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February 9, 2013, 13:06 
Problem with residual and their definition!

#1  
Member
Simone
Join Date: Sep 2012
Posts: 95
Rep Power: 6 
Hi guys, I was troubling a little with the definition of the residuals in OF. Following this thread "http://www.cfdonline.com/Forums/ope...dsolvers.html", I've figured out that, at each step, the residual is calculated as follow: (focusing over an hypothetical momentum equation)
Quote:
Then, the normalization factor is calculated as: Quote:
Quote:
Quote:
Finally the residual (normalized, so dimensionless) is: Quote:
My questions are: 1) Is my interpretation correct? 2) Could someone explains what the average function do? I think it makes an average of a field (vector or scalar) in the domain but I'm not really sure 3) How can residual be equal 1 at step 0? 4) At each iterative step (I'm thinking about simpleFoam) the "initial Value" of residual at each time step is the difference between the residual calculated as before at the ith step and the (i1)th step or the first? Thanks in advance Simone 

February 11, 2013, 07:00 

#2 
Member
Simone
Join Date: Sep 2012
Posts: 95
Rep Power: 6 
Any answer guys?


February 14, 2013, 08:36 

#3 
Member
Simone
Join Date: Sep 2012
Posts: 95
Rep Power: 6 
Isn't really anyone that can help me to figure out my problem?


March 27, 2013, 05:56 

#4 
Member
Simone
Join Date: Sep 2012
Posts: 95
Rep Power: 6 
Hi guys I return on this post! I wanted to ask again if there is someone that can explain me if my interpretation of the residuals is correct..in particular I wanted some explanation about the normalization factor that is used..
is it really variable at each iteration or am I wrong? Please someone answers me. Cheers Simone 

April 1, 2013, 11:01 

#5 
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Santiago Marquez Damian
Join Date: Aug 2009
Location: Santa Fe, Santa Fe, Argentina
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Santiago MÁRQUEZ DAMIÁN, Ph.D. Research Scientist Research Center for Computational Methods (CIMEC)  CONICET/UNL Tel: 543424511594 Int. 7032 Colectora Ruta Nac. 168 / Paraje El Pozo (3000) Santa Fe  Argentina. http://www.cimec.org.ar 

July 18, 2016, 10:39 

#6 
Senior Member
Join Date: Jun 2012
Location: Germany, Bochum
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I am wondering why the procedure for normalization is rather complex for the OpenFOAM code. Is there an advantage for the OF normalization type compared to lets say Fluent where we only divide by the l.h.s of the equation sum(A_p*Phi_p)
Is there any text book that somebody can recommend? 

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