Experimental investigation of the effects of different helicopter rotor tip geometries on aerodynamic performance and tip vortex characteristics

Abstract

In this study, the effects of different tip geometries (rectangular, anhedral, swept-tapered and swept-tapered-anhedral) on the rotor hover performance and tip vortex characteristics are investigated experimentally. A scaled rotor model set-up, instrumented with thrust and torque sensors, is used for aerodynamic performance measurements in hover and a two-dimensional (2D) particle image velocimetry (PIV) is used to obtain the tip vortex characteristics such as vortex trajectory, maximum tangential velocity, and circulation. Although taper+swept and taper+swept+anhedral configurations have the best ????/???? values at lower blade loadings, at higher blade loadings anhedral case has the best performance and an increase of 0.03 figure of merit compared to the baseline. It is observed that different tip shapes change the vortex trajectory, in addition, reduces maximum tangential velocity and circulation significantly. The PIV measurements which were performed at a high blade loading show that there is a correlation between the aerodynamic performance and the vortex strength.