.. _InputsPorousMediaDefs:

Porous media
============

Homogeneous porous media are modeled by the addition of a momentum
source term, :math:`\boldsymbol{S}_{pm}`, to the fluid momentum equation.

.. math::

   \boldsymbol{S}_{pm} =-\frac{\mu_f}{C_1} \boldsymbol{u}_f - C_2\frac{1}{2}\rho_f\lvert \boldsymbol{u}_f \rvert \boldsymbol{u}_f

:math:`\mu_f`, :math:`\rho_f`, and :math:`\boldsymbol{u}_f` are the fluid viscosity, density, and velocity and
:math:`C_1` and :math:`C_2` are user defined constants.

The following inputs are defined using the ``pm`` prefix.

+--------------------------+------------------------------------------------------------------------------+----------+-----------+
|                          | Description                                                                  |   Type   | Default   |
+==========================+==============================================================================+==========+===========+
| regions                  | Regions used to define porous media.                                         | String   |  None     |
+--------------------------+------------------------------------------------------------------------------+----------+-----------+
| [region].volfrac         | Solids volume fraction of the porous media region.                           |  Real    |  None     |
+--------------------------+------------------------------------------------------------------------------+----------+-----------+
| [region].c1              | Porous media permeabilty constant for the source term in fluid               |  Real    |  None     |
|                          | momentum equation.                                                           |          |           |
+--------------------------+------------------------------------------------------------------------------+----------+-----------+
| [region].c2              | Porous media inertial resistance factor for the source term in fluid         |  Real    |  None     |
|                          | momentum equation.                                                           |          |           |
+--------------------------+------------------------------------------------------------------------------+----------+-----------+
| [region].allow_particles | Allow particles to flow through the porous media region.                     |  Int     |    0      |
+--------------------------+------------------------------------------------------------------------------+----------+-----------+