Discrete exterior calculus discretization of two-phase incompressible Navier-Stokes equations with a conservative phase field method

TL;DR

This paper introduces a novel discretization scheme based on discrete exterior calculus for simulating two-phase incompressible flows, ensuring physical compatibility, boundedness, and mass conservation even with large property contrasts.

Contribution

The paper extends DEC discretization to two-phase flows with discontinuous properties, providing a bounded, conservative, and coordinate-independent numerical scheme.

Findings

The scheme remains bounded without ad hoc mass redistribution.

It accurately captures interfaces on flat and curved domains.

It handles large density and viscosity ratios effectively.

Abstract

We present a discrete exterior calculus (DEC) based discretization scheme for incompressible two-phase flows. Our physically-compatible exterior calculus discretization of single phase flow is extended to simulate immiscible two-phase flows with discontinuous changes in fluid properties such as density and viscosity across the interface. The two-phase incompressible Navier-Stokes equations and conservative phase field equation for interface capturing are first transformed into the exterior calculus framework. The discrete counter part of these smooth equations is obtained by substituting with discrete differential forms and discrete exterior operators. We prove the boundedness of the method for the first order Euler forward and predictor-corrector time integration schemes in the DEC framework. With a proper choice of two free parameters, the scheme remains phase field bounded without the requirement of any ad hoc mass redistribution. We verify the scheme against several standard test cases (for interface capturing) comprising not only the flat domains but also the curved domains, leveraging the advantage that DEC operators are independent of the coordinate system. The results show excellent properties of boundedness, mass conservation and convergence. Moreover, we demonstrate the ability of the scheme towards handling large density and viscosity ratios as well as surface tension in the simulation of various two phase flow physical phenomena on flat or curved surfaces.