第 卷 总第 期 节 能 技 术
39 ꎬ 228 « » nolds number (based on the momentum thickness of the turbulent boundary lay ̄
er) of 1 430 is generated within a short distance of inflow by introducing disturbances. Weierstrass -
Mandelbrot fractal function is used to generate a rough surface profile curve with an arithmetic mean
roughness height of 75 μm. Results show that when the microbubble volume fraction increasesꎬ buoyancy
acting on microbubbles is largerꎬ resulting in the coherent structure migrating away from the wallꎬ the re ̄
duced momentum exchange inside the turbulent boundary layer and the frictional drag is reduced signifi ̄
cantly. Without microbubblesꎬ the presence of rough surface reduces the downstream number of velocity
streaks and increases their sizeꎬ and the frictional coefficient is smaller than the smooth plate. With the
same microbubble volume fraction at inletꎬ the amount of drag reduction for the partial - roughed flat -
plate case is less than the smooth surface case. On the one handꎬ it is due to the smaller frictional drag
收稿日期 修订稿日期
2020 - 12 - 20 2021 - 01 - 12
基金项目:第 批中国博士后科学基金面上资助 中国石油大学 北京 科研基金资助
65 (2019M651285)ꎻ ( ) (24
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