超声速欠膨胀喷流噪声数值模拟研究

Numerical Investigation of Under-Expanded Supersonic Jet Noise

本文采用LES/FW-H混合算法开展超声速欠膨胀喷流噪声模拟,研究了欠膨胀状态下喷流流场与声场特征,发现欠膨胀喷流核心区下游平均流向速度衰减较理想膨胀喷流减缓,而湍流速度脉动值增大。此外,欠膨胀喷流中激波波系/喷流剪切层干扰增大了作用点附近的高频和低频压强脉动值,其辐射的宽频激波噪声增强了侧向与上游方向的高频噪声。通过分解近场声场,并结合激波波系的捕捉结果,详细给出了激波泄漏产生宽频激波噪声的过程,揭示了宽频激波噪声的产生机理。

The simulation of under-expanded supersonic jet noise is carried out using the LES/FW-H hybrid algorithm,and the characteristics of the flow-field and the acoustic field are studied.Compared with the ideally expanded jet,the decay rate of the mean streamwise velocity downstream of the potential core for the under-expanded jet is decreased,while the velocity fluctuation value is increased.It is found that the shock system/jet mixing layer interaction enhances the pressure fluctuation around the interaction point in the high-frequency and low-frequency range.The radiated broadband shock-associated noise increases the high-frequency noise in the lateral and upstream directions.By decomposing the near-field acoustic pressure and combining it with the shock system,the process of generating broadband shock-associated noise from shock-leakage is given in detail,and the generation mechanism of the broadband shock-associated noise is revealed.