Time Averaging in OpenFoam

Tarak · November 1, 2010, 14:14

Hii,,

Can someone please tell how to get time averaged velocity, pressure field in LES in OpenFoam.

Thaning You,
Tarak

kalle · November 2, 2010, 02:17

Hi!

Have a look at the pitzDaily tutorial (OF 1.6):

tutorials/combustion/XiFoam/les/pitzDaily

and check how the system/controlDict is written...

Good luck!

Tarak · November 2, 2010, 15:39

Hii,

Thanks for the reply. I went through the code and in fieldAverage.H i'm pasting some lines from it:

00039 // Whether to perform a clean restart, or start from previous
00040 // averaging info if available
00041 cleanRestart true;
00042
00043 // Whether to reset the averaged fields after they have been written.
00044 // Used to average over only the preceding write interval for transient
00045 // cases.
00046 resetOnOutput true;

And these lines are not present in controlDict of my case directory. So can I be sure
that even if I get the solution after multiple runs (i.e restarting in between),
I would be getting the correct time averaged fields?

Thanks,
Tarak

Tarak · November 2, 2010, 16:11

Hii,

I have one more doubt. The problem is that I want to do the time averaging for the fields only for the solutions after it has reached a kind of statistically stationary state. So, I need to ignore the field values of the intial times while calculating the the average.
Can you please offer me a solution for this?

Thanks,
Tarak

Tarak · November 2, 2010, 16:28

Hii,

I think I have a solution to my last post. I need to turn off the option of fieldaveraging in controlDict for the initial time steps, and turn it on (by editing controlDict and restarting) from the moment I want the fields to be averaged. Please comment on this as well as my 2nd post.

Thanks,
Tarak

kalle · November 3, 2010, 02:15

Correct. Don't use the lines in your controlDict until you are ready to start sampling.

2nd post: If you leave your controlDict as it is and leave the UMean, pMean, etc. files in the time directory, they will be read in when you restart.... You can track the number of samples collected in a file found in the /uniform directory located in each time directory.

Good luck!

November 1, 2010, 14:14	Time Averaging in OpenFoam	#1
Tarak Senior Member Tarak Join Date: Aug 2010 Location: State College, PA Posts: 111 Rep Power: 15	Hii,, Can someone please tell how to get time averaged velocity, pressure field in LES in OpenFoam. Thaning You, Tarak

November 2, 2010, 16:28		#5
Tarak Senior Member Tarak Join Date: Aug 2010 Location: State College, PA Posts: 111 Rep Power: 15	Hii, I think I have a solution to my last post. I need to turn off the option of fieldaveraging in controlDict for the initial time steps, and turn it on (by editing controlDict and restarting) from the moment I want the fields to be averaged. Please comment on this as well as my 2nd post. Thanks, Tarak Alhasan likes this.

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November 2, 2010, 02:17		#2
kalle Senior Member Karl-Johan Nogenmyr Join Date: Mar 2009 Location: Linköping Posts: 279 Rep Power: 21	Hi! Have a look at the pitzDaily tutorial (OF 1.6): tutorials/combustion/XiFoam/les/pitzDaily and check how the system/controlDict is written... Good luck!

November 2, 2010, 15:39		#3
Tarak Senior Member Tarak Join Date: Aug 2010 Location: State College, PA Posts: 111 Rep Power: 15	Hii, Thanks for the reply. I went through the code and in fieldAverage.H i'm pasting some lines from it: 00039 // Whether to perform a clean restart, or start from previous 00040 // averaging info if available 00041 cleanRestart true; 00042 00043 // Whether to reset the averaged fields after they have been written. 00044 // Used to average over only the preceding write interval for transient 00045 // cases. 00046 resetOnOutput true; And these lines are not present in controlDict of my case directory. So can I be sure that even if I get the solution after multiple runs (i.e restarting in between), I would be getting the correct time averaged fields? Thanks, Tarak

November 2, 2010, 16:11		#4
Tarak Senior Member Tarak Join Date: Aug 2010 Location: State College, PA Posts: 111 Rep Power: 15	Hii, I have one more doubt. The problem is that I want to do the time averaging for the fields only for the solutions after it has reached a kind of statistically stationary state. So, I need to ignore the field values of the intial times while calculating the the average. Can you please offer me a solution for this? Thanks, Tarak

November 3, 2010, 02:15		#6
kalle Senior Member Karl-Johan Nogenmyr Join Date: Mar 2009 Location: Linköping Posts: 279 Rep Power: 21	Correct. Don't use the lines in your controlDict until you are ready to start sampling. 2nd post: If you leave your controlDict as it is and leave the UMean, pMean, etc. files in the time directory, they will be read in when you restart.... You can track the number of samples collected in a file found in the /uniform directory located in each time directory. Good luck!