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

Wrong operator in transonic pressure equation?

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

Like Tree2Likes
  • 2 Post By Horacio Aguerre

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 6, 2011, 09:45
Post Wrong operator in transonic pressure equation?
  #1
Member
 
Florian Ettner
Join Date: Mar 2009
Location: Munich, Germany
Posts: 41
Rep Power: 17
dohnie is on a distinguished road
Hello,
in my transonic simulations with reactingFoam my local continuity errors are far too high (~0.01).
I've stumbled upon the pressure equation: After the pEqn is solved, the flux is corrected. In the subsonic case:
Code:
        if (nonOrth == nNonOrthCorr)
        {
            phi += pEqn.flux();
        }
In the transonic case:
Code:
        if (nonOrth == nNonOrthCorr)
        {
            phi == pEqn.flux();
        }
Shouldn't the latter "==" operator be replaced by a "+=", too?

If not, who can explain it?
dohnie is offline   Reply With Quote

Old   July 10, 2015, 13:07
Default
  #2
New Member
 
België/Belgique
Join Date: Jul 2015
Posts: 3
Rep Power: 11
David1 is on a distinguished road
I know I am replying on an old post, but have you found your answer?

I have a similar doubt with rhoSimpleFoam, where:
Quote:
phi == pEqn.flux();
in the transonic case and:
Quote:
phi -= pEqn.flux();
for subsonic flow
David1 is offline   Reply With Quote

Old   July 11, 2015, 23:16
Default
  #3
New Member
 
Join Date: May 2013
Location: Santa Fé, Argentina
Posts: 5
Rep Power: 13
Horacio Aguerre is on a distinguished road
Hello Florian,

Note that the method "flux()" is applied over the fvMatrix (pEqn). When solving with the transonic flag in true, the pEqn contains the advective term fvm::div(...). The whole continuity equation is assembled implicity in the pressure equation and then the flux can be calculated with pEqn.flux().

On the other hand, in subsonic cases the advective term is assembled eplicity with fvc::div(phi(or phiHByA)). The last term is not in the pEqn matrix (l.h.s part) and then the advective term must be taken in account to construct the phi flux as phi = phi + pEqn.flux() or phi = phiHByA + pEqn.flux()

hope it helps!
hjasak and David1 like this.
Horacio Aguerre is offline   Reply With Quote

Reply

Tags
coupling, flux correction, transonic

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pressure work term in turbulent K.E. equation lost.identity Main CFD Forum 0 March 8, 2011 13:21
Strcture of pressure correction equation in PISO stable over time ? sebi Main CFD Forum 1 October 26, 2010 23:19
Constant velocity of the material Sas CFX 15 July 13, 2010 09:56
pressure Poisson equation in fractinoal step metho Rui Main CFD Forum 6 October 15, 2000 05:57
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 07:45.