颗粒间碰撞对槽道湍流中颗粒聚集效应的影响研究  

STUDY OF THE EFFECTS OF INTER-PARTICLE COLLISIONS ON PARTICLE ACCUMULATION IN TURBULENT CHANNEL FLOWS

作　　者：崔元凯 张欢[1,2,3] Cui Yuankai;Zhang Huan(Center for Particle-Laden Turbulence,Lanzhou University,Lanzhou 730000,China;Key Laboratory of Mechanics on Disaster and Environment in Western China Attached to the Ministry of Education of China,Lanzhou University,Lanzhou 730000,China;College of Civil Engineering and Mechanics,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]兰州大学湍流−颗粒研究中心,兰州730000 [2]兰州大学西部灾害与环境力学教育部重点实验室,兰州730000 [3]兰州大学土木工程与力学学院,兰州730000

出　　处：《力学学报》2024年第2期365-376,共12页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金(92052202);中央高校基本科研业务费(lzujbky-2021-ey19)资助项目。

摘　　要：颗粒两相湍流广泛存在于自然现象和工业流动中,与人们的生活和生产活动息息相关.通常情况下,当颗粒的体积分数小于O(10^(-4))时,颗粒间的碰撞效应被忽略.一些研究发现,在颗粒两相壁湍流中,即使在低体积分数情况下,由于湍泳和倾向性聚集会导致颗粒局部浓度较高,颗粒间的碰撞频繁发生.然而,已有结果大多针对均匀各向同性湍流或采用大涡模拟的研究手段,尚缺少关于颗粒两相槽道湍流的直接数值模拟研究,颗粒间碰撞对颗粒聚集程度和形态影响的定量规律仍不清楚.文章基于欧拉-拉格朗日点颗粒框架,在摩擦雷诺数为Re_(τ)=180的条件下,采用直接数值模拟探讨了有/无颗粒间碰撞时水平槽道湍流中双分散颗粒聚集模式的差异.算例的颗粒平均质量分数为Φm~O(1),因此模型中还考虑了颗粒对流场的反馈作用.研究发现,颗粒间碰撞驱使近壁颗粒向槽道中心迁移,导致颗粒平均浓度的壁法向廓线变得十分平坦,抑制了壁湍流中颗粒的湍泳现象.同时,颗粒间碰撞导致颗粒在与壁面平行的水平薄层内更加均匀地分布.特别是在黏性底层内,各向异性的颗粒条带结构完全消失.这些结果表明,颗粒间碰撞显著抑制了水平槽道湍流中颗粒的湍泳和近壁区的倾向性聚集现象.Particle-laden turbulence is common in natural phenomena and industrial flows,closely related to human life and production activities.In general,when the volume fraction of particles is less thanO(10^(-4)),inter-particle collisions are neglected.Some studies have found that in particle-laden wall turbulence,even at low volume fractions,the effects of turbophoresis and preferential concentration can lead to higher local particle concentrations and frequent particle collisions.However,most existing results focus on homogeneous isotropic turbulence or employ large eddy simulations,and there is a lack of direct numerical simulation studies on particle-laden turbulent channel flows.The quantitative relationship between inter-particle collisions and the degree and morphology of particle clustering remains unclear.In this study,based on the Euler-Lagrangian point-particle framework,at a friction Reynolds number of Re_(τ)=180,we conducted direct numerical simulations to investigate the differences in the accumulation patterns of bidisperse particles in horizontal turbulent channel flows with and without inter-particle collisions.The average mass fraction of particles in the simulations is Φm~O(1),so the feedback of particles on the flow field is also considered in the model.We found that inter-particle collisions drive near-wall particles to migrate towards the center of the channel,resulting in a flattened wall-normal profile of the average particle concentration,which suppresses particle turbophoresis in wall turbulence.Meanwhile,inter-particle collisions lead to a more uniform distribution of particles within a horizontal thin layer parallel to the wall.In particular,within the viscous sublayer,the anisotropic particle streak structures completely disappear.These results indicate that inter-particle collisions significantly suppress particle turbophoresis and near-wall preferential concentration phenomena in horizontal channel turbulence.

关 键 词：颗粒两相湍流 槽道湍流 颗粒聚集 颗粒间碰撞 直接数值模拟 

分 类 号：O359[理学—流体力学]