The Flux/Source boundary condition adds a flux or source
g on the boundary:
The first equation describes this boundary condition for a Coefficient Form PDE, and the second term describes it for a General Form PDE. The g term may contain a general expression of the dependent variables. The
q coefficient simplifies the implementation of a
Robin boundary condition by including a term on the form
qu, where
u is the dependent variable.
By default, all checkboxes are selected for the Diffusive flux,
Conservative convective flux, and
Nonconservative convective flux to include all flux components. You can use the Flux/Source boundary condition in the Stabilized Convection-Diffusion Equation interface as an outflow condition by clearing the
Nonconservative convective flux and
Conservative convective flux checkboxes and as a supersonic outflow condition by clearing all checkboxes so that the flux is computed from inside the domain.
Enter a value or expression for the value of the coefficient q in the corresponding field or fields. The default value is 0. It adds a term
qu to the boundary flux or source, which can represent absorption or impedance at the boundary.
For the Stabilized Convection-Diffusion Equation, there is an additional flux term, (k ·
n)
u, so, in addition, you can enter the components of the
k vector in the corresponding text fields.
or 