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

Solver fails with compressible flow

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 25, 2006, 09:13
Default Solver fails with compressible flow
  #1
Eric
Guest
 
Posts: n/a
Hi! I use CFX 10 with the option of compressible flow. So I set my density as a function of the pressure. My first question is: can I set the density with something else than "pabs" (p, solver pressure...?). And then, the solver fails when I use a formula of the form rho=f(pabs^2,pabs) and doesn't with a formula of the form rho=f(pabs). Doesn't someone knows why?? Thanks,

Eric
  Reply With Quote

Old   January 29, 2006, 18:26
Default Re: Solver fails with compressible flow
  #2
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

Does it diverge or some other error? Getting a converged solution with an exotic equation of state (EOS) is difficult, you will need very small timesteps.

Glenn Horrocks
  Reply With Quote

Old   January 30, 2006, 11:02
Default Re: Solver fails with compressible flow
  #3
Eric
Guest
 
Posts: n/a
Hi Glenn,

I got a convergence when I set a linear law for the density. But when I set a parabolic law, it diverges first with those kind of error message:

| ****** Notice ****** | | While evaluating Static Enthalpy, | | Static Pressure on boundary upwall | | went outside of its upper limit. Its maximum value was | | 8.6234E+20. The bounds error was handled by clipping. | | If this situation persists, consider increasing the table range.

And then it fails with this error message:

| ERROR #004100018 has occurred in subroutine FINMES. | | Message: | | Fatal overflow in linear solver.

I tried to increase the table range but it's still the same... Do you (or someone alse) have some advise for me to avoid that? Regards,

Eric
  Reply With Quote

Old   January 30, 2006, 18:05
Default Re: Solver fails with compressible flow
  #4
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

The root of the problem is almost certainly to do with the enthalpy/pressure error first mentioned. Sounds like the simulation is diverging. Do a run and stop it before it crashes and have a look in CFX-Post. You will probably find a region of flow which is producing rediculous results and that will be source of the problem.

Glenn Horrocks
  Reply With Quote

Old   February 4, 2006, 09:28
Default Re: Solver fails with compressible flow
  #5
Neale
Guest
 
Posts: n/a
Eric,

If you are using a CEL or User FORTRAN for the equation of state the flow solver internally generates tables for h(T,p) and s(T,p). One thing to make sure is that the table generation limits match what you expect to happen for your case. The default limits are 0.01 bar to 10 bar and 100 to 5000 K.

Neale
  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
compressible flow calculation error using rhoSimpleFoam solver student4326 OpenFOAM 6 February 10, 2012 10:36
Solver for an incompressible, turbulent flow with heat transfer tH3f0rC3 OpenFOAM Running, Solving & CFD 6 March 24, 2011 06:41
help with compressible flow BC's (need subsonic flow) meangreen Main CFD Forum 5 July 24, 2010 13:16
Creating New Solver: For particle-laden compressible jets sankarv OpenFOAM 0 April 4, 2010 18:06
low speed compressible flow lily CFX 2 November 16, 2005 06:15


All times are GMT -4. The time now is 08:48.