Experimental sensitivity analysis of the global properties of a two-dimensional turbulent wake
Experimental sensitivity analysis of the global properties of a two-dimensional turbulent wake
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DOI：
10.1017/jfm.2011.495
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发表时间：
2012-01
影响因子：
3.7
通讯作者：
V. Parezanović;O. Cadot
中科院分区：
文献类型：
--
作者：
V. Parezanović;O. Cadot
用小圆柱体作为局部扰动，实验研究了‘D’形圆柱体分离流动产生的二维湍流尾迹整体性质的敏感性。主缸的高度为$D=25 mm，控制缸的直径为$d=0。04d$和$d=0。12D$，前者小于脱离主柱的剪切层厚度，后者大于后者。在这两种情况下，控制缸都能够修改全局频率、基本压力和跨向速度关联。结果以敏感度图的形式显示。当控制圆柱体在固定的下游位置沿尾迹垂直移动时，详细分析了雷诺应力、空间结构和回流气泡长度。研究发现，回流气泡长度的增加伴随着雷诺应力的衰减，其空间结构随着基压的增加而向下游移动。可以独立于气泡长度修改来降低或增加全局频率。这些整体性质的敏感性是基于控制圆柱体通过与主要分离的剪切层相互作用来改变Kármán涡街形成区大小的能力来解释的。讨论了相应的物理机制。通过展宽关联，研究了二维控制圆柱对尾迹三维特性的影响。当控制缸被放置在主缸尾迹的回流区内时，这一点被发现是改善的。
Abstract The sensitivity of the global properties of a two-dimensional turbulent wake produced by the separated flow of a ‘D’-shaped cylinder at $\mathit{Re}= 13\hspace{0.167em} 000$ is investigated experimentally using a small circular control cylinder as a local disturbance. The height of the main cylinder is $D= 25~\mathrm{mm} $ and control cylinders are of diameters $d= 0. 04D$ and $d= 0. 12D$, the former being smaller than the shear layer thickness detaching from the main cylinder, while the latter is larger. In both cases, the control cylinder is able to modify the global frequency, base pressure and spanwise velocity correlation. The results are presented as sensitivity maps. Reynolds stresses spatial structure and the recirculation bubble length are examined in detail when the control cylinder is displaced vertically across the wake at a fixed downstream location. It is found that the increase of the recirculation bubble length is accompanied by a damping of Reynolds stresses with a downstream shift of their spatial structures together with the base pressure increase. The global frequency can be either decreased or increased independently of the bubble length modification. The sensitivity of these global properties is interpreted on the basis of the ability of the control cylinder to change the size of the formation region of the Kármán vortex street by interacting with the primary detached shear layers. The corresponding physical mechanisms are discussed. The impact of a two-dimensional control cylinder on the three-dimensional properties of the wake is examined through spanwise correlation. This is found to be improved whenever the control cylinder is placed inside the recirculation region of the main cylinder wake.