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Convergence Problems

Question asked by Dario Denzler on Mar 29, 2019
Latest reply on Apr 2, 2019 by Peter Francis

Hello everyone,

 

I am facing some convergence issues in a flow simulation. Basically, I do have a housing with air with the following boundaries:

 

Inlet: 2 faces with ambient pressure

Outlet: 3 faces with ambient pressure

Fans: Internal fan simplified with fan curve

 

Inside the housing, there are some channels which should guide the airflow accordingly. I created goals for volume/mass flow rate for all inlet/outlet. Additionally, I checked the net volume/mass flow (sum of all flows), which should be zero in case of incompressibility from my understanding of fluid dynamics. Well, this is not the case here as I have air, but as pressure differences in this simulation are quite small, I assume this can be neglected.

 

Attached you find plots during the solve for the mentioned goals. After arround 50 iterations, I run into oscillation on the flow rate's @ the inlet's. Now the question is, how to overcome this phenomena. Is the problem not well defined? Too coarse mesh? Maybe some issue with the internal fan (fan curve not suitable)?

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