A Wind Tunnel Investigation of Ship Airwake/Rotor Downwash Coupling using Design of Experiments Methodologies

摘要

A wind tunnel investigation was performed to examine the interaction between ship airwakes and helicopter rotor downwash. This interaction is known to limit helicopter flight envelopes and increase overall pilot workload. A simplified l/50th scale naval frigate model and appropriately scaled rotor model were chosen for this fundamental investigation. Particle image velocimetry (PIV) surveys were conducted to investigate the ship airwake/rotor downwash flowfield and to devise a velocity based coupling analysis technique to quantify the level of coupling between the rotor and airwake fiowfields. The developed coupling technique examines the component-wise velocity discrepancies between the experimentally observed flowfield and the flowfield generated by superposition. Significant aerodynamic coupling was found below a rotor-over-deck height of Z/D=1.2 for an advance ratio of 0.075 and zero wind-over-deck angle. Detailed rotor thrust surveys were conducted as a first step in correlating thrust changes to coupled regions.