Numerical simulation of two-phase incompressible viscous flows using general pressure equation

TL;DR

This paper extends the general pressure equation (GPE) method for efficient, explicit simulation of two-phase incompressible viscous flows with variable density and viscosity, avoiding the Poisson pressure solve.

Contribution

It generalizes the GPE for two-phase flows, incorporating variable density, viscosity, and surface tension effects with a phase-field model and customized discretizations.

Findings

Accurate simulation of two-phase flows in various geometries.

Comparable results to established methods like LBM.

Reduced memory usage compared to LBM.

Abstract

The general pressure equation (GPE) is a new method proposed recently by Toutant (J. Comput. Phys., 374:822-842 (2018)) for incompressible flow simulation. It circumvents the Poisson equation for the pressure and performs better than the classical artificial compressibility method. Here it is generalized for two-phase incompressible viscous flows with variable density and viscosity. First, the pressure evolution equation is modified to account for the density variation. Second, customized discretizations are proposed to deal with the viscous stress terms with variable viscosity. Besides, additional terms related to the bulk viscosity are included to stabilize the simulation. The interface evolution and surface tension effects are handled by a phase-field model coupled with the GPE-based flow equations. The pressure and momentum equations are discretized on a stagger grid using the second order centered scheme and marched in time using the third order total variation diminishing Runge-Kutta scheme. Several unsteady two-phase problems in two dimensional, axisymmetric and three dimensional geometries at intermediate density and viscosity ratios were simulated and the results agreed well with those obtained by other incompressible solvers and/or the lattice-Boltzmann method (LBM) simulations. Similar to the LBM, the proposed GPE-based method is fully explicit and easy to be parallelized. Although slower than the LBM, it requires much less memory than the LBM. Thus, it can be a good alternative to simulate two-phase flows with limited memory resource.