近壁湍流中微小非球形颗粒取向行为研究综述  

Reviews on alignment of non-spherical particles in wall-bounded turbulence

作　　者：崔智文 赵立豪 CUI Zhiwen;ZHAO Lihao(Department of Engineering Mechanics,School of Aerospace Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学航天航空学院工程力学系,北京100084

出　　处：《空气动力学学报》2021年第3期99-108,I0003,共11页Acta Aerodynamica Sinica

基　　金：国家自然科学基金(11911530141,11702158)。

摘　　要：本文回顾了近十年关于微小非球形颗粒在壁湍流中取向行为的数值研究进展,重点介绍了数值方法和物理机理方面的发现。由于壁面的存在,在近壁面区域存在较强的平均剪切以及复杂的湍流结构,使得壁面的湍流具有较强的各向异性特点。前期研究发现杆状颗粒在壁面附近会倾向性地朝着流向方向,而碟状颗粒会倾向于朝着壁面法向,且这种倾向性取向行为会随着颗粒形状偏离球形的程度的增加而增强。同时,研究发现颗粒的倾向性取向行为与流体的拉格朗日的拉伸与压缩方向具有较强相关性。但是,颗粒的取向与流体的拉格朗日的拉伸与压缩方向在壁面附近的相关性要弱于其在远离壁面的槽道中部或均匀各向同性湍流的相关性,且存在较明显的形状敏感性。前期工作以杆状颗粒为例分析了其相对于拉格朗日坐标系(由左柯西格林张量三个主轴方向确定)的概率密度分布的特点,并进一步阐释颗粒行为与拉格朗日的拉伸与压缩方向的差异。同时,基于壁面湍流的特点,建立了以平均剪切与速度梯度脉动之比的颗粒转动周期预测的二维简化模型,并进一步揭示了平均剪切与速度梯度脉动在颗粒取向行为趋近于拉格朗日拉伸与压缩方向过程中的重要作用。The article reviews recent progress on the orientation dynamics of non-spherical particles in wallbounded turbulence,focusing on the numerical methods and physical mechanisms.Due to the presence of solid wall,there is a strong mean shear and near-wall turbulence structures,which lead to anisotropy of wall-bounded turbulence.In previous studies,the prolate particles are found to preferentially align in the streamwise direction while the oblate ones preferentially orient to the wall-normal direction in the vicinity of the wall.The preferential alignments of particles are enhanced with increasing asphericity of particles.In addition,the orientations of the particles have a strong correlation with the directions of Lagrangian fluid stretching and compression.Nevertheless,the correlation between the particle orientation and the Lagrangian stretching and compression near the wall is weaker than that in the core region of the channel or in homogeneous isotropic turbulence.To better understand this observation,prolate particles are investigated to analyze their probability distribution relative to the Lagrangian coordinate frame,which is defined by the three principle axes of the left Cauchy-Green tensor.A two-dimensional model for predicting the particle rotation period was developed based on the ratio of mean shear to the fluctuations of fluid velocity gradient tensor according to the characteristics of wall-bounded turbulence.The model revealed that this ratio plays an important role in the alignments of non-spherical particles relative to the directions of Lagrangian stretching and compression in the shear turbulence.

关 键 词：非球形颗粒 壁湍流 颗粒取向 拉格朗日拉伸与压缩方向 直接数值模拟 

分 类 号：O357.5[理学—流体力学]