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November 1, 2015, 16:57 
Is the convergence of solution ok?

#1 
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Aja
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Hi,
I am simulating an by using Fluent. The convergence of solution is monitored by checking the residuals of the numerically solved governing equations. Moreover, in order to judge the convergence, the behaviour of other quantities, such as the total pressure at the inlet and outlet boundaries, and torque coefficient generated by the rotor, are also monitored. Here, the default convergence criterion of each residual is reduced in order to allow the monitored quantities to stagnate at consistent values. Now, according the following figures, Is the convergence of solution ok? and particularly about residuals? Last edited by aja1345; November 13, 2015 at 09:49. 

November 2, 2015, 06:08 

#2 
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I am unable to see your images. But I can suggest that don't just go by the scaled residuals. Other than that, it is also important to check the flux imbalance. Go to Reports and Fluxes. For convergence, the imbalance in fluxes should be less than 0.2% of the net flux through the domain.


November 2, 2015, 06:34 

#3  
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Aja
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Quote:
First, My English language is not good. I will correct these figure. some questions: Therefore,according to your statement, one of convergence considerations is, checking mass imbalance. in other words, i should check this until i understand that solution converge or not. Am I right? According to the following link, i understood that mass imbalance is equal to absolute value of (inlet massoutlet mass). but How mass imbalance is computed as a percentage? http://www.cfdonline.com/Forums/flu...tml#post571301 

November 2, 2015, 06:39 

#4 
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Other figures:


November 2, 2015, 07:40 

#5 
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Aja
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According to the following figure, Is this such scaled residuals logical?


November 3, 2015, 02:06 

#6 
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Fluxes reported are with signed conventions. So you don't have to do any subtraction. Just note the "Net Results" which is your imbalance. It takes care of how much flux comes in (+ve flux) and how much is going out( ve flux).
Then to calculate percentage: ( (Net Result)/(Inlet Flux) ) *100 should give you the percentage imbalance and it should be less 0.2. 

November 4, 2015, 03:50 

#7  
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Aja
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Quote:
Why do you say that it should be less 0.2? Do you can present a paper and link about this value? 

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