火箭整流罩内降噪装置低频声学性能仿真

针对运载火箭整流罩内降噪装置所具有的特殊曲线颈部Helmholtz共鸣器，基于仿真方法研究降噪装置的低频声学性能.应用虚拟阻抗管法分析了Helmholtz共鸣器共振频率及吸声系数与其壁面厚度的变化关系.研究了降噪装置不同安装位置对圆柱空腔内平均声压级的影响.仿真结果表明，随着壁面厚度增加，Helmholtz共鸣器共振频率逐渐趋于刚性壁面的值，但吸声系数先增大后减小.降噪装置不同的安装位置可使空腔内平均声压级相差10 dB以上，在工程应用中需将其放置于空腔模态振幅较大的位置. 

Simulation on the Low-Frequency Acoustic Performance of Noise Attenuation Device in Launch Vehicle Fairings

For a special curved neck Helmholtz resonator that exists in the noise attenuation device used to reduce noise in launch vehicle fairings, its low-frequency acoustic performance was investigated numerically. A virtual impedance tube method was adopted to find out the effect of wall thickness on resonance frequency and sound absorption coefficient of the Helmholtz resonator. The effect of noise attenuation device with different installation locations on the average sound pressure level of a cylindrical cavity was analyzed. The simulation results show that as the wall thickness increases, the resonance frequency increases gradually and tends to the value of rigid wall, but the sound absorption coefficient increases firstly and then decreases. The different installation locations of noise attenuation device can result in 10 dB changes of average sound pressure, so the device should be installed on the larger modal amplitude position of a cavity mode.