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sega January 5, 2009 05:39

Hello again. Thinking about
Hello again.

Thinking about the maxCo entry in controlDict I'm asking myself what this entry is good for if I'm using Euler implicit discretisation for the temporal derivative, which should be unconditionally stable for ALL timesteps.

What is maxCo limiting in this case?
The velocity field?


caw January 5, 2009 08:36

Hi Sebastian, yes, maxCo is
Hi Sebastian,

yes, maxCo is based on the velocity field. The stability is limited by the PISO algorithm, which is stable for Co up to 1 i think. But Co should be lower for interFoam, it should be around 0.25. To overcome this, you can use subtimestepping for MULES. A good choice is maxCo = 0.5 and two subtimesteps for gamma.

Concerning Euler: even if Euler is unconditionally stable, this does NOT mean that it is unconditionally accurate ;-)

Best regards

sega January 6, 2009 05:05

Thank you, Christian. That mak
Thank you, Christian. That makes sense.
Who can tell the correct Co-limit for PISO?

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