三维边界层的湍流特性及其二阶矩模拟

根据现有实验数据,本文进一步分析了三维边界层内纵向涡对雷诺应力分布的影响,从而建立了一个足以模拟三维边界层湍流特性的二阶矩封闭模式。在新模式中,着重考虑了三维平均涡场引起的雷诺应力输运的非线性作用。以文3]给出的模拟无限后掠翼实验为例,本文分别应用基准的二阶矩模式和新建立的非线性二阶矩模式对三维边界层内的雷诺应力分布作了数值预计。结果表明:应用基准二阶矩模式所得雷诺应力诸分量的预计值均比相应的测量值大得多,且完全不能预计切应力方向相对于速度梯度方向的滞后;而非线性二阶矩模式对雷诺应力分布的预计则基本上与测量数据符合,且能定性地模拟切应力方向相对于速度梯度方向的滞后。

Turbulence Behaviour in Three-Dimensional Boundary Layers and Its Second-Moment Modelling

An investigation of the effects of longitudinal mean vortic-ity on the Reynolds-stress distribution in a pressure-driven 3D boundary layer is made based on the existing experimental data. A refined second-moment closure is adopted for modelling the main features of the 3D turbulent boundary layer. In setting up the new closure, the attention is paid mainly to capturing the nonlinear effects of a 3D mean vorticity field on the Reynolds-stress development and the increase in dissipation rate of turbulence energy due to vortex stretching, Bradshaw and Pontikos' experiment3] simulating the flow past an infinite swept wing is taken as the test case for the basic and the refined nonlinear second-moment closures. Computational results show that the prediction of the basic closure greatly overestimates the magnitude of every component of the reynolds-stress tensor giving no deviation of the direction of shear-stress vector from that of velocity-gradient vector, whereas the corresponding prediction of the refined nonlinear . closure is quite agreeable with the experimental data qualitatively reproducing the lag of the shear-stress direction behind the velocity-gradient direction.