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pakanatiakash June 12, 2014 07:36

Divergence error

I am new to AVL Fire and I am trying to simulate melting phenomena using the porosity technique available. The case I am taking up is a simple Stefan problem of one dimension. Once I start the iteration I am getting this error, say after 6 iterations -

Problem diverges : Continuity equation, variable: Pressure correction

I tried to change the under relaxation factors and also employed stable schemes but its of no use. The pressure correction is also on.

Could somebody give insight into whats causing this problem. I am using 2011.1 version. Thank you


chang.gaikwad June 13, 2014 02:29

I don't have the experience with the type of problem you are solving. But you might check if you have right pressure initialization. Use the average pressure value that you expect in the CFD domain for initialization. Using zero value of velocity and density sometimes help to give stable start to the problem.

pakanatiakash June 18, 2014 06:01

Thanks for the suggestion. I found the solution but its kind of weird. I ran the simulation in 2013.1 version and it had this problem. I later ran it in 2013.2 version with the same setup and it works just fine. I am assuming there was some bug which was fixed in the later versions. Maybe more specifically in the melting simulation module. But I would like to know if the reason is different from what i thought.

chang.gaikwad June 18, 2014 06:06

I have more weird experience with v2010.1. Sometimes when simulation (transient) diverge just restarting it with last saved BC files will converge it.

Its good to know v2013.2 is doing better job that v2013.1. I am planning to start using v2013.2 soon. Thanks for the feedback.

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