低中等雷诺数超声速轴对称射流气动声场

Aerodynamic acoustic field of axisymmetric supersonic jet at low and moderate Reynolds number

采用线性抛物化稳定性方程(LPSE)方法对低、中等雷诺数条件下的超声速轴对称射流进行了研究。结果表明:射流中不稳定波的增长特性决定了声辐射的特性。在低雷诺数条件下,不稳定波的频率范围较窄,且由于不稳定波的增长区间较长,因此声辐射的范围较宽,声源不集中,声辐射的方向角不明确。在中雷诺数条件下,不稳定波的频率范围较宽,且由于不稳定波的增长区间较短,因此声辐射的范围较窄,声源集中,声辐射的方向角较明确;且随着斯特劳哈尔数增加,声辐射的方向角增加。在低雷诺数条件下,射流基本流的法向速度对射流气动声场的影响较弱,而在中等雷诺数条件下,其对射流的气动声场影响较强。

Acoustic field properties of an axisymmetric supersonic jet at both low and moderate Reynolds numbers were studied using the linear parabolized stability equations（LPSE）.The results showed that,the dominant noise-generation mechanism was determined by the characteristics of unstable wave.When Reynolds number was low,the unstable wave frequency band was relatively narrow.Since the unstable region of the disturbance wave was long along stream wise direction,the acoustic radiation region was large;the sound source was decentralized;and the radiation angle was hard to be determined.For moderately large Reynolds number,the unstable wave had a large unstable frequency wave band;the short unstable region resulted in a narrow radiation region,concentrative sound source and strong radiation directivity;and the direction angle increased with the increase of Strouhal number.The normal velocity had a negligible effect on the acoustic field for low Reynolds number,while it had to be taken into account when Reynolds number was large.