湍流边界层近壁区马蹄涡拟序结构的数值模拟与分析

采用大涡模拟对低雷诺数槽道湍流进行了数值模拟,进口边界条件采用了给定扰动波方法,经过短过渡段得到完全发展湍流.计算中采用了动态亚格子模型和预处理技术,进口采用的动量厚度雷诺数是670.大涡模拟对计算得到的平均速度剖面以及脉动分量与DNS解进行对比,验证了计算结果的可靠性.计算结果显示了湍流场中马蹄涡的形成及演化过程,其中包括形成单腿马蹄涡和形成对称涡腿的马蹄涡,同时发现流场中存在由亚谐波引起的拟序结构的交错现象,并在此基础上分析了湍流边界层近壁区马蹄涡结构的演化.

NUMERICAL SIMULATION AND ANALYSIS OF HORSESHOE-SHAPED VORTEX IN NEAR-WALL REGION OF TURBULENT BOUNDARY LAYER

The low-Reynolds-number full developed turbulent flow in channels is simulated using large eddy simulation (LES) method with the preconditioned algorithm and the dynamic subgrid-scale model, with a given disturbance in inlet boundary, after a short development section. The inlet Reynolds number based on momentum thickness is 670. The computed results show good agreement with direct numerical simulation (DNS), which include root mean square fluctuated velocity distribution and average velocity distribution. It is also found that the staggered phenomenon of the coherent structures is caused by sub-harmonic. The results clearly show the formation and evolution of horseshoe vortex in the turbulent boundary layer, including horseshoe vortex structure with a pair of streamwise vortexes and one-side leg of horseshoe vortex. Based on the results, the development of the horseshoe-shaped coherent structures is analyzed in turbulent boundary layer.