Imbalance for convergence

Techies · November 14, 2021, 02:19

We know that 1e-6 is the popular RMS for most convergence cfd, so what about Imbalance(%) ?

ghorrocks · November 14, 2021, 16:36

I rarely use convergence that tight for engineering calculations. So I would not call it "popular".

Convergence tolerance (both residuals and imbalance) should be determined by a sensitivity analysis for your specific case. All cases have different requirements.

But a starting point for the imbalances is 1%. That is in the ball-park most of the time.

Opaque · November 15, 2021, 15:07

Think about an imbalance in relative terms of what you will be missing,

Mass, 1% is 10 gr in 1 kg
Power, 1% is 10W in 1 KW

...

November 14, 2021, 02:19	Imbalance for convergence	#1
Techies Member Mercurial Join Date: Mar 2021 Posts: 72 Rep Power: 5	We know that 1e-6 is the popular RMS for most convergence cfd, so what about Imbalance(%) ?

November 14, 2021, 16:36		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,728 Rep Power: 143	I rarely use convergence that tight for engineering calculations. So I would not call it "popular". Convergence tolerance (both residuals and imbalance) should be determined by a sensitivity analysis for your specific case. All cases have different requirements. But a starting point for the imbalances is 1%. That is in the ball-park most of the time. Opaque likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

November 15, 2021, 15:07		#3
Opaque Senior Member Join Date: Jun 2009 Posts: 1,815 Rep Power: 32	Think about an imbalance in relative terms of what you will be missing, Mass, 1% is 10 gr in 1 kg Power, 1% is 10W in 1 KW ... __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
multiphase flow ，mass and volume fraction imbalance	sope111	CFX	16	September 3, 2018 00:10
Out File does not show Imbalance in %	Mmaragann	CFX	5	January 20, 2017 10:20
Domain Imbalance	HMR	CFX	5	October 10, 2016 05:57
domain imbalance for enrgy equation	happy	CFX	14	September 6, 2012 01:54
Energy imbalance and turbulence	yunhee	CFX	6	February 25, 2008 09:56