Mass Fraction
The Mass Fraction node adds boundary conditions for the species mass fractions. For example, the following condition specifies the mass fraction of species i: ωi = ωi,0.
Set the mass fractions of all species except the one computed from the mass constraint. This ensures that the sum of the mass fractions is equal to one (see Species). This node is available for exterior and interior boundaries.
Mass Fraction
Specify the mass fraction for each species individually. Select the check box for the species to specify the mass fraction, and 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 mass fraction of that species.
Mass Transfer to Other Phases
When using the Reacting Flow coupling feature to model coupled momentum and mass transport, boundary conditions that results in a non-negligible mass flux can be consistently handled by accounting for the The Stefan Velocity.
Select Account for Stefan velocity to update the Stefan velocity in accordance with the prescribed mass fractions. Examples of cases that may benefit from this are for example when modeling surface reactions or phase change on an exterior boundary.
Constraint Settings
To display this section, click the Show button () and select Advanced Physics Options.