Flow and mixing dynamics of phase-transforming multicomponent fluids

Abstract

Despite the importance of phase-transforming, multicomponent fluids in medical diagnostics, atmospheric flows, or supercavitating vehicles, our understanding of their flow and mixing dynamics is very limited. Here, we investigate two-component flows, where one of the components is an incondensable gas and the other one is a fluid that undergoes liquid-vapor phase transformations accompanied by changes in its miscibility with the gas. We derived a continuum model from a Gibbs free energy that includes gradients of the fluid density and gas concentration, leading to a generalization of the classical equations of multiphase flow hydrodynamics. High-fidelity numerical simulations of the model show a very complex interplay between flow, mixing, and phase transformations. The model predicts quantitatively the saturation vapor pressure of water for a given mixture of air and water vapor at different temperatures. When applied to the problem of collapse of cavitation bubbles, the model allows us to study the role of gas dissolved in the liquid phase in the dynamics of the collapsing bubble. Our findings on the collapse of multicomponent bubbles have a strong bearing on the multiple applications of cavitation bubbles. The proposed model opens entirely different ways to study phase-transforming multicomponent fluids.