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Graduation February 28, 2012 08:13

Transient simulation diverges

I have some problems with my transient simulation. I use a nearly converged steady state solution (convergence is not possible due to transient flow phenomena) and have tried various time steps. My transient simulation starts normal and every coefficient loop takes 2-4 iterations. However at some point it cannot reach convegence in 4 iterations loops and immediatly the coefficient loop iterations starts to bounce.

So first I have good convergence (2-4 iterations per coefficient loop) and then it goes from good to divergence in one step. So no coefficient loops of 5-9 iterations can be seen in the simulation.

I tried different time steps also adaptive time steps but there is no difference. Is there some-one who has experienced with such behaviour and knows how to deal with it?

Thank you!

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