Experimental Wind-Tunnel Testing Of Rotor/Wake Aerodynamic Interactions On A Compound Helicopter

Abstract

The compound helicopter configuration has gained renewed interest as a low-range, high-speed rotorcraft. Given the proximity of main rotor and propellers, this configuration is characterised by the aerodynamic interaction between these elements. To investigate the extent of these interactions, a wind-tunnel test campaign was carried out on a model rotor equipped with two lateral propellers, and numerous flight conditions were tested, including low-speed forward flight and crosswind, to study the impact on the aerodynamic performances of the rotors. Numerical simulations with a mid-fidelity code were also performed to further examine the interactional behaviour. The results show an important influence of the main rotor on the propellers, causing a general increase in the generated thrust and in the efficiency, directly related to the main rotor's downwash. A singular occurrence of thrust decrease highlights the complexity of the aerodynamic interactions and their dependence on the flight conditions.