Examination of a critical roughness height for outer layer similarity
Examination of a critical roughness height for outer layer similarity
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DOI：
10.1063/1.2757708
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发表时间：
2007-09
影响因子：
4.6
通讯作者：
K. Flack;M. Schultz;Jonathan S. Connelly
中科院分区：
文献类型：
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作者：
K. Flack;M. Schultz;Jonathan S. Connelly
研究了光滑和粗糙壁面湍流边界层外层相似的临界粗糙度高度的存在性。结果表明，在Reθ= 7.3×103-13×103条件下，覆盖沙粒和编织网的平板边界层厚度与粗糙度高度之比（δ∕k）在16 ~ 110之间变化。在所有测试的情况下，直接被粗糙度修饰的层（粗糙度子层）被限制在距离壁面<5k或<3ks的区域（其中ks为等效沙粒粗糙度高度）。在粗糙度较大的情况下，紊流修正区域延伸到外部流动。然而，在距离壁面5k或3ks之外，平滑壁面边界层和粗糙壁面边界层之间的湍流量相似。这些结果表明，粗糙度开始影响大部分或全部边界层的临界粗糙度高度不存在。相反，外部流量只是随着增加而逐渐改变…
The existence of a critical roughness height for outer layer similarity between smooth and rough wall turbulent boundary layers is investigated. Results are presented for boundary layer measurements on flat plates covered with sandgrain and woven mesh with the ratio of the boundary layer thickness to roughness height (δ∕k) varying from 16 to 110 at Reθ=7.3×103–13×103. In all cases tested, the layer directly modified by the roughness (the roughness sublayer) is confined to a region <5k or <3ks from the wall (where ks is the equivalent sandgrain roughness height). In the larger roughness cases, this region of turbulence modification extends into the outer flow. However, beyond 5k or 3ks from the wall, similarity in the turbulence quantities is observed between the smooth and rough wall boundary layers. These results indicate that a critical roughness height, where the roughness begins to affect most or all of the boundary layer, does not exist. Instead, the outer flow is only gradually modified with increas...