Residuals : Final or 0 ?

Gearb0x · March 23, 2010, 09:00

Hello

to check convergence in openfoam I used the foamJob & foamLog utilities which write data in text files.

In these text files, for each variable of interest I always have two files :
(example for p)
p_0
pFinalRes_0

Which one should I look at for the convergence?
p_0 seems to decrease continually while pFinalRes_0 has jumps

And what are the meaning of these two residuals?

Thanks for the help

Gearb0x · April 10, 2010, 17:45

and what about time step continuity error local, global and cumulatice?

How should they behave? Always above 10^-3 or something? Only the last values after X iterations should be looked at?

Thanks for your help

mohsenkh599 · April 14, 2010, 14:56

hi
how can I visualize the residuals? I wonder if there is a way to see the residuals like the fluent?
thanks

Gearb0x · April 14, 2010, 15:00

you can!

just do like this

solver > log
foamLog log
cd logs
xmgrace -log y -legend load pRes_0

example : simpleFoam log for the solver
(I'm not sure about the name in xmgrace for the variables, just check in the log directory

)

gschaider · April 14, 2010, 15:15

Quote:

Originally Posted by mohsenkh599

hi
how can I visualize the residuals? I wonder if there is a way to see the residuals like the fluent?
thanks

I use http://openfoamwiki.net/index.php/Co...PlotWatcher.py (but I am not neutral)

alberto · April 15, 2010, 01:06

Hehe, I use pyFoam tools too (and I'm neutral

)

Best,

mohsenkh599 · April 17, 2010, 10:40

hi foamers
I have simulated a contraction flow. how can I plot for example velocity or the (tauxx-tauxy) across a line connecting two points in the geometry.
after the simulation at every time there are p, phi, U, tau, tau_0 and etc. files at a folder at that time.
thanks a lot

alberto · April 17, 2010, 13:38

You can plot over lines in paraview. For the stress tensor, you've to first compute it from the fields you stored.

Best,

mohsenkh599 · April 18, 2010, 01:17

hi
thank you very much alberto
but can you possibly explain more? I cant clearly understand your directions
the best

alberto · April 18, 2010, 02:54

To plot over a line, open you case in paraview, show it as usual, then use the "Plot over a line" filter.

To save the stress tensor, use the stressComponents utility after you run the case.

Best,

March 23, 2010, 09:00	Residuals : Final or 0 ?	#1
Gearb0x Senior Member Join Date: Nov 2009 Posts: 111 Rep Power: 16	Hello to check convergence in openfoam I used the foamJob & foamLog utilities which write data in text files. In these text files, for each variable of interest I always have two files : (example for p) p_0 pFinalRes_0 Which one should I look at for the convergence? p_0 seems to decrease continually while pFinalRes_0 has jumps And what are the meaning of these two residuals? Thanks for the help

April 14, 2010, 14:56	request	#3
mohsenkh599 Member mohsen kh Join Date: Nov 2009 Posts: 41 Rep Power: 15	hi how can I visualize the residuals? I wonder if there is a way to see the residuals like the fluent? thanks

April 15, 2010, 01:06		#6
alberto Senior Member Alberto Passalacqua Join Date: Mar 2009 Location: Ames, Iowa, United States Posts: 1,912 Rep Power: 36	Hehe, I use pyFoam tools too (and I'm neutral ) Best, __________________ Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using.

April 17, 2010, 10:40	help	#7
mohsenkh599 Member mohsen kh Join Date: Nov 2009 Posts: 41 Rep Power: 15	hi foamers I have simulated a contraction flow. how can I plot for example velocity or the (tauxx-tauxy) across a line connecting two points in the geometry. after the simulation at every time there are p, phi, U, tau, tau_0 and etc. files at a folder at that time. thanks a lot

April 17, 2010, 13:38		#8
alberto Senior Member Alberto Passalacqua Join Date: Mar 2009 Location: Ames, Iowa, United States Posts: 1,912 Rep Power: 36	You can plot over lines in paraview. For the stress tensor, you've to first compute it from the fields you stored. Best, __________________ Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using.

April 10, 2010, 17:45		#2
Gearb0x Senior Member Join Date: Nov 2009 Posts: 111 Rep Power: 16	and what about time step continuity error local, global and cumulatice? How should they behave? Always above 10^-3 or something? Only the last values after X iterations should be looked at? Thanks for your help

April 14, 2010, 15:00		#4
Gearb0x Senior Member Join Date: Nov 2009 Posts: 111 Rep Power: 16	you can! just do like this solver > log foamLog log cd logs xmgrace -log y -legend load pRes_0 example : simpleFoam log for the solver (I'm not sure about the name in xmgrace for the variables, just check in the log directory )

April 18, 2010, 01:17	help	#9
mohsenkh599 Member mohsen kh Join Date: Nov 2009 Posts: 41 Rep Power: 15	hi thank you very much alberto but can you possibly explain more? I cant clearly understand your directions the best

April 18, 2010, 02:54		#10
alberto Senior Member Alberto Passalacqua Join Date: Mar 2009 Location: Ames, Iowa, United States Posts: 1,912 Rep Power: 36	To plot over a line, open you case in paraview, show it as usual, then use the "Plot over a line" filter. To save the stress tensor, use the stressComponents utility after you run the case. Best, __________________ Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using.

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