Selecting the Right Physics Interface

The branch (

) included with the CFD Module has a number of subbranches to describe momentum transport. These can be added either singularly or in combination with other physics interfaces modeling mass and energy transfer, and even chemical reactions.

Different types of flow require different equations to describe them. If the flow type to model is known, then select it directly. However, when you are not certain of the flow type, or when it is difficult to obtain a solution, you can instead start with a simplified model and add complexity as you build the model. Then you can successively advance forward, comparing models and results. For porous media flow, the interface is a good place to start if this is the case.

In other cases, you might know exactly how a fluid behaves and which equations, models, or physics interfaces best describe it, but because the model is so complex it is difficult to reach convergence. Simplifying assumptions can be made to solve the problem, and other physics interfaces can be better at fine-tuning the solution process for the more complex problem. The next section gives you an overview of each of the physics interfaces to help you choose.

Table 8-1: The Porous Media Flow Default settings
Physics Interface Label	Name	Compressibility	Neglect Inertial Term	Pore Size
Darcy's Law	dl	n/a	n/a	Low porosity and low permeability, slow flow
Two-Phase Darcy’s law	tpdl	n/a	n/a	Low porosity and low permeability, slow flow
Brinkman Equations	br	Incompressible flow	Yes - Stokes-Brinkman	High permeability and porosity, faster flow
Free and Porous Media Flow	fp	Incompressible flow	Not selected	High permeability and porosity, fast flow

Figure 8-1 is an example of the window for where you can select either Compressible or Incompressible flow, and either normal or Stokes Brinkman flow.