Potential Panel and Time-Marching Free-Wake-Coupling Analysis for Helicopter Rotor

Abstract

A potential-based panel method coupled with advanced time-marching free-wake techniques is developed to achieve fast and accurate prediction for unsteady aerodynamics and wake dynamics of helicopter rotating blades. This coupling analysis is enabled by using the equivalence of the doublet-wake panels and the vortex filaments. The coupled panel method allows the inclusion of the self-induced velocity of curved vortex filaments and high-order time integration for the computation of wake convection. A parallel computation is applied to the wake convection for fast numerical calculation. The computation of the induced velocity from each vortex filament is parallelized and computed separately. The velocity-field integration technique is used to avoid numerical singularity during the interaction between the wake and blades. It is found that blade-pressure predictions and the wake roll-up agree well with the measured data for helicopter rotors, both in hover and forward flight. Tip-vortex pairing phenomena are also predicted and compared with the measured data.