A Wind Tunnel Technique for the Identification of Ship Airwake/Rotor Downwash Coupling

A wind tunnel study is performed to analyze the interaction between ship airwakes and helicopter rotor downwash. This interaction is of interest to naval aviators and researchers as this phenomenon is thought to limit helicopter flight envelopes and increase the overall difficulty of maritime rotorcraft operations. In this study, a 1/50th scale simplified naval frigate model and appropriately scaled rotor model are used for all experimental work. A rotor thrust survey was conducted in the immediate vicinity of the landing deck. Two dimensional and stereo particle image velocimetry surveys and rotor thrust measurements with various rotor and ship configurations were conducted. Finally, a velocity based coupling analysis technique was developed and applied. In addition, extensive systems were developed to control wind tunnel conditions, accurately position wind tunnel models, manage data, and ultimately facilitate an efficient experimental process. The developed coupling technique quantifies aerodynamic coupling by examining 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 a wind tunnel speed of 5 m/s and zero wind-over-deck angle