Learning Forum

[canderous]

I'm modelling a section of an electric vehicle lithium ion battery pack with a serpentine liquid cooling loop, for the geometry I imported a solidworks assembly where the cells and the loop are separate parts. The model appears to be able to mesh, until I get error messages regarding overlapping contact regions.

I really don't understand what I'm supposed to do to get around this and fix it, I've tried many things such as using the share topology function in design modeler, converting the assembly into a solidworks part file, making the geometry a single part in design modeler, importing as .step and .igs, etc.

Any help is appreciated, thanks

[Rob]

I'm not sure where all the fluid is, but I suspect the contact regions are Meshing being overly sensitive with the tolerances. Can you confirm the surfaces between the annular volumes have a finite area? If you delete all of the contact regions you should be OK. But, you do need to check you have all the correct volumes in the domain.

[canderous]

Thanks for responding.
The fluid domain is inside the wavy tube in between the cells. I've tried fiddling with the tolerances in the contacts menu to no avail. I've thought about just deleting all the contact regions but would this still make the simulation run properly? Is there anything I have to do to compensate for these missing contact regions? Also sorry but which surfaces/volumes are you actually referring to and how do I know these are correct?

[Rob]

Contact regions are to allow the solvers to pass information between disconnected surfaces as long as they're fairly close together (based on solver tolerances). If you only intend and expect to pass heat where the faces actually touch they're not necessary. However, because parts of those faces are in very close proximity the meshing tool thinks they should be in contact: it's a tolerance rule and whilst useful can be a little overzealous in it's choices.

[canderous]

Thank you so much for explaining this, I think it goes to show that I had a fundamental misunderstanding of what contact regions were used for.

[Rob]

It's from the Mechanical tools: they use contact to describe how solids interact. So a contact might be fixed ie glue or allow two bodies to slide over each other, or separate etc. In Fluent we use an interface where we don't want the mesh to match between zones but do want to pass heat and mass. They're less commonly used in CFD simple because a conformal mesh is generally better.