Time-step chosen by BDF method?

Topics: Solving

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Guillermo Vilaplana

Guillermo Vilaplana

April 28, 2011 2:07pm UTC

Time-step chosen by BDF method?

Hi,

The time-dependent solver chooses an extremely small time-step, and I can't find how this time-step is chosen.

Any guess?

All what I found is :
"IDA [...] uses variable-order variable-step-size backward differentiation formulas (BDF)."
p 365 Reference Guide


Thank you very much for your help.
Guillermo Vilaplana

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Gabriel Caron

Gabriel Caron

April 28, 2011 7:16pm UTC in response to Guillermo Vilaplana

Re: Time-step chosen by BDF method?

If you want to controle it instead:

Under Study ->SolverConfiguration -> Solver x -> Time-Dependent solver x

Time Stepping Tab.

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Ivar Kjelberg

Ivar Kjelberg

April 28, 2011 8:25pm UTC in response to Gabriel Caron

Re: Time-step chosen by BDF method?

Hi

The time stepper often starts with small steps, as often we are lazy and leave "0" as initial conditions, but true current, or heat flux starting far away from "0" so the system believes its facing a large derivative at the beginning of the transient solver sequence, hence small steps. use better initial conditions with smooth transitions and your solver will converge quicker

--
Good luck
Ivar

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