Aerodynamic analysis of a helicopter in steady maneuvering flight using a free-vortex rotor wake model

The aerodynamics of a helicopter undergoing steady-state maneuvers has been studied using a free-vortex model of the rotor wake, The wake model is based on a finite-difference approximation to the vorticity transport equation, and is solved using a pseudo-implicit relaxation method, It is shown that, in both hover and forward flight, maneuvers are a source of additional distortion to the vortical rotor wake, This wake distortion can be sensitive to the maneuvering rates, In hover and low speed forward night, the maneuver induced wake distortion manifests as a counter intuitive change in inflow velocity through the rotor, This suggests that the free wake dynamics during pitching and rolling maneuvers may manifest as a contributor to the 'off-axis' blade napping response, At higher advance ratios, the effects of maneuver induced wake distortions are still present, but are reduced by about half relative to the hover condition, The results provide guidelines as to the importance of the main rotor wake in predicting the rotor napping response during maneuvers.