Domain and Boundary Nodes for the Nernst-Planck Equations Interface
The Nernst-Planck Equations Interface has these domain and boundary physics nodes available.
Domain Nodes
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Convection, Diffusion, and Migration
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Reactions
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Equilibrium Reaction is described for the Transport of Diluted Species interface
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Initial Values
Boundary Conditions
In the Nernst-Planck Equations interface, there are separate boundary conditions for the species concentrations and for the electric potential. This means that there are two active boundary conditions on each boundary. Many different combinations of boundary conditions can be set for the electric field and concentration fields on a boundary, but not all combinations are relevant.
Species Concentration Boundary Conditions
The following boundary conditions for the species concentrations are available on exterior boundaries:
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Concentration
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Flux
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No Flux (the default boundary condition for species concentrations)
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Symmetry
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Inflow
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Outflow
For interior boundaries, continuity in the concentration of all species is the default boundary condition. In addition, the Flux Discontinuity boundary condition is available on interior boundaries.
Electric Potential Boundary Conditions
The following boundary conditions for the electric potential are available on exterior boundaries:
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Current Density
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Electric Insulation (the default boundary condition for the electric potential)
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Electric Potential (described for the Electrostatics interface in the COMSOL Multiphysics Reference Manual)
For interior boundaries, continuity in the electric potential is the default boundary condition. In addition, the following boundary conditions are available on interior boundaries:
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Current Discontinuity
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Electric Potential (described for the Electrostatics interface in the COMSOL Multiphysics Reference Manual)
Edges and Points
The Point Mass Source and Line Mass Source features are also available and described for the Transport of Diluted Species interface.
The links to the physics nodes described in the COMSOL Multiphysics Reference Manual do not work in the PDF, only from the online help.
For axisymmetric models, COMSOL Multiphysics takes the axial symmetry boundaries (at r = 0) into account and automatically adds an Axial Symmetry node to the model that is valid on the axial symmetry boundaries only.