moderately high spe ed forward flight conditions. Comparisons have been made between compu ted and measured tip vortex geometries for the coaxial configuration, with good overall agreement.