High-fidelity numerical investigations of rotor-propeller aerodynamic interactions

Abstract

This paper presents high-fidelity numerical investigations of rotor/propeller aerodynamic interactions related to thrust-augmented compound rotorcraft. High-fidelity CFD simulations of a generalised rotor/propeller integration, as studied both numerically and experimentally by ONERA, were performed using the HMB3 solver within the GARTEUR AG25. Simulations of the baseline isolated propulsors were first carried out and validated against experimental measurements. Simulations of the rotor/propeller integration were then performed and compared with ONERA numerical results. Evaluations of the spatial/temporal resolutions were first carried out at low-speed forward. The actuator disk modelling of the main rotor was shown to be an effective and efficient simulation method compared to blade-resolved results. Simulations of the installed propeller were also performed in hover, and the aerodynamic interference was found to be considerably exacerbated. A ducted propeller configuration was also proposed to study how ducting the propeller would change the aerodynamic interference. The duct offloaded the propeller and produced extra thrust, and the blades suffered less from the main rotor downwash. However, the duct generated a strong downwards force and a nose-down pitching moment because of its flow blockage. The loading variations induced by the aerodynamic interactions were found to be strong at low advance ratios but ducting provided significant alleviation.