S弯喷管喷流噪声特性研究

Jet Noise Characteristics of S-Shaped Nozzle

关键词:  喷流噪声  S-弯喷管  FW-H方程  大涡模拟  指向性

Key words:  Jet noise  S-shaped nozzle  FW-H equation  Large eddy simulation  Directivity

摘要:

为了研究S弯喷管亚声速喷流的噪声特性，采用大涡模拟结合FW-H方程方法，通过数值模拟得到轴对称喷管和S弯喷管的流场及远场噪声。结果表明：S弯喷管的S形弯曲及圆转方构型导致了主流流向变化和横向压力梯度，S弯喷管出口截面角区及下方中心线附近均有不同尺度的旋涡分布，通过加强掺混减弱喷流与大气之间的剪切，使得S弯喷管噪声源尺度小于轴对称喷管。S弯喷管将St=0.08~0.2的噪声转移到St=0.2~0.3，在喷流下游10°~50°，S弯喷管相比于轴对称喷管噪声总声压级减小了6~8dB，在20°接收点处降噪效果最佳，相比于轴对称喷管减小了约8dB。在喷流上游S弯喷管降噪效果减弱，仅减小了2~4dB。在下游10°~80°处，S弯喷管水平探测面噪声总声压级比垂直探测面高2~3dB，在喷流上游二者差异较小。

Abstract:

In order to investigate the subsonic jet noise characteristics of the S-shaped nozzle， the large eddy simulation combined with the FW-H equation method is used to obtain the flow parameters and far-field noise of the axisymmetric nozzle and the S-shaped nozzle. The results show that the S-shape and round-to-square configuration of the S-shaped nozzle lead to changes of the main flow direction and lateral pressure gradient. There are vortexes of different scales in the corner area and center of lower wall of the exit section of the S-shaped nozzle. The vortexes could enhance blending and therefore weakens the shear between the jet and air， making the sound source of the S-shaped nozzle smaller than that of the axisymmetric nozzle. The S-shaped nozzle transfers the sound of St=0.08~0.2 to St=0.2~0.3， and at receivers of 10°~50° in the downstream， the overall sound pressure level of the S-shaped nozzle is reduced by 6~8dB， compared to the axisymmetric nozzle. The noise suppression at 20° is the most significant， which is about 8dB. The noise suppression in the upstream is weakened， which is only 2~4dB. At receivers of 10°~80° in the downstream， the overall sound pressure level on the horizontal plane of the S-shaped nozzle is 2~3dB higher than that on the vertical plane， and there is little difference between them in the upstream.