Lattice Boltzmann simulation of vortices merging in a two-phase mixing layer

Abstract

Mixing layers are commonly observed in flow fields of many types of industrial equipment such as combustion chambers, chemical reactors, and fluid ejectors. It is important to effectively mix two co-flowing gaseous/fluids streams in such equipment. As the mixing of two fluids is an interface and surface tension dominated process, numerical simulations of the mixing process are generally very complex. The present study is concerned with using the lattice Boltzmann method (LBM) to study vertices merging in a two-dimensional two-phase spatial growing mixing layer. Different velocity perturbations are forced at the entrance of the flow field of a rectangular mixing layer; the initial interface between twophases is evenly distributed around the midpoint in a vertical direction. By changing the strength of surface tension and combinations of perturbation waves, the effects of surface tension and velocity perturbation on vortices merging are investigated. Some interesting phenomena, which have not occurred in a singlephase mixing layer, are observed and the corresponding mechanism is discussed.