Helicopter rotor BVI airloads computation using advanced prescribed wake modeling

Abstract

The miss-distance between helicopter rotor blades and their tip vortices is a key parameter for the correct prediction of blade-vortex interaction noise. Either free-wake codes (vortex lattice methods) or computational fluid dynamics codes are usually applied to compute the wake geometry and the blade-wake interactions. Prescribed wake codes are rather fast in computation, since the wake-vortex interactions are ignored therein, but they are considered not to be accurate enough due to the prescription of the geometry based on a few general parameters. They lack the effect of rotor harmonic loading and the effect of the fuselage on the wake geometry. This paper provides an approximate solution for both problems as independent extensions to classical prescribed wake codes to a first order of accuracy.