热喷射流动大涡模拟及网格敏感性评估

Large Eddy Simulation of Hot Jets and Evaluation of Grid Resolution

采用大涡模拟计算研究渐缩圆口喷管的热喷射流动,声学马赫数为0.75,出口温度与环境温度比T_j/T_∞分别为1.0、2.0和3.0的三种情况,分析喷流温度对声源流场的影响。首先通过外推法对两种尺度的网格进行敏感性分析,评估网格分辨质量。在此基础上,研究喷流出口温度比变化时的流场,发现随着温度比升高势流核长度逐步缩短,势流核心区下游剪切层厚度降低,这与旋涡的破碎速率加快和对流速度的降低有关。本研究为进一步分析温度梯度对喷流声源流场和辐射声场的影响提供了基础。

Large eddy simulation(LES)of compressible hot jets at acoustic Mach number of 0.75 was carried out.Three cases with temperature ratio of the jet to the ambient,at 1.0,2.0 and 3.0 respectively,were investigated.The purpose was to study the temperature effects on the flow field,which was the source of radiated sound.Prior to presenting the flow details,the grid resolution was evaluated using an extrapolation method for turbulent kinetic energy.The predicted turbulence properties at the three temperatures were compared.It was shown that with the increase of temperature ratio,the potential core became shorter,while the thickness of the shear layer in downstream of the potential core was reduced.These were related to both the accelerated fragmentation of large scale vortices and the slow-down of the convection speed.A basis for further study of noise radiation from heated jets was provided.