Discrete Boltzmann modeling of multiphase flows: hydrodynamic and thermodynamic non-equilibrium effects

TL;DR

This paper develops a discrete Boltzmann model to analyze non-equilibrium effects during phase separation, providing insights into the roles of latent heat and surface tension in multiphase flows.

Contribution

The paper introduces a novel discrete Boltzmann model that quantifies hydrodynamic and thermodynamic non-equilibrium effects in phase separation processes.

Findings

TNE strength peaks at the end of spinodal decomposition

Latent heat reduces maximum TNE intensity

Surface tension prolongs spinodal stage and accelerates domain growth

Abstract

A discrete Boltzmann model (DBM) is developed to investigate the hydrodynamic and thermodynamic non-equilibrium (TNE) effects in phase separation processes. The interparticle force drives changes and the gradient force, induced by gradients of macroscopic quantities, opposes them. In this paper, we investigate the interplay between them by providing detailed inspection of various non-equilibrium observables. Based on the TNE features, we define a TNE strength which roughly estimates the deviation amplitude from the thermodynamic equilibrium. The time evolution of the TNE intensity provides a convenient and efficient physical criterion to discriminate the stages of the spinodal decomposition and domain growth. Via the DBM simulation and this criterion, we quantitatively study the effects of latent heat and surface tension on phase separation. It is found that, the TNE strength attains its maximum at the end of the spinodal decomposition stage, and it decreases when the latent heat increases from zero. The surface tension effects are threefold, to prolong the duration of the spinodal decomposition stage, decrease the maximum TNE intensity, and accelerate the speed of the domain growth stage.