耦合流体体积和水平集方法的自由面流动格子Boltzmann模型  

Coupled volume-of-fluid and level-set lattice Boltzmann method for free surface flows

作　　者：刘翔 童自翔 汪思成 何雅玲 LIU Xiang;TONG ZiXiang;WANG SiCheng;HE YaLing(Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education,School of Energy and Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学能源与动力工程学院,热流科学与工程教育部重点实验室,西安710049

出　　处：《中国科学：技术科学》2024年第11期2095-2106,共12页Scientia Sinica(Technologica)

基　　金：国家自然科学基金“双碳”专项(批准号:52341601)资助项目。

摘　　要：作为实际工程应用中重要的两相流问题,自由面流动具有两相密度比大、Reynolds数(Re)高和相界面(自由面)拓扑变化复杂等特点.为实现该类流动问题的数值预测,需准确捕捉/追踪自由面位置.本文发展了一种耦合流体体积(volume-of-fluid, VOF)和水平集(level-set, LS)方法的自由面流动格子Boltzmann(lattice Boltzmann, LB)模型.在该模型中,针对传统自由面流动模拟中存在的压缩性影响与稳定性限制,采用多松弛时间(multiple relaxation time, MRT)不可压缩LB模型对流场进行求解.基于VOF的思想,引入流体体积分数表征自由面信息,通过介观不可压速度分布函数的迁移过程实现自由面流体体积分数的更新与界面演化,避免了传统VOF方法的复杂界面推进与更新过程.为准确求解自由面几何信息,通过界面重构的方法将流体体积分数转换为LS函数并计算界面法向量和曲率,减少了相较于采用高阶格式求解LS方程带来的计算量,且与采用VOF方法计算相比,具有更高的计算精度.最后通过溃坝问题和液滴撞击薄液膜等典型算例证明了所发展模型的准确性.该模型为自由面流动问题提供了一种新的求解思路.As a representative two-phase flow problem in practical engineering applications, the free surface flow is often characterized by ahigh two-phase density ratio, high Reynolds number (Re), and a complex topological change of the phase interface (free surface). Tonumerically simulate a free surface flow, it is necessary to accurately capture/track the location of the free surface. In this work, alattice Boltzmann (LB) model coupled with the volume-of-fluid (VOF) and level-set (LS) method is developed for free surface flows.To reduce the compressibility error and limited stability of the standard LB method, the incompressible LB model with the multiplerelaxation-timecollision term is used to solve the flow field. Based on the idea of VOF, mass streaming and interface evolution of freesurface are performed through the streaming process of mesoscopic incompressible distribution functions. The complex interfaceadvancing and updating process of the traditional VOF method is avoided. To accurately solve the geometric information of a freesurface, the interface reconstruction method is used to convert the fluid volume fraction into the LS function. The normal vector andcurvature of the interface are calculated using the reconstructed LS function. Through this treatment, computational efficiency can beimproved compared with solving the LS equation directly based on a higher-order numerical scheme. Further, a higher numericalaccuracy can be obtained for the geometric information of the free surface compared with the VOF method. Finally, the accuracy ofthe developed model is validated using benchmarks such as the dam break problem and droplet impacting the thin liquid film process.Therefore, the proposed model provides a new strategy to solve free surface flows.

关 键 词：自由面流动 不可压缩格子Boltzmann模型 流体体积 水平集 

分 类 号：O35[理学—流体力学]