CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Bugs

Error in channelOodles tutorial

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 7, 2007, 06:34
Default I found a problem in the chann
  #1
Senior Member
 
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36
alberto will become famous soon enoughalberto will become famous soon enough
I found a problem in the channelOodles tutorial in openFOAM 1.4. The solver runs fine, but the postprocessed data given by postChannel are partially wrong.

As you can see from the plots, the plots of the mean velocity, k, u and uv have the proper shape, but v and w are wrong.









Regards,
Alberto
__________________
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.
alberto is offline   Reply With Quote

Old   June 7, 2007, 06:35
Default Sorry, I forgot the plot of uv
  #2
Senior Member
 
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36
alberto will become famous soon enoughalberto will become famous soon enough
Sorry, I forgot the plot of uv.



A.
__________________
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.
alberto is offline   Reply With Quote

Old   June 7, 2007, 06:48
Default In OpenFOAM-1.4/applications/u
  #3
Senior Member
 
Join Date: Mar 2009
Posts: 854
Rep Power: 22
henry is on a distinguished road
In OpenFOAM-1.4/applications/utilities/postProcessing/miscellaneous/postChannel/readFields.H

replace tensor:: with symmTensor:: and recompile postChannel. This is the corrected version:

readFields.H

Henry
henry is offline   Reply With Quote

Old   June 7, 2007, 08:30
Default Thanks a lot Henry! Alberto
  #4
Senior Member
 
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36
alberto will become famous soon enoughalberto will become famous soon enough
Thanks a lot Henry!

Alberto
__________________
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.
alberto is offline   Reply With Quote

Old   July 16, 2007, 06:00
Default Hello to everyone, how do y
  #5
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
Hello to everyone,

how do you guys estimate Re_tau after running few iterations?
u_tau=(nu*(du_x/dy+du_z/dy))^0.53
Do u use postChannel utility? or there is another utility that calculates these values?

Thanks in advance
Hadi
hadi is offline   Reply With Quote

Old   October 12, 2007, 04:35
Default Hi to all, I have modified
  #6
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
Hi to all,

I have modified readFields.H, and i compared the rms plots for my channel simulation with DNS, i actually get very close results, for urms, Umean and K but the values of vrms and wrms, are equal to the half of the DNS values.
I don't know if it might be an error in postChannel.

Any help will be appreciated.

Hadi
hadi is offline   Reply With Quote

Old   October 19, 2007, 09:35
Default Hi again, sorry for being ann
  #7
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
Hi again,
sorry for being annoying again!

I actually ran periodic channels for Re_tau=395, and Re_tau=180. In openFoam and Fluent.

My U mean profile was good, but rms profiles in openFoam was about 40% off from the DNS values.
In fluent rms profiles was much better!

I was looking to the dimension of R field in the time directory and it is in m/s!?!
I am using version 1.4 is there anything i need to change in the solver?

The graph posted above :uv profile for Re_tau=395 the curve reaches a value of -3e-05, the DNS value is -5.1e-05!

Any help will be appreciated
Hadi
hadi is offline   Reply With Quote

Old   October 22, 2007, 06:09
Default These are Umean and vrms profi
  #8
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
These are Umean and vrms profiles, using classic smagorinsky in openFoam and Fluent for Re_tau=395.
In fluent the averages was calculated over a line.
Obviously there is a problem in my rms profiles.
i am using version 1.4,
Could anyone please tell me what might be the problem? is it related to the Reynolds stress tensor as i mentioned above?

Any help will be appreciated
Hadi



hadi is offline   Reply With Quote

Old   October 22, 2007, 14:37
Default Are you running with the Crank
  #9
Senior Member
 
Join Date: Mar 2009
Posts: 854
Rep Power: 22
henry is on a distinguished road
Are you running with the Crank-Nicholson ddt scheme?
henry is offline   Reply With Quote

Old   October 23, 2007, 04:44
Default Hello Henry, Thank you for
  #10
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
Hello Henry,

Thank you for your reply.
I am using backward ddt scheme.

The wall shear stress velocity(related to the pressure gradient at the wall) is more underestimated in openFoam than in Fluent.
I think i should normalize the rms of U by u_tau, instead of Ubulk, this should give better results.
right?

hadi
hadi is offline   Reply With Quote

Old   October 23, 2007, 05:44
Default In the publications we have pr
  #11
Senior Member
 
Join Date: Mar 2009
Posts: 854
Rep Power: 22
henry is on a distinguished road
In the publications we have produced on the subject, e.g. "Large-eddy Simulation of Turbulent Channel Flows" in Turbulent Shear Flows 11, we normalized with u_tau to be consistent with the DNS data we were comparing with. Are you running both codes with a fixed flow-rate as channelOodles is setup to do?
henry is offline   Reply With Quote

Old   October 23, 2007, 06:02
Default Yes, i am using the same confi
  #12
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
Yes, i am using the same configuration in both calculations, i fixed a constant flow rate, in openFoam, the mean utau is about 10% off from the DNS value for smagorinsky without vanDriest, when using vanDriest utau decreases.
And 2.5 % in fluent(classic smagorinsky).
Do u want me to post the variation of utau in both calculation?

Hadi
hadi is offline   Reply With Quote

Old   October 23, 2007, 06:10
Default How are you calculating u_tau?
  #13
Senior Member
 
Join Date: Mar 2009
Posts: 854
Rep Power: 22
henry is on a distinguished road
How are you calculating u_tau?
henry is offline   Reply With Quote

Old   October 23, 2007, 06:28
Default in openFoam: utau=sqrt(gradp*
  #14
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
in openFoam:
utau=sqrt(gradp*delta/rho)
for each time step and then i calculate the mean value during post processing.
hadi is offline   Reply With Quote

Old   October 23, 2007, 12:00
Default I not you are using the backwa
  #15
Senior Member
 
Join Date: Mar 2009
Posts: 854
Rep Power: 22
henry is on a distinguished road
I not you are using the backward ddt scheme in version 1.4, have you applied the bug-fix posted on this bugs list? If not I suggest you use the Crank-Nicholson scheme, apply the fix or better still upgrade to version 1.4.1 which includes this and many other corrections and improvements.
henry is offline   Reply With Quote

Old   October 23, 2007, 12:27
Default I only changed readFields.H in
  #16
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
I only changed readFields.H in postChannel, do i have to change anything in the solver? where can i find the bug list for channelOodles?

I will also try Crank-Nicholson scheme.

Thank you so much for you advices.

Cheers,
Hadi
hadi is offline   Reply With Quote

Old   October 23, 2007, 12:59
Default The bug is in the backward dd
  #17
Senior Member
 
Join Date: Mar 2009
Posts: 854
Rep Power: 22
henry is on a distinguished road
The bug is in the backward ddt scheme in version 1.4 and the fix has been posted on this bugs list and also fixed in 1.4.1 so the easiest thing for you to do would be to upgrade.
henry is offline   Reply With Quote

Old   October 26, 2007, 04:44
Default Hello Henry, Thank you for
  #18
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
Hello Henry,

Thank you for your advices,

I am using CrankNicholson ddt scheme, waiting for the new version to be installed.
The results didn't converge yet but i have better profiles, i also have better values of u_tau.
When using smagorinsky classic the mean utau value is higher than utau in smagorinsky+vanDriest, since at the wall nusgs is different than zero, so do you think when using utau=sqrt(gradp*delta/rho) in classic smagorinsky i am calculating the real value of utau? or the real value is the one calculated in smagorinsky+vanDriest?
Thanks in advance.
Hadi


hadi is offline   Reply With Quote

Old   October 26, 2007, 04:46
Default oops! Sorry for that!!
  #19
Member
 
hadi tartoussi
Join Date: Mar 2009
Location: paris
Posts: 48
Rep Power: 17
hadi is on a distinguished road
oops!
Sorry for that!!
hadi is offline   Reply With Quote

Old   October 26, 2007, 05:01
Default utau=sqrt(gradp*delta/rho) sho
  #20
Senior Member
 
Join Date: Mar 2009
Posts: 854
Rep Power: 22
henry is on a distinguished road
utau=sqrt(gradp*delta/rho) should be appropriate for channel-flow irrespective of the model used and is the way we calculated utau in the TSF11 paper.
henry is offline   Reply With Quote

Reply


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Problems with channelOodles tutorial alberto OpenFOAM Running, Solving & CFD 0 June 5, 2007 10:08
ReconstructPar channelOodles error maka OpenFOAM Post-Processing 6 September 13, 2006 17:16
[OpenFOAM] Error while postprocessing channelOodles tutorial in OpenFOAM 13 alberto ParaView 4 April 13, 2006 06:58
Error Tutorial 7 ? Mathew Siemens 2 July 20, 2000 20:35
tutorial error? K.L.Huang Siemens 5 May 1, 2000 14:20


All times are GMT -4. The time now is 11:37.