Micropores
This node defines the porosity and material properties of the microporous matrix of the Dual Porosity Medium, Dual Permeability Medium, or the Unsaturated Dual Permeability Medium parent node.
Model Input
This section is only available for the Unsaturated Dual Permeability Medium parent node and contains fields and values that are inputs for expressions defining material properties. If such user-defined property groups are added, the model inputs appear here.
Matrix Properties
The default Porosity εp,m of the solid matrix of the micropore system is taken From material. Select User defined to enter a value or expression for εp,m.
If required by a Storage model in the parent node, specify the Effective compressibility of the microscale porous matrix. The default value is χp,m = 10−4 1/Pa.
Select a Permeability model to specify the capacity to transmit flow for the porous material of the microscale system. Here, only the Darcian Flow models are available. Select between the following options for the Permeability model:
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Select Permeability (default) to define the permeability of the porous matrix. The default Permeability κm (SI unit: m2) uses the value From material, as defined by the Porous material. For User defined select Isotropic to define a scalar value or Diagonal or Symmetric to define a tensor value.
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Select Hydraulic conductivity or define a combination of fluid permeability and dynamic viscosity. For Hydraulic conductivity Km (SI unit: m/s) select Isotropic to define a scalar value or Diagonal or Symmetric to define a tensor value. The default is 2.94·10−4 m/s.
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Select Kozeny-Carman to define the permeability from the porosity and mean particle diameter. Enter the mean Particle diameter dp,m (SI unit: m), the default value is 0.5 mm.
Retention Model
For an Unsaturated Dual Permeability Medium select between the following options for the retention model:
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From macropores to take over the retention model settings from the Macropores node.
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van Genuchten, to specify the retention model using the van Genuchten relationship. Enter the constitutive relation constants α (the default value is 1, and the SI unit is 1/m), n (default value is 2), and l (default value is 0.5). The constitutive parameter m is equal to 1 − 1 / n.
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Brooks and Corey to use the retention model according to the Brooks and Corey relationships.
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User defined to use a different retention model. Enter user defined expressions for the Effective saturation Se,m, the Liquid volume fraction θl,m. The default is εp,m (the porosity variable). Specify the Specific moisture capacity Cm,m (SI unit: 1/m). The default value is 0 (1/m). Enter an expression for the Relative permeability κr,m. The default value is 1.
If there is a residual volume of liquid that cannot move through the pore network, also enter a value between 0 and 1 for the Residual liquid volume fraction θr. The default value is 0.
Retention and Permeability Relationships in the Subsurface Flow Module User’s Guide
Initial Values
Define the initial pressure of the microscale system. The default is to use the initial values defined in the Initial Values feature node which means that the same initial values apply to the macroscale and the microscale system.
Select User Defined to specify an initial pressure for the microscale system pm0,init.
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/