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More services...CFD time stepping: CFL vs implicit
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2 Replies
Last post: September 7, 2010 11:31am UTC
September 2, 2010 11:48am UTC
CFD time stepping: CFL vs implicit
Hi,
i'm struggling on which time stepping method for transient fluid-thermal-interaction i should use. (Comsol V3.5a)
The default setting for the stepping for the transient solver is the following:
Time steps taken by solver: "Manual"
Time Step: "5*dt_cfl_g1_chns"
So the time stepping is explicit based on the Courant Number. This results - in my case - to a time step size of about 0.0033s which is fairly low.
On the other hand, you can select time steps taken by the solver: "Free". This means implicit time stepping (?). This runs quite well and i get convergence.
So my question is: what is best: Time stepping based on "5*dt_cfl_g1_chns" or "Free"?
Any ideas? Suggestions? Doubts? Experience?
Thanks in advance!
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September 5, 2010 8:42pm UTC in response to Kai Herbrig
Re: CFD time stepping: CFL vs implicit
Hi,
It depends on what you're looking for. If you don't want to miss any detail of the flow (as mush as possible), you should stick to CFL. An example is vortex streets. If you set your time solver to Free it will jump over the vortexes and you won't see them forming. If it is just a simple heat transfer, then free should do it.
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September 7, 2010 11:31am UTC in response to Danial Tz
Re: CFD time stepping: CFL vs implicit
Hi Danial,
thanks for replying.
I think you're right! :) Right now, I'm using "Free".
Best regards
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