| This thesis presents results for two-phase flows with fluid-fluid interfaces that were obtained with two lattice Boltzmann methods. A goal of the study was to determine the ability of these methods to provide reliable simulations of flows with fluid-fluid interfaces. Results for deformation and breakup of drops, coalescence of drops, liquid-liquid-solid contact lines, surface tension driven morphology changes in polymer blends, and surfactant effects were obtained and evaluated.; Of the two methods that were considered, the thermodynamically based "Oxford" method was found to be the more useful method. However, when a free energy model is incorporated in a lattice Boltzmann method program, the results are often at odds with the underlying thermodynamic models. For example, the theoretical surface tension may be substantially different from the value computed from the Laplace pressure. Also, the computed surface tension displays a dependence on the viscosities of the two phases. In spite of this, it will be argued that the LBM simulations can produce useful results provided that they are properly interpreted and applied. In some instances, the results of LBM simulations are more suited to "mesoscopic" fluid objects that have submicron sizes. Prospects for developing new versions of the LBM that can handle large density ratios are discussed. |
