Control of droplet collapse during coarsening process by imposing shear flow: a lattice Boltzmann simulation

Abstract

The effects of shear flow on droplet collapse during the coarsening process in a vapor–liquid system are investigated by a free energy lattice Boltzmann model. To simulate different viscosity ratios, a local relaxation time parameter is integrated with LBM algorithm. The results show that for zero and small shear rates, droplet coarsening happens in its regular pattern where small droplet is collapsed while greater one grows (sub-critical regime). But if the shear rate be greater than a critical value, collapse is abated, droplet coarsening is inverted and smaller droplet grows (super-critical regime). Therefore during coarsening process, collapse mechanism can be controlled by imposing suitable shear flow. Also it is shown that, higher droplet radius ratio, viscosity ratio and surface tension lead to higher critical shear rate of collapse while higher density ratio of liquid and vapor decreases that.