Direct simulations of a rough-wall channel flow
Direct simulations of a rough-wall channel flow
复制标题
粗糙壁通道流动的直接模拟
DOI：
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发表时间：
2007
影响因子：
3.7
通讯作者：
P. Durbin
中科院分区：
文献类型：
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作者：
Tomoaki Ikeda;P. Durbin
在这项研究中，我们进行了模拟的湍流超过矩形肋横向安装在一个平面的一侧的通道，与另一侧是光滑的。肋之间的间隔足够大，以避免在间隔中形成稳定的涡流，其表现出k型或砂粒粗糙度。根据光滑壁摩擦速度和通道半宽，我们代表性的直接数值模拟案例的雷诺数Reτ为460。根据粗糙壁摩擦速度，粗糙度高度h估计为110个壁单位。速度剖面和动能收支证实了在y = 2h处存在平衡对数层。然而，在粗糙子层，观察到一个显着的湍流能通量。在粗糙面上方的不规则运动形成了一个高能区。涡流条纹的可视化，中断在所有三个方向上的粗糙度子层，表明沙粒粗糙度的三维流动结构复制的二维粗糙度，这种涡流结构是负责高能量的生产。光滑壁和粗糙壁层之间湍流结构的差异也可以在其他流动特性中看到，例如各向异性和湍流长度尺度。
In this study, we performed simulations of turbulent flow over rectangular ribs transversely mounted on one side of a plane in a channel, with the other side being smooth. The separation between ribs is large enough to avoid forming stable vortices in the spacing, which exhibits k-type, or sand-grain roughness. The Reynolds number Reτ of our representative direct numerical simulation case is 460 based on the smooth-wall friction velocity and the channel half-width. The roughness height h is estimated as 110 wall units based on the rough-wall friction velocity. The velocity profile and kinetic energy budget verify the presence of an equilibrium, logarithmic layer at y≳2h. In the roughness sublayer, however, a significant turbulent energy flux was observed. A high-energy region is formed by the irregular motions just above the roughness. Visualizations of vortical streaks, disrupted in all three directions in the roughness sublayer, indicate that the three-dimensional flow structure of sand-grain roughness is replicated by the two-dimensional roughness, and that this vortical structure is responsible for the high energy production. The difference in turbulence structure between smooth- and rough-wall layers can also be seen in other flow properties, such as anisotropy and turbulence length scales.