旋 翼 间 距 对 共 轴 刚 性 旋 翼 气 动 噪 声 的 影 响

A flow field simulation method for the rigid coaxial rotor is established based on Reynolds averaged NavierStokes equations and moving overset grid. Farassat 1A formulations are used for aerodynamic noise prediction. The effectiveness of the proposed methods is verified through comparison with relevant experiments. Research is conducted on the unsteady rotor thrust fluctuations and aerodynamic noise characteristics with different rotor spacing in hovering and forward flight states. Results show that with the increase of rotor spacing in the hovering state,the aerodynamic interactions of the two rotors are weakened. The thrust fluctuations and noise caused by interaction of blade-meeting are significantly reduced. Compared with that of the lower rotor,the noise of upper rotor caused by blade-meeting is weakened more significantly. The sound pressure waveforms of the upper rotor with different spacing are similar,while the waveforms of the lower rotor have significant changes. At the small advance ratio,the increase of rotor spacing changes the position and intensity of the interaction between the upper rotor blade tip vortex and the lower rotor. This kind of blade-vortex interaction noise is enhanced at a specific spacing. The effect of rotor spacing on aerodynamic noise is relatively small in high forward ratio states,while the noise reduction is more significant in low lift-offset states.