Fluid (Porous Medium)
Use this node to specify the properties of the different phases, including their relative permeabilities and capillary pressures.
Model Input
Enter the absolute pressure field (SI unit: Pa) for the phase that is computed from the volume constraint. The volumetric flux of this phase is computed using Darcy’s law, and in many cases that pressure field will be computed for in a Darcy’s Law interface, coupled to the Phase Transport interface using a Multiphase Flow in Porous Media multiphysics coupling node.
The volumetric fluxes of the other phases are also computed using Darcy’s law, taking into account the relative permeabilities and capillary pressures.
Capillary pressure
Select a Capillary pressure model — User defined (the default), van Genuchten, Brooks and Corey, or Capillary diffusion. The van Genuchten and Brooks and Corey options are only available when there are not more than two phases present in the model.
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For User defined, enter an expression for the Capillary pressure pc (SI unit: Pa) for the phases that are not computed from the volume constraint. The pressure of the corresponding phase is equal to the pressure of the phase computed from the volume constraint (supplied in the Pressure input field) plus the capillary pressure supplied for this phase.
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For van Genuchten, select the Wetting phase and enter an Entry capillary pressure pec (SI unit: Pa), the Constitutive relations constant mvG (dimensionless), and Constitutive relations constant lvG (dimensionless).
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For Brooks and Corey, select the Wetting phase and enter an Entry capillary pressure pec (SI unit: Pa) and the Pore size distribution index λp (dimensionless).
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For Capillary diffusion, enter a capillary diffusion coefficient Dc (SI unit: m2/s) for the phases that are not computed from the volume constraint.
Phase properties
Select the material to use for each phase. Select Domain material (the default) from the Fluid list to use the material defined for the domain. Select another material to use that material’s properties.
Enter the Density ρ (SI unit: kg/m3), Dynamic viscosity μ (SI unit: Pa·s) and Relative permeability κr (a dimensionless number between 0 and 1) for each phase. The defaults for the Density and Dynamic viscosity are From material, and User defined for the Relative permeability. For User defined, the default values are 1000 kg/m3, 0.001 Pa·s. and si2, respectively.
The Relative permeability input fields are only available when the Capillary pressure model is set to User defined or Capillary diffusion. In these cases, select either User defined or Power law. When Power law is selected, enter the Exponent qi (dimensionless, default value 2) and the Residual saturation sri (dimensionless, default value 0)
In the other cases (van Genuchten or Brooks and Corey) the relative permeabilities are defined by the van Genuchten or Brooks and Corey model. For the van Genuchten and Brooks and Corey model, specify the Residual saturation sri (dimensionless, default value 0) for each phase.