Modeling Ohmic Heating

Simcenter STAR-CCM+ allows you to calculate the heat that is generated by electric currents flowing in resistive materials. You can use the Ohmic Heating model in combination with an energy model.

The ohmic heat source is proportional to the electric current density and the electric field (see Eqn. (4357)). To account for Ohmic heating:

Prepare the electromagnetic analysis following the guidelines outlined in the previous sections, Modeling Electric Currents and Modeling Magnetic Fields. In the physics continua associated with electrically conducting regions, activate the required potential models.
Complete the electromagnetic analysis set up, by specifying appropriate boundary, interface, and region settings. For guidelines, see Modeling Electric Currents and Modeling Magnetic Fields.
If you define an electric resistance at a boundary or interface, Simcenter STAR-CCM+ also accounts for the energy dissipation due to the specified resistance (see Eqn. (4360)).
Optionally, you can activate an energy model and specify settings for thermal analysis. All energy models, including the Finite Element Solid Energy model for solids, are compatible with the Ohmic Heating model.
When the continuum contains an energy model, Simcenter STAR-CCM+ accounts for the heat source calculated by the Ohmic Heating model in the energy equation. In thermal analyses of electrically conducting materials, you generally account for Ohmic heating when the Ohmic heat source is significant compared to all other source terms in the energy equation. For more information, see Joule Heating.
Activate the Ohmic Heating model in the physics continua that are assigned to the electrically conducting regions.
For more information on the model dependencies and associated field functions, see Ohmic Heating Model Reference.
To model Ohmic heating in porous media, follow the additional steps in Modeling Ohmic Heating in Porous Media.
In all physics continua that use the Ohmic Heating model, expand the relevant [Physics Continuum] > Models > [Material Model] > Material Properties node.

Select the Electrical Conductivity node and specify the electrical conductivity of the material using an appropriate method.

In thermal analyses, the electrical conductivity of a material is generally a function of temperature and, therefore, it has a high impact on the accuracy of the heat calculation. When the temperature change is relatively small, you can neglect the dependency of the material electrical conductivity on temperature. When the temperature change is significant, define the electrical conductivity as a function of temperature using one of the following methods:

Option	Steps
To define $σ$ as a polynomial function of temperature	Select Polynomial in T. Define the polynomial function using the Electrical Conductivity > Polynomial in T node. See Using Polynomial in T.
To define $σ$ using a table of $σ, T$ values	Select Table (T). Define the input table using the Electrical Conductivity > Table (T) node. See Using Table(T).
To define $σ$ using a user-defined function of temperature	Select Field Function. Under the Automation > Field Functions node, create an appropriate temperature-dependent field function (see Creating a User Field Function). Finally, select the Electrical Conductivity > Field Function node and set Scalar Function to the user field function that you created.
To define an anisotropic $σ$	Select Anisotropic. In the relevant regions, select the Anisotropic Electrical Conductivity node and define the components of the second-order tensor $σ$ as a function of temperature. See Tensor Quantities.

Prepare the required scenes and plots for post-processing and run the simulation.

The specific Ohmic heat source (Eqn. (4357)) can be significantly large at the beginning of the solution process, causing the energy solution to diverge.

If the energy solution is diverging during initial iterations, you can:
- Examine the critical areas where the ohmic heat source term is large, using the Specific Ohmic Heat Source field function. Evaluate whether the mesh quality can be improved in these areas.
- In the relevant physics continuum Reference Values, reduce the maximum allowable temperature. This option is not available for the Finite Element Solid Energy model.
- In thermal analyses, decouple the thermal and the electromagnetic solutions. That is, freeze the energy solver and get a converged solution for the potentials then activate the energy solver to continue with the thermal analysis.