I am trying to get an LES case to converge, and I am having some difficulty. The case runs fine in FLUENT, but the pressure residual blows up in OpenFOAM. My mesh is great, timestep is really small (Co <0.05), so I believe my BCs are the problem. In FLUENT the outlet is set to outlet-vent. Can someone tell me how to set that in OpenFOAM. I jus want to double check what I've done.
Currently for U I have:
inletValue uniform (0 0 0);
value uniform (0 0 0);
For P I have:
value uniform 0;
It seems indeed your boundary conditions may lead to these divergence problems, similar problems where found here:
Maybe they have found a solution,
I had a look at the forum, and it helped. I had a question...what outlet Boundary condition in OpenFOAM would match an outlet-vent condition in FLUENT. In FLUENT, the outlet-vent condition allows backflow, but both the outflow and backflow have a pressure drop across the vent, proportional to the velocity (either in or out). Like a loss coefficient for a valve.
Maybe pressureInletVelocity or something similar for U?
I don't think there is a standard boundary condition available that is similar. I did experiment a bit with LES, but I am not an expert. Also I have no experience with Fluent, so I guess I am not the best person to give you more advice.
I only have one more suggestion:
The way you prescribe the Fluent boundary condition sounds like a sponge layer with backflow calculated based on pressure difference, maybe it helps to use
inletOutlet with inletVelocity uniform(0 0 0)?
I will give that a try, they both sound similar. Boundary conditions for LES are very difficult, especially if they arent cyclical.
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