SimScale CAE Forum

What happens in a CFD simulation if some faces have no boundary condition assigned to them?

Often we receive a warning when performing CFD simulations:
‘Warning: Some faces are missing a boundary condition assignment. If you choose to proceed, a no-slip wall boundary will be assumed for those faces.’

The following information will help:

1.There seems to be a physical variable which is not constrained by a boundary condition.
2.In CFD analysis, every physical variable has to be constrained by at least one boundary condition to have a well-posed problem.
3.If a boundary condition is not assigned by the user, a no-slip wall boundary will be assumed.
4.Please update your boundary conditions such that every face of your geometry has a prescribed boundary condition for every variable visible in the “Boundary Conditions” section of the simulation.

  1. Please note this is just a warning and the simulation can be executed even if this warning pops out.

However, the results are not guaranteed as the platform assumes ‘No-slip wall’ as default and is naive to the physical behavior that user wants to simulate.

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