平板湍流边界层微气泡减阻的大涡模拟  

LES Study of Microbubble Drag Reduction on Flat-plate Turbulent Boundary Layers

作　　者：冯岩岩 李振林[1] 姬忠礼[1] FENG Yan-yan;LI Zhen-lin;JI Zhong-li(College of Mechanical and Transportation Engineering, China University of Petroleum, Beijing 102249, China)

机构地区：[1]中国石油大学(北京)机械与储运工程学院,北京102249

出　　处：《节能技术》2021年第4期305-311,331,共8页Energy Conservation Technology

基　　金：第65批中国博士后科学基金面上资助(2019M651285);中国石油大学(北京)科研基金资助(2462021YJRC005)。

摘　　要：采用大涡模拟研究了通入微气泡对光滑平板及部分粗糙平板湍流边界层减阻的影响。在计算域进口引入扰动以在较短距离内生成雷诺数(基于边界层动量厚度)为1430的平板湍流边界层。利用Weierstrass-Mandelbrot分形函数生成算术平均粗糙高度为75μm的粗糙表面轮廓曲线。结果表明,微气泡体积分数增大时,作用在微气泡上的浮力较大,导致拟序结构远离壁面,并且边界层内部动量交换强度降低,摩擦阻力降低明显;无微气泡时,粗糙表面的存在使得其下游速度条带数量减少,尺寸有所增加,其壁面摩擦系数小于光滑平板情况;在相同的通入微气泡体积分数下,部分粗糙平板上的减阻量小于光滑表面,一方面是由于部分粗糙表面平板本身的摩擦阻力系数较小,另一方面是粗糙表面吸附了一部分微气泡,减弱了微气泡的减阻效果。Microbubble injection effects on drag reduction of turbulent boundary layers over a smooth flat-plate and a partial-roughed flat-plate are studied using large-eddy simulation.The turbulent boundary layer with a Reynolds number(based on the momentum thickness of the turbulent boundary layer)of 1430 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 75μm.Results show that when the microbubble volume fraction increases,buoyancy acting on microbubbles is larger,resulting in the coherent structure migrating away from the wall,the reduced momentum exchange inside the turbulent boundary layer and the frictional drag is reduced significantly.Without microbubbles,the presence of rough surface reduces the downstream number of velocity streaks and increases their size,and the frictional coefficient is smaller than the smooth plate.With the same microbubble volume fraction at inlet,the amount of drag reduction for the partial-roughed flat-plate case is less than the smooth surface case.On the one hand,it is due to the smaller frictional drag coefficient of the partial-rough surface without microbubbles.On the other hand,the rough surface adsorbs microbubbles as they passing by,weakening the microbubble effect on drag reduction.

关 键 词：微气泡 湍流边界层 减阻 粗糙表面 大涡模拟 

分 类 号：O359[理学—流体力学]