Generalized aerodynamic and acoustic prediction for coaxial rotors in flight conditions

Abstract

Unmanned aircraft systems, including conventional drones and emerging urban air mobility, have revolutionized the industry by increasing productivity and innovation. However, rotor noise remains a major challenge, especially for coaxial rotor configurations, which are valued for their stability and maneuverability but suffer from significant noise emissions due to the complex unsteady flows. This study presents a rapid prediction model for the aerodynamic noise of coaxial rotors under various flight conditions, extending previous models that were primarily limited to hover. The proposed approach integrates blade element momentum theory with free vortex wake method for aerodynamic prediction, as well as an acoustic analogy for noise computation. The unsteady airfoil theory is used to evaluate unsteady loadings and predict noise emissions by analyzing vortex interactions. Validation against experimental data and high-fidelity simulations confirms the model’s accuracy in capturing both aerodynamic and aeroacoustic characteristics across different flight states. Based on computational efficiency, parametric analysis is conducted to investigate the effects of rotational speed, crosswind speed, and rotor spacing. The results highlight the model’s ability to capture noise patterns and provide actionable insights for noise reduction strategies.