Dual Porosity Medium
Use the Dual Porosity Medium if the flow through macropores is governed by Darcy’s law and the micropores do not significantly contribute to the overall flow in the porous medium.
The feature has three default subfeatures —the Fluid subfeature where the fluid density ρ (SI unit: kg/m3) and dynamic viscosity μ (SI unit: Pa·s) are defined, the Macropores subfeature where the hydraulic properties of the macroporous matrix are defined, and the Micropores where the hydraulic properties of the microporous matrix are defined.
Coordinate System Selection
Select a coordinate system from the Coordinate system list for the interpretation of directions in anisotropic material properties. The default is the Global coordinate system, and the list contains any additional orthonormal coordinate system (except boundary coordinate systems) added under the Definitions node.
The subnodes inherit these coordinate system settings. In particular, the Permeability or Hydraulic conductivity (in the Macropores and Micropores subnodes) should be set according to the coordinate system selected in this section.
Storage Model
Choose from a list one of the following formulations:
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From density and porosity (default), uses the formulation equivalent to Equation 7-1
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Linearized storage, where the following linear equation is used to define the storage in the macropores as Sp = εpχf + (1 − εp)χp and in the micropores as Sp,m = εp,mχf + (1 − εp,m)χp.
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Poroelastic storage, where Sp = εpχf in the macropores and Sp,m = εp,mχf in the micropores.
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Quasistatic, where the storage term is set to zero
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User defined to directly specify the storage coefficient Sp and Sp,m for the macro- and micropores respectively.
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Storage Models in the Subsurface Flow Module User’s Guide
Interporosity Flow
Specify the Fluid Transfer Function αw which is used to calculate the interporosity flow, the mass exchange between macro- and microscale system:
(7-5)
with pM being the pressure within the macropores and pm the pressure within the micropores.
Find more information in the Subsurface Flow Module User’s Guide
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Dual Porosity & Dual Permeability Modeling
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Dual Porosity and Dual Permeability Theory
Note that some options are only available in some modules. For a detailed overview of the functionality available in each product, visit https://www.comsol.com/products/specifications/
Location in User Interface
Context Menus
Darcy’s Law > Dual Porosity/Permeability > Dual Porosity Medium
Richards’ Equation > Dual Porosity/Permeability > Dual Porosity Medium
Ribbon
Physics tab with Darcy’s Law or Richards’ Equation selected:
Domains > Dual Porosity/Permeability > Dual Porosity Medium