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Modelling using darcy law for multiphase flow in porous media

Posted Feb 20, 2019, 7:18 a.m. EST Fluid & Heat, General, Heat Transfer Version 5.4 1 Reply

Swati Gupta
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I am trying to model a system having 2 phases. I am using physics Multiphase Transport in porous media, which by default adds two physics - Phase Transport in Porous Media and Darcy Law interface coupled by multiphysics. I want to solve pressure for both two phases, water and gas which gives velocities for both water and gas. But this interface only solves for one pressurre and only one velocity. But in Phase Transport in Porous Media solves for 2 saturation, one gas and one water. How can I do so?

1 Reply Last Post Mar 7, 2019, 4:17 a.m. EST
Tycho van Noorden COMSOL Employee

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Posted: 5 years ago Mar 7, 2019, 4:17 a.m. EST

Dear Swati Gupta,

If you use the Multiphase Flow in Porous Media multiphysics interface, which couples a Darcy's Law interface and a Phase Transport in Porous Media interface, the Darcy's Law interface indeed computes for the pressure of only one phase. However, from this pressure of one phase, the Phase Transport in Porous Media interface computes the pressures of both phases, using a capillary pressure function. From these two pressures, the velocities for both phases are then computed. These pressures are usually called phtr.p_s1 and phtr.p_s2, and the velocities are usually called (phtr.ux_s1,phtr.uy_s1,phtr.uz_s1) and (phtr.ux_s2,phtr.uy_s2,phtr.uz_s2). These variables can be used for plotting and are available in the plot menu. More details can be found in the Subsurface Flow Module User's Guide.

Another approach for two-phase flow in a porous medium, can be found in the following example model: https://www.comsol.nl/model/two-phase-flow-experiment-499 where two Darcy's Law interface are used.

In principle the two approaches (two Darcy's Law interfaces or the Multiphase Flow in Porous Media multiphysics interface) should give the same results.

Best regards, Tycho van Noorden, COMSOL

Dear Swati Gupta, If you use the Multiphase Flow in Porous Media multiphysics interface, which couples a Darcy's Law interface and a Phase Transport in Porous Media interface, the Darcy's Law interface indeed computes for the pressure of only one phase. However, from this pressure of one phase, the Phase Transport in Porous Media interface computes the pressures of both phases, using a capillary pressure function. From these two pressures, the velocities for both phases are then computed. These pressures are usually called phtr.p_s1 and phtr.p_s2, and the velocities are usually called (phtr.ux_s1,phtr.uy_s1,phtr.uz_s1) and (phtr.ux_s2,phtr.uy_s2,phtr.uz_s2). These variables can be used for plotting and are available in the plot menu. More details can be found in the *Subsurface Flow Module User's Guide*. Another approach for two-phase flow in a porous medium, can be found in the following example model: [https://www.comsol.nl/model/two-phase-flow-experiment-499](https://www.comsol.nl/model/two-phase-flow-experiment-499) where two Darcy's Law interface are used. In principle the two approaches (two Darcy's Law interfaces or the Multiphase Flow in Porous Media multiphysics interface) should give the same results. Best regards, Tycho van Noorden, COMSOL

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