伴流速度对平行喷口射流影响的数值研究

采用大涡模拟方法计算研究平行喷口出口马赫数为0.9,伴流速度比分别为0.1、0.3和0.5时的喷射流场特性。计算时采用高精度的数值模拟方法,并结合Smagorinsky亚网格尺度模型。考察了流场统计平均特性、脉动特性以及射流流场中涡结构的发展演变过程,结果表明:伴流速度的增大使得势流核长度变长,减缓了空间剪切层的发展,转捩延迟。喷射流场速度分布具有自相似性,而湍流强度的分布则不具有相似性。通过分析剪切层中轴向速度脉动、径向速度脉动、压力脉动在空间任意两点上的时空相关性,发现随着伴流速度的增大,脉动量在空间上的相关性减弱,而脉动量向下游的传递速率增加。该研究结果为进一步揭示伴流速度对喷流声场的影响提供基础。

Numerical investigation of influence of co-flow velocity on plane jet

The characteristics of plane jet were investigated by large eddy simulation, at the outlet of plane jet Mach number of 0.9 and the co-flow velocity ratio of 0.1, 0.3 and 0.5, respectively. High resolution numerical method and Smagorinsky sub-grid scale model were used. The mean flow properties, fluctuations and the evolution of the vortical structures were analyzed. Result showed that with the growth of the co-flow velocity, the potential core length increased while the development of the shear layer was slowed down and the jet transition was delayed. The velocity distribution was self-similar, but possible similarity in the turbulence intensity was not found. Two-point space-time correlations of the velocity and pressure fluctuations in the shear layer were investigated. It was found that the increase of the co-flow velocity weakened the space-time correlations, but accelerated the spreads of fluctuations to the downstream. This study provides a basis for revealing the effect of co-flow velocity on the sound field.