Analytical results of rotor blade‐ vortex interaction airloads are presented with two different wake models in the comprehensive analysis CAMRAD II, and these calculated results are compared with the experimental data obtained from the higher-harmonic-control aeroacoustic rotor test (HART-I) program. The HART rotor was a 40%, Mach-scaled model of the hingeless BO-105 main rotor. Two wake models used in the comprehensive analysis are the single-trailer and the multiple-trailer free-wake models. The multiple-trailer wake model shows good prediction of lift distribution, M 2 cn, as a function of azimuth for baseline, minimum noise, and minimum vibration cases, and shows signie cant improvement relative to the single-trailer model in prediction of the tip vortex wake geometry.

https://rotorcraft.arc.nasa.gov/publications/files/Lim_JAIR2003.pdf

Calculation of Rotor Blade-Vortex Interaction Airloads Using a Multiple-Trailer Free-Wake Model

Download reduction on a wing-rotor configuration

: The wake of a helicopter rotor consists of a relatively concentrated tip vortex generated by the rapid decrease in bound circulation at the tip of the rotor blade and distributed vortex sheets generated by spanwise variation of the bound circulation over the inboard portion of the blade (the inboard trailing wake) and by azimuthal variations of the bound vorticity (the shed wake). The tip vortex, because of its concentration, is best represented by a vortex line, with a finite vortex core where viscous effects dominate, and is responsible for the sharp peaks in the rotor airloads distribution. Thus accurate geometry is much more important for the tip vortex than for the rest of the wake and effort has been concentrated on the accurate and efficient computation of the tip vortex geometry.

M P Scully

Papers

On the computation of helicopter rotor wake geometry