THE MINIMAL FLOW UNIT IN NEAR-WALL TURBULENCE
THE MINIMAL FLOW UNIT IN NEAR-WALL TURBULENCE
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DOI：
10.1017/s0022112091002033
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发表时间：
1991-04-01
影响因子：
3.7
通讯作者：
MOIN, P
中科院分区：
文献类型：
--
作者：
JIMENEZ, J;MOIN, P
在选择足够小的计算框上以低到低的中等雷诺数对非稳态通道流进行直接数值模拟，以便流由相同结构的双周期（x 和 z）阵列组成。 目标是分离基本流动单元，研究其形态和动力学，并评估其对完全发育的通道中湍流的贡献。 对于沿展向方向宽于约 100 个壁单位的盒子，流动是湍流，并且低阶湍流统计数据与近壁区域的实验非常吻合。 对于低于该阈值的狭窄宽度范围，仅靠近一个壁的流动保持湍流，但当与局部壁应力成比例时，其统计数据仍然与实验数据相当一致。 对于较窄的盒子，仅找到层流解决方案。 在所有情况下，基本盒都包含单个低速条纹，由纵向带组成，在纵向带上薄层展向涡量被提升远离壁。 确定了湍流再生的基本间歇期，并且观察到该过程包括壁层涡量围绕单个倾斜纵向涡旋的包裹。
Direct numerical simulations of unsteady channel flow were performed at low to at low at moderate Reynolds numbers on computational boxes chosen small enough so that the flow consists of a doubly periodic (in x and z) array of identical structures. The goal is to isolate the basic flow unit, to study its morphology and dynamics, and to evaluate its contribution to turbulence in fully developed channels. For boxes wider than approximately 100 wall units in the spanwise direction, the flow is turbulent and the low-order turbulence statistics are in good agreement with experiments in the near-wall region. For a narrow range of widths below that threshold, the flow near only one wall remains turbulent, but it statistics are still in fairly good agreement with experimental data when scaled with the local wall stress. For narrower boxes only laminar solutions are found. In all cases, the elementary box contains a single low-velocity streak, consisting of a longitudinal strip on which a thin layer of spanwise vorticity is lifted away from the wall. A fundamental period of intermittency for the regeneration of turbulence is identified, and that process is observed to consist of the wrapping of the wall-layer vorticity around a single inclined longitudinal vortex.