Large Eddy Simulation of Turbulent Channel Flows over Rough Walls with Stochastic Roughness Height Distributions
Large Eddy Simulation of Turbulent Channel Flows over Rough Walls with Stochastic Roughness Height Distributions
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DOI：
10.1007/s42241-019-0052-y
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发表时间：
2019-06
影响因子：
2.5
通讯作者：
Hao Lu
中科院分区：
文献类型：
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作者：
Hao Lu
本文采用大涡模拟和浸没边界方法研究了具有随机粗糙度分布的三维槽道湍流流动。得到的光滑和粗糙槽道流的平均和脉动速度分布与现有的数值和实验结果吻合良好。在平均粗糙度相同的情况下，随机粗糙度对湍流速度统计和相干结构的影响比均匀粗糙度大。随着粗糙度的增大，平均流速和流向脉动流速减小，展向流速和壁面法向脉动流速增大。此外，人们观察到更大，更丰富的准流向涡，发夹涡和细长结构的波峰平面以上的粗糙度阵列的高度随机粗糙的墙壁的情况下。然而，低速条纹结构被局部破碎，喷射和扫掠事件被平均粗糙度高度以下的随机粗糙度抑制。这项研究的结果支持汤森的壁相似性假设的随机和均匀的粗糙壁湍流，表明在这两种情况下，表面粗糙度对湍流的影响仅限于粗糙的子层。
This paper studies the 3-D turbulent channel flows over rough walls with stochastic roughness height distributions by using the large eddy simulation and the immersed boundary method. The obtained mean and fluctuating velocity profiles for the smooth and rough channel flows agree well with the available numerical and experimental results. The stochastic surface roughness is found to have a more significant influence than the uniform surface roughness on the turbulent velocity statistics and the coherent structures, with the same average roughness height. With a greater variation in the roughness height, the mean velocity and the streamwise fluctuating velocity is decreased and the spanwise velocity and the wall-normal fluctuating velocity are increased. In addition, one observes larger and more profuse quasi-streamwise vortices, hairpin vortices and elongated structures above the crest plane of the roughness array in cases of highly stochastic rough walls. However, the low-speed streaky structures are broken up locally and the ejection and sweep events are depressed by the stochastic roughness below the average roughness height. The results of this study support Townsend’s wall-similarity hypothesis for both stochastic and uniform rough wall turbulences, demonstrating that in both cases the effects of the surface roughness on the turbulent flow are limited to the rough sub-layer.