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

pressure corrector turbFoam

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 8, 2009, 13:25
Default pressure corrector turbFoam
  #1
New Member
 
Join Date: Jun 2009
Location: Belgium
Posts: 3
Rep Power: 8
Sara D is on a distinguished road
Dear all,

I have a question concerning the pressure correction in turbFoam:

Code:
fvScalarMatrix pEqn
                    (
                        fvm::laplacian(rUA, p) == fvc::div(phi)
                    );
The right hand side is implemented using phi instead of U to avoid an extra interpolation of U to Uf (see http://www.tfd.chalmers.se/~hani/kur...7/rhiechow.pdf).

This confuses me a little bit as I expected the right hand side to be
fvc::div(H/A)=sumOverFaces(Hf/Af.Sf)

and with phi=Uf.Sf and Uf=H/A at this point in the algorithm, I assume the code does the following:
fvc::div(phi)=fvc::div(Hf/Af.Sf)=sumOverFaces(Hf/Af.Sf.Sf)
with one Sf too many

I probably overlook something, can someone tell me what?

Thanks in advance,

Sara

Last edited by Sara D; July 9, 2009 at 03:26.
Sara D is offline   Reply With Quote

Old   July 12, 2009, 13:38
Default
  #2
Senior Member
 
Henrik Rusche
Join Date: Mar 2009
Location: Braunschweig, Niedersachsen, Germany
Posts: 275
Rep Power: 9
henrik is on a distinguished road
Sara,

I think what you are missing is that fvc::div(phi) DOES a simple sum over all cell faces and DOES NEITHER dot-product with the face area vectors NOR interpolate to the face.

Yes, this is not intuitive, but it makes a lot of sense when you think about it.

Unfortunately, on page P-39 the Programmer's Guide says:
Quote:
The fvc::div function can take as its argument either a surface<Type>Field, in which case \varPhi_f is specified directly, or a vol<Type>Field which is interpolated to the face by central differencing as described in Section 2.4.10:
where - I think - it should read:
Quote:
The fvc::div function can take as its argument either a surface<Type>Field, in which case S_f\cdot\varPhi_f is specified directly, or a vol<Type>Field which is interpolated to the face by central differencing as described in Section 2.4.10:
Henrik
henrik is offline   Reply With Quote

Old   July 13, 2009, 03:34
Default thanks
  #3
New Member
 
Join Date: Jun 2009
Location: Belgium
Posts: 3
Rep Power: 8
Sara D is on a distinguished road
Henrik,

Thank you, now I understand.
That is indeed a pitfall and the programmers guide doesn't help in this case.

Thanks a lot for clarifying,

Sara
Sara D is offline   Reply With Quote

Reply

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Neumann pressure BC and velocity field Antech Main CFD Forum 0 April 25, 2006 02:15
Gas pressure question Dan Moskal Main CFD Forum 0 October 24, 2002 22:02
what the result is negatif pressure at inlet chong chee nan FLUENT 0 December 29, 2001 06:13
Hydrostatic pressure in 2-phase flow modeling (CFX4.2) HB &DS CFX 0 January 9, 2000 14:19
Hydrostatic pressure in 2-phase flow modeling (long) DS & HB Main CFD Forum 0 January 8, 2000 16:00


All times are GMT -4. The time now is 17:25.