关键词: 共轴刚性旋翼, 气动噪声, 运动嵌套网格, CFD, 旋翼间距

Abstract: A flow field simulation method based on Reynolds averaged Navier Stokes equations and moving overset grid was established for rigid coaxial rotor. Farassat 1A formulations were used for aerodynamic noise prediction. The effec-tiveness of the established methods was verified through comparison with relevant experiments. Researches were conducted on the unsteady rotor thrust fluctuations and aerodynamic noise characteristics under different rotor spac-ing in hovering and forward flight states. Results show that with the increase of rotor spacing in hovering state, the aerodynamic interactions of the two rotors are weakened. The thrust fluctuations and noise caused by the interaction of the blade-meeting are significantly reduced. Compared with 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 small the advance ratio, the increasing 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.

Key words: rigid coaxial rotor, aerodynamic noise, overset grid, CFD, rotor spacing