Conjugate Heat Transfer Coupling of NekRS and MOOSE

These tutorials describe how to couple NekRS to MOOSE through boundary heat transfer by exchanging boundary conditions. Cardinal provides three options for these boundary conditions: - Wall temperature - Wall conductive heat flux (i.e. ) - Wall convective heat flux (i.e.

This type of simulation is referred to as CHT. To set up a well-defined CHT case, you must choose one of these boundary conditions for NekRS to send to MOOSE, and a different boundary condition for MOOSE to send to NekRS. For example, you can build a CHT case which passes temperature from NekRS to MOOSE and the wall conductive flux from MOOSE to NekRS. This is shown below as the "Cond. Flux - Temperature" option.

Figure 1: Illustration of CHT coupling with the "Cond. Flux - Temperature" option

You could also build a CHT case which passes wall conductive heat flux from NekRS to MOOSE and the wall temperature from MOOSE to NekRS. This is shown below as the Temperature - Cond. Flux option.

Figure 2: Illustration of CHT coupling with the "Temperature - Cond. Flux" option

Another CHT option passes the wall convective heat flux from NekRS to MOOSE and the wall conductive flux from MOOSE to NekRS. This is shown below as the Cond. Flux - Conv. Flux option. Note that in all of these options, our naming convention is to list the transfer to NekRS first, and the transfer from NekRS second.

Figure 3: Illustration of CHT coupling with the "Cond. Flux - Conv. Flux" option

schooltip

You might choose to use different boundary conditions in order to improve the stability of the coupling; when Cardinal was first developed, only one option existed - the "Cond. Flux - Temperature" option, even though it is known that this option can be less stable than the others.

Cardinal uses a general formulation that allows NekRS to couple via conjugate heat transfer to any MOOSE thermal-fluid application. This is shown schematically in Figure 4. All tutorials in this section couple NekRS to the MOOSE heat transfer module, but the concepts extend equally to coupling NekRS to any of these other MOOSE thermal-fluid codes.

Figure 4: NekRS integrates with any MOOSE application that can compute a heat flux

Five examples are provided; the "Pin Bundle Flow" example illustrates how to use the above listed examples for CHT boundary conditions for easy comparison. For simplicity, all other examples use the "Cond. Flux - Temperature" option.