Simulating liquid-vapor phase separation under shear with lattice Boltzmann method

TL;DR

This paper uses the lattice Boltzmann method to simulate and analyze liquid-vapor phase separation under shear, focusing on instabilities, droplet growth, and the effects of shear rate on morphology.

Contribution

It introduces a detailed simulation of phase separation under shear using the Shan-Chen lattice Boltzmann model, highlighting the roles of Kelvin-Helmholtz instability and shear rate effects.

Findings

Kelvin-Helmholtz instability affects interface stability.

Droplet elongation increases with shear rate.

Hydrodynamic effects dominate near walls, diffusion in bulk.

Abstract

We study liquid-vapor phase separation under shear via the Shan-Chen lattice Boltzmann model. Besides the rheological characteristics, we analyze the Kelvin-Helmholtz(K-H) instability resulting from the tangential velocity difference of the fluids on two sides of the interface. We discuss also the growth behavior of droplets. The domains being close to the walls are lamellar-ordered, where the hydrodynamic effects dominate. The patterns in the bulk of the system are nearly isotropic, where the domain growth results mainly from the diffusion mechanism. Both the interfacial tension and the K-H instability make the liquid-bands near the walls tend to rupture. When the shear rate increases, the inequivalence of evaporation in the upstream and coagulation in the downstream of the flow as well as the role of surface tension makes the droplets elongate obliquely. Stronger convection makes easier the transferring of material particles so that droplets become larger.