COMSOL 6.4 - The Multiphase Free and Porous Media Flow Interface

The Multiphase Free and Porous Media Flow Interface

The interface (

) combines the interface with the and interfaces to model the transport of multiple immiscible phases in coupled free and porous media flow.

When a predefined interface is added from the branch (

) of the or window, the and interfaces are added to the Model Builder. In addition, the node is added, which automatically includes the , the , and the multiphysics couplings.

On the Constituent Physics Interfaces

The interface is used to simulate the transport of multiple immiscible species in free and porous media flow and solves for their averaged volume fractions (also called saturations). The interfaces between the different phases are not tracked explicitly, although microscopic interfacial effects are taken into account in the macroscopic equations through the capillary pressure functions in porous domains.

The interface is used to simulate fluid flow through interstices in a porous medium. It can be used to model low-velocity flows in media where the permeability and porosity are very small, and for which the pressure gradient is the major driving force and the flow is mostly influenced by the frictional resistance within the pores.

The interface is used to compute the velocity and pressure for a fluid flow in the laminar flow regime. A flow will remain laminar as long as the Reynolds number is below a certain critical value. At higher Reynolds numbers, disturbances have a tendency to grow and cause transition to turbulence.

Settings for Physics Interfaces and Coupling Features

When physics interfaces are added using the predefined couplings, for example , specific settings are included with the physics interfaces and the coupling features.

However, if physics interfaces are added one at a time, followed by the coupling features, these modified settings are not automatically included.

Table 7-3: Modified Settings for a multiphase free and porous media flow interface.
Physics Interface or Coupling Feature	Modified Settings
Darcy’s Law	In the Darcy’s Law interface, linear shape functions are used for the discretization of the pressure.
Multiphase Flow in Porous Media	The Domain Selection is the same as that of the participating physics interfaces. The corresponding Phase Transport in Free and Porous Media Flow and Darcy’s Law interfaces are preselected in the Coupled Interfaces section.
Mixture Model	The Domain Selection is the same as that of the participating physics interfaces. The corresponding Phase Transport in Free and Porous Media Flow and Laminar Flow interfaces are preselected in the Coupled Interfaces section.
Free and Porous Media Flow Coupling	The Boundary Selection is the same as that of the participating physics interfaces. The corresponding Laminar Flow and Darcy’s Law interfaces are preselected in the Coupled Interfaces section.