Mass Flux, Interface
Use the Mass Flux, Interface node to add a mass flux on the exterior interfaces of a layered shell.
It is often possible to determine the mass flux from the pumping rate or from measurements. With this boundary condition, positive values correspond to flow into the model domain:
where N0 is a value or expression for the specified inward (or outward) Darcy flux.
Interface Selection
Set the interfaces for which the mass flux should be specified. Note that it can only be applied to exterior interfaces of the layered shell.
The available options in the Apply to list are Top interface, Bottom interface, Exterior interfaces (which is the default setting) and Selected interfaces. With the last option you can select a set of interfaces and the layered material for which the boundary condition should be active. Note that the checkboxes for internal interfaces between layers are deactivated for this node.
The top and bottom interfaces refer respectively to the upside and downside of the boundary, defined from the orientation of the normal vector. You can visualize the selected interfaces by clicking the Layer Cross Section Preview () and Layer 3D Preview () buttons.
For a general description of layer and interface selections, see Layer and Interface Selection Tools in the Heat Transfer Module User’s Guide.
Constraint Settings
To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog.
For detailed information about the Constraint settings menu see section Constraint Settings in the COMSOL Multiphysics Reference Manual.
Mass Flux, Interface
Enter a value or expression for the Inward mass flux N0. A positive value of N0 represents an inward mass flux whereas a negative value represents an outward mass flux. The units are based on the geometric entity: Boundaries: (SI unit: kg/(m2·s)).