S 弯喷管喷流噪声特性研究

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.