Conservation of mass

thecfduser · November 11, 2009, 08:16

Hello all,
i am a Fluent user.
We all know that the finite volume method is conservative
however, we can see that in many simulations we have small mass imbalance
Is that due to roundoff errors????
do FVM still conservative for non linear equations like NS?

when the simulation diverge, we can obtain sometimes an enormous mass imbalance....
Thanks for ure replies
Regards

bob12 · November 11, 2009, 16:21

sometimes the convergence criteria there isn't all. for example in the airfol tutorial if i don't remember badly; don't use this criteria but monitor mass flow in the outflow surface. i think that you change this and go on with the interetion the bilance of mass go down.
i hope that will be helpful

thecfduser · November 11, 2009, 20:00

yes it was very useful
thanks comrade

November 11, 2009, 08:16	Conservation of mass	#1
thecfduser Senior Member karine Join Date: Nov 2009 Posts: 158 Rep Power: 16	Hello all, i am a Fluent user. We all know that the finite volume method is conservative however, we can see that in many simulations we have small mass imbalance Is that due to roundoff errors???? do FVM still conservative for non linear equations like NS? when the simulation diverge, we can obtain sometimes an enormous mass imbalance.... Thanks for ure replies Regards

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November 11, 2009, 16:21		#2
bob12 Member Join Date: Oct 2009 Location: Italy Posts: 88 Rep Power: 16	sometimes the convergence criteria there isn't all. for example in the airfol tutorial if i don't remember badly; don't use this criteria but monitor mass flow in the outflow surface. i think that you change this and go on with the interetion the bilance of mass go down. i hope that will be helpful

November 11, 2009, 20:00		#3
thecfduser Senior Member karine Join Date: Nov 2009 Posts: 158 Rep Power: 16	yes it was very useful thanks comrade