Influence of Ridge Spacing, Ridge Width, and Reynolds Number on Secondary Currents in Turbulent Channel Flow Over Triangular Ridges
Influence of Ridge Spacing, Ridge Width, and Reynolds Number on Secondary Currents in Turbulent Channel Flow Over Triangular Ridges
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脊间距、脊宽度和雷诺数对三角形脊上湍流通道流二次流的影响
DOI：
10.1007/s10494-023-00488-1
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Zhdanov O
中科院分区：
文献类型：
--
作者：
Zhdanov O
对沿流向排列的脊线上的二次流(SC)的研究大多是在矩形脊形断面上进行的。本文采用槽道湍流直接数值模拟的方法，系统地研究了三角脊上方的二次流。在两个摩擦雷诺数550和1000下，研究了脊线间距对流动拓扑、平均流动和湍流统计特性的影响。此外，还探讨了脊线宽度对SCS的影响，这是以前没有考虑到的这种脊形。SCs对剪应力统计量的影响随着槽脊间距的增加而增加，直到SCs填满整个通道。主要结果之一是，对于具有明显二次流的山脊构型，剪应力统计数据表现出明显的雷诺数敏感性，色散剪应力水平随着雷诺数的增加而显著增加。与矩形坎相比，在试验的坎宽范围内，没有观测到坎上的三次流。SCS的流动显示显示，在横向脊面和光滑壁面的交叉处存在角涡。研究发现，随着脊线宽度的增加，这些变化逐渐消失。流向速度波动的预乘频谱显示出对跨距采样位置的强烈依赖性。虽然跨向平均频谱没有显示出SCS的强烈修改，但在与二次电流中心对应的跨向位置采样的频谱在较高波长下出现了显著的能级增加。
Most studies of secondary currents (SCs) over streamwise aligned ridges have been performed for rectangular ridge cross-sections. In this study, secondary currents above triangular ridges are systematically studied using direct numerical simulations of turbulent channel flow. The influence of ridge spacing on flow topology, mean flow, and turbulence statistics is investigated at two friction Reynolds numbers, 550 and 1000. In addition, the effects of ridge width on SCs, which have not previously been considered for this ridge shape, are explored. The influence of SCs on shear stress statistics increases with increased ridge spacing until SCs fill the entire channel. One of the primary findings is that, for ridge configurations with pronounced secondary currents, shear stress statistics exhibit clear Reynolds number sensitivity with a significant growth of dispersive shear stress levels with Reynolds number. In contrast to rectangular ridges, no above-ridge tertiary flows are observed for the tested range of ridge widths. Flow visualisations of SCs reveal the existence of corner vortices that form at the intersection of the lateral ridge sides and the smooth-wall sections. These are found to gradually disappear as ridges increase in width. Premultiplied spectra of streamwise velocity fluctuations show strong dependency on the spanwise sampling location. Whereas spanwise averaged spectra show no strong modifications by SCs, a significant increase of energy levels emerges at higher wavelengths for spectra sampled at the spanwise locations that correspond to the centres of the secondary currents.
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