PIV and Performance Measurements on Rotors Hovering above Inclined Surfaces

Phase-resolved particle image velocity measurements were taken to document the wake generated by a rotor operating in ground effect above inclined surfaces. In particular, the current work focused on the average wake structure and axial velocity distribution through the rotor. A two-bladed rotor was operated at a height of one rotor radius above a ground plane, and ground plane angles from 0° to 30° were investigated. Rotor performance measurements were also taken, using a six-axis load cell, to examine the effect ground plane angle had on the thrust produced and power required. The wake structure was found to be very sensitive to ground plane angle causing the radial distribution of axial velocity through the rotor to increase inboard and decrease outboard with increasing ground plane angle. The peak figure of merit of the rotor decreased with increasing ground plane angle.