A numerical method combining computational fluid dynamics (CFD) method and Ffowcs Williams–Hawkings (FW–H) equations is established for predicting acoustic characteristics of the coaxial rigid rotor in hovering and forward flight. The unsteady Reynolds-averaged Navier–Stokes (URANS) solver coupled with the moving-embedded grid technique is established to obtain sound source information in the flowfield with high accuracy. On the basis of the accurate solution for the coaxial rotor flowfield, the blade–vortex interaction (BVI) noise in hovering state and the high-speed impulsive (HSI) noise in high-speed forward flight are estimated by the Farassat 1A formula and the FW–H equation with a penetrable data surface (FW–H_pds), respectively. Then the sound pressure distribution characteristics and sound radiation pattern for the coaxial rotor in a hovering state and in a forward flight are obtained through the comparative analysis of the sound pressure time histories and the distribution of sound pressure levels of the upper rotor, lower rotor, and coaxial rotor. The simulation results indicate that significant unsteady characteristics appear in blade aerodynamic loading due to the Venturi effect, blade–vortex interaction phenomenon, and action of the downwash existing in the coaxial rotor flowfield, causing the loading noise of the coaxial rotor to occupy the dominant position in hovering state; the counter-rotating characteristics of the upper and lower rotors cause a significant phase difference between their respective sound pressure waveforms, and the phase difference is determined by the angle between the observation point and the intersection position of the upper and lower blades; the difference with the single rotor in terms of the severe HSI noise generated in the high-speed forward flight is that the noise radiation intensity of the coaxial rotor along both sides in the forward direction exhibits an approximately symmetrical distribution.

建立了一种结合计算流体动力学（CFD）方法和 Ffowcs Williams-Hawkings（FW-H）方程的数值方法，用于预测悬停和前飞的同轴刚性转子的声学特性。建立了非定常雷诺平均纳维-斯托克斯 (URANS) 求解器，结合移动嵌入网格技术，以高精度获取流场中的声源信息。在对同轴转子流场精确求解的基础上，利用 Farassat 1A 公式和具有可穿透数据表面的 FW-H 方程 (FW-H _pds）， 分别。然后通过对比分析上旋翼、下旋翼、下旋翼的声压时程和声压级分布，得到同轴旋翼在悬停状态和前飞状态下的声压分布特性和声辐射模式。和同轴转子。仿真结果表明，由于文丘里效应、叶片-涡流相互作用现象以及同轴转子流场中存在下洗流的作用，叶片气动载荷出现显着的非定常特性，导致同轴转子的载荷噪声占据主导地位。悬停状态；上下转子的反向旋转特性导致它们各自的声压波形之间存在显着的相位差，相位差由观察点与上下叶片相交位置的夹角确定；与单旋翼高速前飞产生的剧烈HSI噪声不同的是，同轴旋翼沿前向两侧的噪声辐射强度呈近似对称分布。