[acalado]

Hi guys,

I'm having some trouble with convergence on my simulation.

It is a long tunnel with some energy source in the middle. It is a transient simulation and I am using a UDF for this energy source which ramps up over time.

I am having serious trouble with stability, and tried a multitude of different settings, and the only thing that works is if I lower the energy URF to 0.1 anything above that causes divergence. If I turn off the energy equation there is also no problems in solving.

I understand that such a low URF may lead to a not completely converged solution, however I am not sure of what else I can do to get any type of solution.

I have tried using AMG flexible and F-Cycle, V-Cycle, increasing the number of sweeps etc. but without luck

I appreciate your help and ideas.
Kind regards,
Andre

[acalado]

UPDATE: I turned off Viscous Heating and appeared to solve the problem (now able to run with URF = 0.7) . Should there be any reason why this setting should be left ON?

The flow I am dealing with is low mach number, however there is a fire source introduced. Viscous heating due to high velocities would be negligible in this case.

Thanks again!