耦合流体体积和水平集方法的自由面流动格子Boltzmann模型

As a representative two-phase flow problem in practical engineering applications, the free surface flow is often characterized by a high two-phase density ratio, high Reynolds number (Re), and a complex topological change of the phase interface (free surface). To numerically simulate a free surface flow, it is necessary to accurately capture/track the location of the free surface. In this work, a lattice 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 multiple-relaxation-time collision term is used to solve the flow field. Based on the idea of VOF, mass streaming and interface evolution of free surface are performed through the streaming process of mesoscopic incompressible distribution functions. The complex interface advancing and updating process of the traditional VOF method is avoided. To accurately solve the geometric information of a free surface, the interface reconstruction method is used to convert the fluid volume fraction into the LS function. The normal vector and curvature of the interface are calculated using the reconstructed LS function. Through this treatment, computational efficiency can be improved compared with solving the LS equation directly based on a higher-order numerical scheme. Further, a higher numerical accuracy can be obtained for the geometric information of the free surface compared with the VOF method. Finally, the accuracy of the 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.