湍流边界层厚度对三维空腔流动的影响

采用脱体涡模拟(DES)方法开展了不同湍流边界层厚度(TTBL)下的三维空腔非定常流动数值计算。空腔长、宽、深比例为5:1:1,来流马赫数为0.85,雷诺数为13.47×10⁶ m^-1,各工况湍流边界层厚度比值为1:2:4:8。研究结果表明,湍流边界层厚度对自由剪切层的发展、空腔底部静态压力分布、脉动压力及空腔流动类型均有重要影响,且随着边界层厚度的增大,下游剪切层覆盖的范围会增大,但是剪切层增长率降低;空腔前后静态压力压差减小、压力梯度下降;腔内局部测点的脉动压力声压级下降,各阶声压峰值频率向低频方向偏移;空腔流动类型往开式流动方向转换。

Effect of turbulent boundary layer thickness on a three-dimensional cavity flow

Unsteady numerical computation of a three-dimensional cavity with different thicknesses of turbulent boundary layer(TTBL) is conducted using the detached eddy simulation(DES) modeling approach. The rectangular cavity has an aspect ratio of 5:1:1, the Mach number is 0.85 and Reynolds number is 13.47×10⁶ m^-1. Four calculated TTBLs are at the ratio of 1:2:4:8. The results show that TTBL has a significant effect on the evolution of free shear layer, cavity floor pressure distribution, pressure fluctuation and cavity flow type. With the increase of TTBL, the region covered by free shear layer becomes larger but TTBL grows more slowly; the pressure differential between leading edge and trailing edge drops down and pressure gradient along the cavity floor also decreases. Meanwhile, sound pressure level of pressure fluctuation reduces, peaks of tonal modes transfer to lower frequencies and the cavity flow tends to open flow type with thicker turbulent boundary layer.