The Flow through Porous Media processor will analyze fluid flow through a fully saturated porous medium. The flow must be steady, incompressible and isothermal and must maintain its dimensional integrity. The permeability of the medium can be independent of direction or can vary in orthogonal directions. This processor can calculate the flow in a 2-D planar, 2-D axisymmetric or 3-D configuration. The Flow through Porous Media processor can support multiple parts. Each part can have an individual permeability. A part can also be used to model unrestrained flow as the fluid moves between porous media.
The flow can be generated by pressures and velocities. At least one pressure load must be applied to the model so that a reference is established. Any free surface without a velocity or pressure applied will be considered impermeable; that is, the fluid can flow parallel to the surface but cannot pass through it.
Flow through Porous Media assumes that the effects at the wall are negligible compared to the flow through the porous media. Therefore the walls are analyzed with a slip-condition. That is, the velocity at the wall cannot be set to 0.
For situations where a no-slip wall condition (0 velocity at the wall) is important, the alternative is to analyzed the model in 3-D fluid flow with the "Viscosity Model" of the appropriate parts set to "Porous Media Model". Since fluid flow is more comprehensive in its approach, the runtime will be much longer.
The Flow through Porous Media processor uses Darcy's Law, which states
where u is the velocity vector, m the viscosity of the fluid, K the permeability tensor, and p the pressure. The permeability tensor is defined as
The porous medium is considered to be isotropic if the three K components are equal.