稳态射流数值模拟中速度参量对传热的影响机制分析

Analysis of impact mechanism about velocity parameters on heat transfer in the numerical simulation of steady jet

对文献中多个槽缝冲击射流的经典实验结果进行数值模拟,考察RNG k-ε和Transition SST湍流模型的表现,主要分析射流出口中心线和展向、壁面射流区域的雷诺时均速度和湍流度分布,以及靶面换热效果与流场模拟结果之间的关系.模拟结果表明,与Transition SST湍流模型相比,RNG k-ε模型的结果表现出更强的湍流粘性,使得其中心线上速度衰减较快,该效果可能导致低估靶面上的冲击换热效果;而在冲击滞止区域,RNG k-ε湍流模型结果表现出过高的湍动能,该效果可能导致高估靶面上的冲击换热效果.因此,当射流雷诺数较小时,Transition SST模型所得滞止区换热系数要高于RNG k-ε模型的结果,反之亦然;而在壁面射流区域,RNG k-ε模型对于流场速度的模拟较好,但相应区域的传热模拟并没有表现出明显的优越性.

Numerical simulations of some experiments of slot jet impingement in the literature were carried,in order to investigate the performance of RNG k-ε and Transition SST turbulence models.Distribution of Reynolds-average velocity and turbulent intensity on jet central line,at the jet outlet and in the wall jet region,and the relationship between heat transfer on target wall and the simulated flow field were studied. The results showed that,compared with Transition SST turbulence model,results of RNG k-ε model showed bigger turbulent viscosity and caused the velocity in the jet central line decreased more quickly,which may cause the underestimation of heat transfer on the target wall.And in the impingement region,RNG k-ε model over-estimated the turbulent kinetic energy,which may cause the overestimation of heat transfer on the target wall. Thus,when the Reynolds number of jet is small,the simulated results of heat transfer of the stagnation wall via Transition SST turbulence model would be higher than that via RNG k-ε model,vice versa. In the wall jet region,RNG k-εmodel performed better on the velocity simulation,but didn＇t give better results of heat transfer.