Modeling And Simulating Of Multiphase Flows Via Lattice Boltzmann Method

Multiphase flows are typical nonlinear, nonequilibrium, multiscale complex systems. The lattice Boltzmann method (LBM), based on nonequilibrium statistical physics, is particularly suitable for modeling and simulating such systems. This paper aims to develop LBM from the following three aspects:physical modeling, numerical scheme and data analysis method, and applies it to investigate behaviors of multiphase flows. The main contents are as below:(i) Based on the fast Fourier transform (FFT) and its inverse, we propose the FFT-TLB model for compressible thermal multiphase flows. With this new model, artificial velocities near interfaces decrease to negligible scale and the numerical total energy is better conserved;(ii) Investigate thermal and isothermal symmetric liquid-vapor separations via the FFT-TLB model. To effectively characterize and pick up information from such a complex system. Minkowski functionals are employed to characterize the density fields, as well as to understand the configurations and the kinetic processes;(iii) Via the FFT-TLB model, we study the effects of heat conduction, viscosity and Prandtl number on thermal liquid-vapor separation quantitatively:(iv) Propose a D2V19-LB model for compressible fluids. Via this model, we investigate the Kelvin-Helmholtz instability, specially examine the velocity and density gradient effects;(v) Based on the original D2V65-LB model, by modifying the BGK collision operator, we propose a flux-limiter-LB model for compressible flows with flexible specific-heat ratio and Prandtl number. The above-mentioned works help to extend the LBM to study multiphase and compressible flows, and provide physical supports for related engineering applications.