Helicopter rotor tip shapes for reduced blade vortex interaction - An experimental investigation

Abstract

Mach numbers of 0.75 and 0.78 with respective chord Reynolds numbers of 3.2 and 5.6 million. The latter Mach number-Reynolds number pair provide a full-scale operational match for the candidate rotor tip planforms. Total pressure surveys of the wake were conducted at three chordwise stations aft of each model at an equivalent rotor pitch angle of 8 deg. These tests revealed the initial roll-up region and provided a comparison of the effects of Mach number, Reynolds number, and tip shape on the vortex size, shape, location, and minimum stagnation pressure. The swept and swept-tapered planforms produced larger, more diffuse, tip vortices than the rectangular or tapered planforms. (Author)