(369m) Comparison of Finite Volume and Lattice Boltzmann Methods for Simulations of Multicomponent Flows

Pseudopotential lattice Boltzmann (LB) methods are often employed to study multiphase flow phenomena, such as droplet deformation, breakup, and coalescence as well as emulsion flows in porous media. In a common model for binary mixtures of ideal components, a repulsive force between the components is used to induce phase separation and apply interfacial tension. This talk will compare the computational efficiency of this LB method against an equivalent finite volume (FV) solver. This FV code solves the same macroscopic-scale equations as the LB model for a binary system in a two dimensional domain. The FV implementation replicates the phase separation of the LB model. Differences in the interfacial tension between the phases are due to truncation of the Taylor series expansion of the LB interaction force that is used in the FV version. While the FV approach allows faster updates of the domain for every timestep, a smaller timestep is required to ensure stability, which negates the improvement in simulation speed. The FV implementation, however, allows independent variation of model parameters, which is not possible in LB. For example, the viscosity can be changed without affecting interfacial tension or the extent of phase separation. Furthermore, arbitrarily low interfacial tensions can be obtained in the FV formulation without suppressing phase separation. The significance of the diffusion rate of the components on the deformation of a droplet in shear will also be demonstrated.

Droplet breakup computed with the FV implementation of the two-component LB model.