Defining Boundary and Interface Conditions

To allow the current to enter and leave the domain, set the electric potential or specific electric current at the “inlets” and “outlets” to the electrified domain, for example at the terminals. The current density is considered to be solenoidal, which is equivalent to an incompressibility condition for fluids. Therefore, the amount of current going into the domain is the same as the current leaving it.

When defining the boundary conditions, different techniques are available. For example, consider a wire for which the resistance R and the current I are known. In this case, there are three possible ways to set the boundary conditions:

  • Knowing I and the inlet area, you can determine J. You then apply it with a positive sign at the inlet, and define a constant electric potential at the outlet. (Recommended).
  • Based on I and R, you can deduce the potential difference. You then specify the electric potential at both ends of the wire to reflect the potential difference.
  • Knowing I and the inlet area, you can determine J. You then apply it with a positive sign at the “inlet” and a negative sign at the “outlet”.

Specify appropriate boundary conditions at each boundary:

  1. Expand the relevant Regions > [Region] > Boundaries > [Boundary] > Physics Conditions node.
  2. Select the Electric Potential Specification node and set Method as appropriate:
    • To prevent electric current from crossing the boundary, select Insulator.
    • To specify the electric potential, the electric current density, the specific electric current density, or the total electric current at the boundary, select the corresponding method.
    • To define a characteristic relation of electric current to electric potential drop at the boundary, select Electric Current Potential Characteristic.
  3. Based on the selected method, specify the relevant quantities under the Boundaries > [Boundary] > Physics Values node.
    For information on the available methods and associated values, see:
As with boundaries, you can also set a specific electric current or total electric current value on an interface. For more information, see:

Additionally, at an interface between a solid region and a fluid region that uses the Porous Media model, you can choose to interface the solid region with either the fluid region or with a solid phase contained within the fluid region. To set the interface:

  1. Expand the relevant Interfaces > [Solid/Fluid Interface] > Physics Conditions node.
  2. Select the Electrodynamic Phase Contact Option node and set Phase to one of the following:
    • To exchange the electric solution between the solid region and the fluid region, set Phase to Physics Continuum. This option requires you to activate the Electrodynamic Potential model in both the physics continuum associated with the solid region and the physics continuum associated with the fluid region.
    • To exchange the electric solution between the solid region and a solid phase within the fluid region, set Phase to the relevant solid phase. This option requires you to activate the Electrodynamic Potential model in both the physics continuum associated with the solid region and the phase models associated with the solid phase.