Assessment of Planform Effects on Rotor Hover Performance

Abstract

A hybrid Navier-Stokes/Free Wake methodology is applied to helicopter rotors in hover. Three tip planforms were analyzed: the S-76 rotor with a swept tip, a rectangular planform, and a swept tip with anhedral. The solidity of the three rotors was matched. A pitch sweep was conducted. Computed thrust, power, and figure of merit values have been compared with test data. Where available, comparisons with other calculations for these quantities and the near wake tip vortex trajectory have been done. The simulations are in reasonable agreement with published data for the thrust, power, and figure of merit. The simulations differ from full Navier-Stokes calculations in the predictions for tip vortex descent rate and contraction rate. The simulations correctly predicted the trends. The swept tapered anhedral tip had the highest figure of merit, followed by the swept tapered tip. The rectangular planform had the lowest figure of merit.