The Effects of Rotor-Rotor and Rotor-Wing Interactions on eVTOL Aeroacoustics

This study examines the effect of aerodynamic interactions on a two-rotor pair in cruise, and a propeller acting in the presence of a wing. The two-rotor system with a forward and an aft rotor in-line is considered at different disk loadings (6, 8, 12 lb/ft2 ) for a fixed cruise speed and different cruise speeds (20, 40, 60 knots) for a fixed disk loading. Loads for these rotors are generated using the CFD solver AcuSolve to capture the aerodynamic interactions on the rear rotor due to the front rotor. These loads are used as inputs to an acoustic solver (PSU-WOPWOP, ANOPP2) to predict noise at observers in the rotor plane, with noise compared to that from isolated rotors in the absence of aerodynamic interactions, to quantify the interaction effects. The rotor wing case, with the rotor in front of the wing operating in axial propeller mode, is simulated at 24 knots cruise and 8° wing angle of attack. Loads for the rotor with a wing and a rotor acting in isolation are generated using the CFD solver AcuSolve. These loads are used as inputs to an acoustic solver, with observers placed in the plane of the rotor, in the plane containing the wing chord cut through the rotor hub, and a vertical plane through the hub in the wind direction. The two-rotor system simulation results show that the presence of aerodynamic interactions on the rear rotor results in changes in noise levels of less than 2 dB in the plane of the rotors. The rotor wing results show that the aerodynamic interactions increase the overall noise by up to 8 dB, with the largest increase being above and behind the prop-rotor.