Dynamical Roles of Large-Scale Structures in Turbulent Channel Flow
Dynamical Roles of Large-Scale Structures in Turbulent Channel Flow
复制标题
DOI：
--
复制
发表时间：
2004
期刊：
影响因子：
3.8
通讯作者：
K. Iwamoto;N. Kasagi;Yuji Suzuki
中科院分区：
文献类型：
--
作者：
K. Iwamoto;N. Kasagi;Yuji Suzuki
为了研究近壁准流向涡与大尺度外层结构之间的关系，对Reτ1160点的槽道湍流流动进行了直接数值模拟。在地球模拟器上使用512个CPU和600 GB内存，总网格点数约为20亿，有效计算速度约为1.4TFLOPS。可视化的流场和湍流统计表明，与低雷诺数流动一样，近壁准流向涡位于低速和高速条状结构之间。另一方面，在远离壁面的地方形成了大尺度的低速/高速区，而小尺度的旋涡则优先聚集在低速区。条状结构仅存在于墙体附近(Y30)，而大型结构则存在于航道中心至近壁区(Y30)，跨距约为100个墙体单元。大尺度结构对雷诺应力的贡献比外层小尺度涡团的贡献大，从而支持了湍流动能的产生。研究还发现，在低速大尺度结构的平流作用下，小尺度涡旋并不是自主聚集，而是聚集在一起。
Direct numerical simulation of a turbulent channel flow at Reτ 1160 was made in order to examine the relationship between the near-wall quasi-streamwise vortices and the large-scale outer-layer structures. The number of the total grid points is about 2 billions, and the effective computational speed is about 1.4 TFLOPS by using 512 CPUs and 600 GB main memory on the Earth Simulator. The visualized flow field and the turbulent statistics suggest that the near-wall quasi-streamwise vortices are located between lowand high-speed streaky structures as those in low Reynolds number flows. On the other hand, the large-scale low/high-speed regions are formed away from the wall, and the small-scale vortices are clustered preferably in the low-speed regions. The streaky structures, of which spanwise spacing is about 100 wall units, exist only near the wall (y 30), while the large-scale structures exist from the center of the channel to the near-wall region (y 30). The large-scale structures have larger contribution to the Reynolds stress than that of clusters of small-scale vortices in the outer layer, so that they sustain the production of turbulent kinetic energy by themselves. It is also found that the small-scale vortices do not agglomerate autonomously, but become clustered with the advective effect of the low-speed large-scale structures.