Convective Term Formulation
The Transport of Diluted Species in Porous Media interface includes two formulations of the convective term. The conservative formulation of the species equations in Equation 4-16 is written as:
(4-20)
If the conservative formulation is expanded using the chain rule, then one of the terms from the convection part, ci∇·u, would equal zero for an incompressible fluid and would result in the non-conservative formulation described in Equation 4-16.
When using the non-conservative formulation, which is the default, the fluid is assumed incompressible and divergence free: ∇ ⋅ u = 0. The non-conservative formulation improves the stability of systems coupled to a momentum equation (fluid flow equation).
To switch between the two formulations, click the Show button () and select Advanced Physics Options. In the section Advanced Settings select either Non-conservative form (the default) or Conservative form. The conservative formulation should be used for compressible flow.