The Surface Reactions Interface
The Surface Reactions (sr) interface (), found under the Chemical Species Transport branch () when adding a physics interface, is used to model the chemical reactions of surface and bulk species on a boundary. Surface species can be transported in the tangential direction of the surface by Fick’s law whereas bulk species are assumed to be immobile on the surface.
The physics interface supports simulation of surface reactions on boundaries in 1D, 2D, and 3D as well as for axisymmetric components in 1D and 2D. The dependent variables are the surface concentrations, cs,i (SI unit: mol/m2) and the bulk concentrations, cb,i (SI unit: mol/m2).
When this physics interface is added, these default nodes are also added to the Model BuilderSurface Properties, No Flux, and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click Surface Reactions to select physics features from the context menu.
Settings
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is sr.
Dependent Variables
Add or remove species and also change the names of the dependent variables that represent the species concentrations. Note that the names can be changed but the names of fields and dependent variables must be unique within a model.
Enter the Number of surface species. Use the Add surface concentration () and Remove surface concentration () buttons as needed. The same number of Surface concentrations cs, cs2, cs3...are then listed in the table.
Enter the Number of bulk species. Use the Add bulk concentration () and Remove bulk concentration () buttons as needed. The same number of Bulk concentrations cb, cb2, cb3...are then listed in the table.
Discretization
To display this section, click the Show button () and select Discretization.
Consistent and Inconsistent Stabilization
To display these sections, click the Show button () and select Stabilization.
By default the Compensate for boundary stretching check box is selected for the Surface Properties node. This section is then used to stabilize the tangential mesh velocity term.
When the Compensate for boundary stretching check box is cleared (not selected), and for fixed geometries or moving geometries, the stabilization has no effect.
See Surface Reaction Equations on Deforming Geometries for more information.