This condition node adds a boundary condition for the species concentration. For example, a c = c0 condition specifies the concentration of species c.

Individually specify the concentration for each species. Select the check box for the Species to specify the concentration, and then enter a value or expression in the corresponding field. To use another boundary condition for a specific species, click to clear the check box for the concentration of that species.

To display this section, click the Show button () and select Advanced Physics Options. You can find details about the different constraint settings in the section Constraint Reaction Terms in the COMSOL Multiphysics Reference Manual.