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

ncorr and nNonOrthCorr

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   November 22, 2011, 09:52
Default ncorr and nNonOrthCorr
  #1
Member
 
zakir
Join Date: Nov 2011
Posts: 43
Rep Power: 5
zakir hussain is on a distinguished road
hello everyone

when i am reading the icoFoam.c,I feel confused with it. It said that "include 'readPISOcontrols.H'"and I found the file which defined the number like this:

const int nCorr =
pisoDict.lookupOrDefault<int>("nCorrectors", 1);

const int nNonOrthCorr =
pisoDict.lookupOrDefault<int>("nNonOrthogonalCorre ctors", 0);

I think it doesn't fit very case. my question is how to decide the nCorr and nNonOrthCorr. Are there any relative theories about this? I have read jasak's phd, but I didn't find the answer. Thank you very much.

Best Regards!

zakir
zakir hussain is offline   Reply With Quote

Old   November 25, 2011, 02:53
Default
  #2
Senior Member
 
Nima Sam
Join Date: Sep 2009
Location: Tehran, Iran
Posts: 1,123
Blog Entries: 1
Rep Power: 14
nimasam is on a distinguished road
Send a message via Yahoo to nimasam
whats your mean by "decide the nCorr and nNonOrthCorr" ?
you can define these values in your case directory at system/fvSolution

lookupOrDefault : if you define a value in your fvSolution file then it chooses that value and if you dont define the value, solver considers it as default number
which is 1 for nCorr and 0 for nNonOrthCorr.

usually 2,3 times of corrections are usually enough for piso Algorithm so ( nCorr = 2, 3 ) but for non-orthogonality depends on your mesh and how much non orthogonal it is!
nimasam is offline   Reply With Quote

Old   November 25, 2011, 22:16
Post
  #3
Member
 
zakir
Join Date: Nov 2011
Posts: 43
Rep Power: 5
zakir hussain is on a distinguished road
thanks to nima. I have make clearly about ncorr. I know that the non-orthogonality depends on my mesh,but I don't know what it means "how much non orthogonal it is".Could you please give me a detailed explaination about deciding the nNonOrthCorr on a non-orthogonal mesh?
thank you very much
zakir hussain is offline   Reply With Quote

Old   November 25, 2011, 23:42
Default wallfunction
  #4
Member
 
pooyan
Join Date: Nov 2011
Posts: 62
Rep Power: 5
sam1364 is on a distinguished road
Hi Nima,

I have a question from you.
I am now solving cavity problem in 3D. for turbulence model, I selected RANS and k-epsilon. for wall function, I selected nutkwallfunction. However, I could not find the procedure (how the wall function is defined) used in this type of wall function. I would be grateful if you could tell me what specific wall function is used in nutkwallfunction.

Thanks,
Pooyan



Quote:
Originally Posted by nimasam View Post
whats your mean by "decide the nCorr and nNonOrthCorr" ?
you can define these values in your case directory at system/fvSolution

lookupOrDefault : if you define a value in your fvSolution file then it chooses that value and if you dont define the value, solver considers it as default number
which is 1 for nCorr and 0 for nNonOrthCorr.

usually 2,3 times of corrections are usually enough for piso Algorithm so ( nCorr = 2, 3 ) but for non-orthogonality depends on your mesh and how much non orthogonal it is!
sam1364 is offline   Reply With Quote

Old   November 26, 2011, 06:10
Default
  #5
Senior Member
 
Nima Sam
Join Date: Sep 2009
Location: Tehran, Iran
Posts: 1,123
Blog Entries: 1
Rep Power: 14
nimasam is on a distinguished road
Send a message via Yahoo to nimasam
Quote:
Originally Posted by zakir hussain View Post
thanks to nima. I have make clearly about ncorr. I know that the non-orthogonality depends on my mesh,but I don't know what it means "how much non orthogonal it is".Could you please give me a detailed explaination about deciding the nNonOrthCorr on a non-orthogonal mesh?
thank you very much
i dont know but i think there is no special explanation for it you can find it by try and error
nimasam is offline   Reply With Quote

Old   November 26, 2011, 06:16
Default
  #6
Senior Member
 
Nima Sam
Join Date: Sep 2009
Location: Tehran, Iran
Posts: 1,123
Blog Entries: 1
Rep Power: 14
nimasam is on a distinguished road
Send a message via Yahoo to nimasam
Quote:
Originally Posted by sam1364 View Post
Hi Nima,

I have a question from you.
I am now solving cavity problem in 3D. for turbulence model, I selected RANS and k-epsilon. for wall function, I selected nutkwallfunction. However, I could not find the procedure (how the wall function is defined) used in this type of wall function. I would be grateful if you could tell me what specific wall function is used in nutkwallfunction.

Thanks,
Pooyan
hi dear pooyan
please next time , open new thread or post ur question in related topic
however for k-epsilon look at userguide page-41 or in brief:

Code:
kappa = 0.5U*U*
epsilon = C^0.75 kappa^1.5 / l
C = 0.09
l = characteristic length
nimasam is offline   Reply With Quote

Reply

Tags
nnonorthcorr

Thread Tools
Display Modes

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 On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 03:30.