Application of Implicit treatment of coupled boundary conditions to heat exchange
Summary
The problem is related to the newly developed implicit treatment of mapped boundary condition (for next release 2112). In particular, the issue appears when the implicit treatment is applied to solve the temperature field at the interface of fluid and solid regions with the chtMultiRegionSimpleFoam solver.
Steps to reproduce
Use the chtMultiRegionSimpleFoam solver to run, on a single processor, the attached case with the flag "useImplicit" set to true or false for interface patches named "fluid_higher_to_solid" and "fluid_lower_to_solid" for the fluid and the corresponding patches "solid_to_fluid_higher" and "solid_to_fluid_lower" in the solid region to reproduce the explicit and implicit solutions.
Example case
Attached (test_parallelPlates.tar) you can find a rectangular case with two fluid regions and a solid region in between. They schematized two consecutive channels of a counter-flow compact heat exchanger. In the upper fluid region named "fluid_higher" the cold flow is heated by the hot flow flowing in the lower fluid region named "fluid_lower". The solid region named "solid" represents the heat exchanger. This test case was originally developed to check some user code implementation but, in the reported tests, only standard libraries are employed.
What is the current bug behaviour?
The results of the temperature field with the explicit treatment are correct, while the same setup with the implicit treatment gives nonphysical values.
What is the expected correct behavior?
For a steady state case, after enough iterations, the results of implicit and explicit treatments setups should be the same.
Relevant logs and/or images
Scheme of the testes configuration.
Comparison of the mas averaged outlet temperature of the heated cold flow with different setups/solver of different version:
Computed Temperature fields:
| Explicit treatment | Implicit treatment |
|---|---|
 |
 |
Environment information
- OpenFOAM version : development (next release 2112)
- Operating system : Mint 19.1 Cinammon
- Hardware info :
- Compiler :