### 12.4.7. Porosity Settings Tab

The Porosity Settings tab is where the general description of a porous domain is specified for the simulation.

#### 12.4.7.1. Area Porosity

Area Porosity represents the fraction of physical area that is available for the flow to go through. The default setting is `Isotropic`.

#### 12.4.7.2. Volume Porosity

Volume Porosity is the local ratio of the volume of fluid to the total physical volume.

#### 12.4.7.3. Loss Models

The porous loss options are:

- Isotropic Loss

  For the isotropic loss model, the loss may be specified using either one of the following methods:

  - Permeability And Loss Coefficient

  - Linear And Quadratic Resistance Coefficients

- Directional Loss

  Specify the streamwise direction via Cartesian or cylindrical components (in the coordinate frame specified on the Basic Settings tab).

  The loss in the streamwise direction can be specified using one of the following options:

  - Permeability And Loss Coefficient

  - Linear And Quadratic Resistance Coefficients

  - No Loss

  The loss in the transverse directions can be specified using one of the following options:

  - Streamwise Coefficient Multiplier

  - Permeability and Loss Coefficient

  - Linear and Quadratic Resistance Coefficients

  - No Loss

- None

When specifying the loss coefficients, it is important to set the Loss Velocity Type properly. For details, see Porous Momentum Loss Models in the CFX-Solver Theory Guide.

#### 12.4.7.4. Contact Area Model

This setting is available only when the porous domain has a solid phase.

When there is more than one fluid in a porous domain that has a solid phase, specify the contact area model to indicate how the contact area between a given fluid and the solid is to be calculated.

The options are:

- Use Volume Fraction

  This option makes use of the volume fraction of each fluid to calculate the contact area between that fluid and the solid.

- Fluid Dependent

  This option enables the direct specification of the contact area fraction for each fluid. The area fractions must sum to unity.

#### 12.4.7.5. Fluid Solid Area Density

This setting is available only when the porous domain has a solid phase.

Specify the fluid-solid area density, which is the contact area per unit volume, where the contact area is the surface area of the solid in contact with the fluid(s).

#### 12.4.7.6. Fluid Solid Heat Transfer

This setting is available only when the porous domain has a solid phase.

Specify the overall heat transfer coefficient for heat transfer between the fluid(s) and the solid. This is analogous to the heat transfer coefficient between fluids in an inhomogeneous multiphase case, as described in Inhomogeneous Interphase Heat Transfer Models.

#### 12.4.7.7. Additional Variable Pair Details

This setting is available only when the porous domain has a solid phase.

Specify pairs of the same Additional Variable to enable the Additional Variable transfer between the solid and the fluid(s).

The options are:

- Additional Variable Transfer Coefficient

  This option applies a bulk value of the Additional Variable transfer coefficient between the fluid(s) and the solid.

- Fluid Dependent

  This option enables the direct specification of the Additional Variable transfer coefficient for each fluid.

The Additional Variable transfer coefficient is analogous to the transfer coefficient between fluids in an inhomogeneous multiphase case. For details, see Additional Variable Interphase Transfer Models in the CFX-Solver Modeling Guide and Additional Variables in Multiphase Flow in the CFX-Solver Theory Guide.

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