Simulation Analysis of Aerodynamic Noise of Highspeed Compound Helicopter with Twin Propellers in Different Flight States

The twin-propeller high-speed composite helicopter is studied using aeroacoustics simulation method, aiming to reveal its noise generation mechanism in different flight conditions and provide a theoretical basis for low-noise design. Based on the mixed-precision CFD and acoustic analogy (FW-H equation) coupling method of the whole helicopter, combined with the sliding grid and overset grid technology, an unsteady aerodynamic noise prediction model was established. Three states of hovering, low-speed forward flight and high-speed forward flight, the noise composition, directivity and frequency domain characteristics of the coupling between the isolated parts and the whole aircraft were analyzed, respectively. The results show that during hovering, propeller noise is the primary component, with vortex shedding at the blade tips concentrating at the bottom of the fuselage to form intense interference, reaching a peak of 105 dB; during the low-speed forward flight phase, rotor vortices are the main source of interference noise, peaking at 104 dB near the lower side of the rotor disk plane on the forward side; in high-speed forward flight, rotor noise remains the dominant factor, with reduced interference from various components but increased sound source concentration, also located below the forward side away from the rotor disk plane, reaching a peak of 106 dB.