A Lifting-Surface Method for Hover/Climb Airloads

The development of a lifting-surface method for hover/climb airloads and its application in the prediction of hovering rotor performance are described. The method includes both a prescribed and a relaxed wake representation. Unique features of wake modeling developed for the method include the wake segmentation, a new far-wake model, and a model of the tip vortex shedding across the blade chord. In addition, new techniques for wake relaxation, such as a numerical method for the calculation of wake velocities due to curved vortex filaments, a more representative core model, and a new method of integration for new wake shapes are discussed. Calculated results demonstrate that the fundamental explanation for discrepancies in hovering rotor airloads predicted by lifting-line and lifting-surface methods is the wake shedding model. Finally, hovering performance correlations for converged relaxed wake calculations with experimental data are analysed.