采用氢气泡流动显示技术，研究了壁面不同排列粗糙元对近壁湍流拟序结构的影响。实验中基于平均速度和水力直径的雷诺数分别为14300、31200、48000。氢泡丝上游布置的离散粗糙元直径为2．3、4和6mm，得到了光滑壁面和5种不同排列方式的离散粗糙元壁面湍流条带和湍流斑块特征。结果发现：相同雷诺数和相同排列方式下条带间距随着粗糙元直径增大而减小，条带或湍流斑块高度随粗糙元直径的增大而增大。对于不同粗糙元排列方式，当展向间距为0、流向间距为粗糙元直径4倍时，条带消失，出现大量混乱的湍流斑块，且此时湍流斑块高度最大，表明此种排列方式对壁湍流拟序结构影响最大。布有粗糙元时条带间距均比光滑壁面小，条带或湍流斑块高度均比光滑壁面大。该研究对于壁湍流控制的工程应用具有指导意义。
This paper investigates effects of roughness element arrangements on near-wall coherent vortex structures using hydrogen bubble fiow visualization technology. The flow Reynolds number, based on the mean flow velocity and channel hydraulic diameter, is 14300, 31200 or 48000. Roughness elements are arranged upstream before the bubble wire in five different ways. Their diameter is 2.3, 4, or 6 mm. The morphological characteristics of near-wall turbulence streaks and turbulence spots are obtained. The streak spacing for each arrangement decreases with increasing of roughness element diameter in the condition of the same Reynolds number but the height of streaks or turbulence spots are exactly inverse. The streaks disappear and the highest spots are observed when the streamwise interval of roughness elements is specified as 4d and the spanwise interval is 0. This kind of arrangement of roughness elements has the strongest influence on coherent structures. The study is valuable for the near-wall flow control in engineering applications.
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