On the computation of helicopter rotor wake geometry

TLDR: In this article, the authors present a model of the tip vortex line of a helicopter rotor, which 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.

Abstract: : 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.