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Homogenization of streaks in a laminar boundary layer
Experiments in Fluids ( IF 2.4 ) Pub Date : 2020-04-27 , DOI: 10.1007/s00348-020-02947-1
Dominik K. Puckert , Yongxiang Wu , Ulrich Rist

Abstract The present work, based on experimental, numerical and theoretical investigations, introduces a method to homogenize streaks in the laminar boundary layer. The streaks are created by a spanwise array of roughness elements on the surface of a flat plate. A homogenization body in the form of a horizontal bar is added at a downstream location away from the roughness array to homogenize the velocity differences of the streaks in the laminar boundary layer. Measurements are done with hot-film anemometry and supported by numerical simulations and linear stability theory. The streak amplitude can be significantly reduced with the proposed homogenization body. Furthermore, the reduction in spanwise gradients of the mean velocity leads to a significant reduction in the sinuous instability of the streaky flow. The effects of the homogenization body on the displacement thickness and the observation of flow unsteadiness downstream of the homogenization body are discussed. The present work thus proposes and explores a passive technique to control undesired streaks in the laminar boundary layer. Graphic abstract

中文翻译:

层流边界层中条纹的均匀化

摘要 目前的工作基于实验、数值和理论研究,介绍了一种使层流边界层中的条纹均匀的方法。条纹是由平板表面上的粗糙度元素的展向阵列产生的。在远离粗糙度阵列的下游位置添加水平杆形式的均质体,以均质层流边界层中条纹的速度差异。测量是通过热膜风速测量完成的,并得到数值模拟和线性稳定性理论的支持。使用建议的均质体可以显着降低条纹幅度。此外,平均速度的展向梯度的降低导致条纹流的蜿蜒不稳定性显着降低。讨论了均质体对位移厚度的影响以及均质体下游流动不稳定性的观察。因此,目前的工作提出并探索了一种被动技术来控制层流边界层中不需要的条纹。图形摘要
更新日期:2020-04-27
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