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Zaktatir November 2, 2011 06:19

I found out that uncontrolled big imbalances (continuity or momentum equations) may lead to physical instability and therefore for example to another flow regime (especially in multiphase flow-parallel computing).

Can anyone agree to that or tell me about such an experience.


ghorrocks November 2, 2011 21:55

Yes, if a simulation is far from converged, or even worse diverging, the results could be anything. Including being in completely the wrong flow regime.

Zaktatir November 3, 2011 03:19

Yes i agree. Nevertheless for mass transfer or heat transfer it will be hard to stay under 1% for the conservation target...

ghorrocks November 3, 2011 04:57

Some simulations are hard to get the imbalances to converge. Often these are simulations with big variations in time scales - the short time scales are converged but the longer time scales take lots of iterations to converge.

Zaktatir November 3, 2011 05:08

yes in fact, the simulation will be expensive. :mad:

ghorrocks November 3, 2011 06:22

That's right. Simulations with a large range of any scale are difficult - length (very big sections going to very small sections), time (long and short time constants), or anything else.

Zaktatir November 3, 2011 08:40

It was irritating me the fact that even the support did not know or gin out the problem, it is clear that numerical imbalance lead to physical insatiability but i have not thought that it artifacts the results dramatically.

Now i am trying to build new accurate test case

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