Transitional flow in the wake of a moderate to large height cylindrical roughness element
Transitional flow in the wake of a moderate to large height cylindrical roughness element
复制标题
中等至大高度圆柱形粗糙度单元后的过渡流
DOI：
10.1007/s00348-015-2069-5
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发表时间：
2015
影响因子：
2.4
通讯作者：
Krämer
中科院分区：
文献类型：
--
作者：
Plogmann;Krämer
本文用粒子图像测速和热线风速仪研究了孤立的圆柱形粗糙度对翼型边界层稳定性的影响。所调查的粗糙度元素的范围从一个亚临界到一个超临界行为方面的临界粗糙度雷诺数。对于亚临界情况，近尾流中的非线性扰动增长由斜Tollmien-Schlichting（TS）型模式控制。然而，在更远的下游，这些扰动模式随着平均流稳定而衰减，并且在远尾流中没有主导模式。相比之下，在过渡构型中，扰动增长增加，但仍与低展弦比（高径比）单元近尾流中心线区域的TS型不稳定性有关。也就是说，中心线区域的扰动表现出与二维单元相似的特性，而在展向外部区域，则发现了Kelvin-Helmholtz（KH）型剪切层不稳定性，这与以前报道的大展弦比孤立单元的情况相同。随着高度的增加，从而，粗糙度的纵横比，KH型不稳定域向中心线延伸，因此，TS型不稳定域减少。对于高的超临界情况下，过渡已经触发在壁面法线和展向剪切层上游和周围的粗糙度。在直接尾流中，周期性剪切层扰动卷起成孤立单元特征的旋涡脱落，这在较低粗糙度雷诺数情况下不存在，这是由于纵横比减小，从而不同的不稳定机制。
The effect of an isolated, cylindrical roughness on the stability of an airfoil boundary layer has been studied based on particle image velocimetry and hot-wire anemometry. The investigated roughness elements range from a sub-critical to a super-critical behavior with regard to the critical roughness Reynolds number. For the sub-critical case, the nonlinear disturbance growth in the near wake is governed by oblique Tollmien–Schlichting (TS) type modes. Further downstream, these disturbance modes are, however, damped with the mean flow stabilization and no dominant modes persist in the far wake. By contrast, in the transitional configuration the disturbance growth is increased, but still associated with a TS-type instability in the near-wake centerline region of the low-aspect (height-to-diameter) ratio element. That is, the disturbances in the centerline region show a similar behavior as known for 2D elements, whereas in the outer spanwise domain a Kelvin–Helmholtz (KH) type, shear-layer instability is found, as previously reported for larger aspect ratio isolated elements. With increasing height and, thereby, aspect ratio of the roughness, the KH-type instability domain extends toward the centerline and, accordingly, the TS-type instability domain decreases. For high super-critical cases, transition is already triggered in the wall-normal and spanwise shear layers upstream and around the roughness. In the immediate wake, periodic shear-layer disturbances roll up into a—for isolated elements characteristic—shedding of vortices, which was not present at the lower roughness Reynolds number cases due to the decreased aspect ratio and, thereby, different instability mechanism.
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影响因子：
3.7
作者：
J. Watmuff
通讯作者：
J. Watmuff
影响因子：
2.4
作者：
B. Wieneke
通讯作者：
B. Wieneke
球面粗糙度元引起的边界层转变的烟雾观察
影响因子：
1.7
作者：
M. Mochizuki
通讯作者：
M. Mochizuki
影响因子：
2
作者：
S. Roberts;M. Yaras
通讯作者：
S. Roberts;M. Yaras
DOI：
10.2514/6.2014-2886
发表时间：
2014-06
期刊：
--
影响因子：
--
作者：
B. Plogmann;W. Wuerz;E. Kraemer
通讯作者：
B. Plogmann;W. Wuerz;E. Kraemer