Lattice Boltzmann simulation of multiphase flows

In many technical applications and natural occurrence of multiphase flows are of great importance. Among the phenomena studied in this project are the transport of discrete solid particles in liquids or gases. Prominent examples are suspensions of small nanoscale particles in liquids and possibly in gases (dust) or the transport of granular materials such as in water. Depending on their size, the motion of the particles by thermal fluctuations (Brownian motion) or dominated by viscous interaction with the surrounding fluid. Depending on the volume fraction of particles, the rheological properties of the system by interactions between particles or may be determined by the properties of the continuous phase. The modeling of these processes on a macroscopic level thus presupposes the understanding and quantification on a microscopic level.

Numerical simulations can make a significant contribution to the clarification of these mechanisms when these processes are modeled on particulate scale and basic physical assumptions. However, this requires that suitable numerical methods are used to the movement and interactions of a representative number of particles with sufficient accuracy to map. This requirement is satisfied by the lattice-Boltzmann method [1], based on an efficient discretization of the phase space of the Boltzmann equation. The resulting equations are linear and first order and can be solved with a simple algorithm. Together with the efficient formulation of boundary conditions can be simulated currents through very complex areas of static or moving solids. Modeling the movement and the interactions between particles is based on the Newtonian equations of motion.

The project suspensions of microscale particles under the influence of external fields or shear forces are investigated. The basis for the modeling is the process of Ladd [2,3].