Parametric forcing approach to rough-wall turbulent channel flow
Parametric forcing approach to rough-wall turbulent channel flow
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DOI：
10.1017/jfm.2012.408
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发表时间：
2012-09
影响因子：
3.7
通讯作者：
A. Busse;N. Sandham
中科院分区：
文献类型：
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作者：
A. Busse;N. Sandham
摘要在Navier-Stokes方程中引入附加力项，模拟了粗糙表面对槽道湍流的影响。该力项包含两个参数，与粗糙度元件的密度和高度相关，以及形状函数，其调节力项相对于与通道壁的距离的影响。这允许比单一参数（例如等效砂粒粗糙度）更灵活地指定粗糙表面。通过直接数值模拟，研究了粗糙力项对槽道湍流的影响。它可以涵盖粗糙流的全部范围，从水力光滑到过渡粗糙到完全粗糙的情况。通过使用不同的参数组合和形状函数，可以匹配不同类型粗糙表面的效果。平均流量和标准湍流统计已被用来比较最近的实验和数值研究的结果，并已发现一个很好的定性agreement. Outer标度被保存的流向速度的平均轮廓，以及在所有，但非常粗糙的情况下，其均方波动。湍流的结构显示出在粗糙层内更各向同性的湍流状态的趋势。在非常粗糙的情况下，展向结构出现在壁面附近，湍流状态类似于混合层。与Ashrafian、Andersson和Manhart的研究（Intl J. Heat Fluid Flow，第25卷，2004年，第100页）的直接比较。373-383）显示了除粗糙壁附近以外的所有地方的平均流和雷诺应力的良好定量一致性。建议的粗糙度力项可能是有益的壁模型直接和大涡数值模拟的情况下，在粗糙壁的流动的确切细节可以忽略不计。
Abstract The effects of rough surfaces on turbulent channel flow are modelled by an extra force term in the Navier–Stokes equations. This force term contains two parameters, related to the density and the height of the roughness elements, and a shape function, which regulates the influence of the force term with respect to the distance from the channel wall. This permits a more flexible specification of a rough surface than a single parameter such as the equivalent sand grain roughness. The effects of the roughness force term on turbulent channel flow have been investigated for a large number of parameter combinations and several shape functions by direct numerical simulations. It is possible to cover the full spectrum of rough flows ranging from hydraulically smooth through transitionally rough to fully rough cases. By using different parameter combinations and shape functions, it is possible to match the effects of different types of rough surfaces. Mean flow and standard turbulence statistics have been used to compare the results to recent experimental and numerical studies and a good qualitative agreement has been found. Outer scaling is preserved for the streamwise velocity for both the mean profile as well as its mean square fluctuations in all but extremely rough cases. The structure of the turbulent flow shows a trend towards more isotropic turbulent states within the roughness layer. In extremely rough cases, spanwise structures emerge near the wall and the turbulent state resembles a mixing layer. A direct comparison with the study of Ashrafian, Andersson & Manhart (Intl J. Heat Fluid Flow, vol. 25, 2004, pp. 373–383) shows a good quantitative agreement of the mean flow and Reynolds stresses everywhere except in the immediate vicinity of the rough wall. The proposed roughness force term may be of benefit as a wall model for direct and large-eddy numerical simulations in cases where the exact details of the flow over a rough wall can be neglected.