中文摘要：

采用氢气泡流动显示技术，研究了不同粒径粗糙元对壁湍流拟序结构的影响。实验中粗糙元布置在氢泡丝前，均匀排成一排，基于平均速度和水力直径的雷诺数从14300到48000变化，离散粗糙元直径分别为0．9、1．6、2．3、4、5和6mm，粗糙元间距为2cm。实验发现：光滑壁面和粗糙元壁面近壁湍流条带数量和条带高度都随雷诺数增大而增加。相同雷诺数下，粗糙元壁面流动产生的条带数量和条带高度随粗糙元粒径增大而增加。粗糙元壁面湍流条带数量和条带高度均比光滑壁面大。该研究对壁湍流的流动控制工程应用具有参考价值。

英文摘要：

This paper investigates effects of roughness elements on the near-wall coherent vortex structures using the hydrogen bubble flow visualization technology. The roughness elements row is located on the bottom wall before the hydrogen bubble wire. The Reynolds number, based on the mean velocity and channel hydraulic diameter, is from 14300 to 48000, and the roughness elements are spheres in diameter of 0.9, 1.6, 2.3, 4, 5 and 6 mm arranged at intervals of 2 cm in the spanwise direction. Both the number of low-speed streak and the vortex height increase with the roughness element sizes and with the Reynolds number. The statistical streak number and vortex height in roughness wall flow are both greater than those of smooth wall flow at the same flow Reynolds number. This study is valuable for wall turbulence flow control in engineering.