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

convergence building fire

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 19, 2006, 05:11
Default convergence building fire
  #1
Stefan
Guest
 
Posts: n/a
Hi,

I'm just a newbee in CFD and I'm trying to model a fire in a building, but I have convergence problems. I use a mechanical outlet for ventilation and passive inlets. Without the fire, flows converge, but when I introduce the fire/smoke, the flows no longer converge: nettsum(R)/pos.sum(R)=1.5%

I use the parameters below. Does anyone have any ideas what could be the problem? And are there any strategies in this? I get the impression the whole field is more or less trial & error, but aren't there some general guidelines/rules of thumb?

kind regards Stefan de Kool

Groups 3, 4, 5 Grid Information

* Overall number of cells, RSET(M,NX,NY,NZ,tolerance) RSET(M,60,104,12,1.000000E-02)

Group 15. Terminate Sweeps LSWEEP = 1000 RESFAC = 1.000000E-03

Group 17. Relaxation RELAX(P1 ,LINRLX, 1.000000E+00) RELAX(U1 ,FALSDT, 1.000000E+01) RELAX(W1 ,FALSDT, 1.000000E-01) RELAX(KE ,LINRLX, 5.000000E-01) RELAX(EP ,LINRLX, 5.000000E-01) RELAX(SMOK,FALSDT, 1.000000E+01) RELAX(TEM1,FALSDT, 1.000000E+01) KELIN = 3

Group 18. Limits VARMAX(P1 ) = 1.000000E+03 ;VARMIN(P1 ) =-1.000000E+03 VARMAX(U1 ) = 1.000000E+03 ;VARMIN(U1 ) =-1.000000E+03 VARMAX(V1 ) = 1.000000E+03 ;VARMIN(V1 ) =-1.000000E+03 VARMAX(W1 ) = 1.000000E+03 ;VARMIN(W1 ) =-1.000000E+03 VARMAX(EP ) = 1.000000E+10 ;VARMIN(EP ) =-1.000000E+10 VARMAX(SMOK) = 2.000000E+00 ;VARMIN(SMOK) = 0.000000E+00 VARMAX(SLEN) = 1.000000E+10 ;VARMIN(SLEN) = 0.000000E+00
  Reply With Quote

Old   February 10, 2006, 09:16
Default Re: convergence building fire
  #2
Mike
Guest
 
Posts: n/a
If you have a fire source, then the density DEN1 will vary rapidly in the vicinity of the fire source, and so you need to STORE(DEN1) and apply linear relaxation on DEN1, say 0.3. It is advisable to set VARMIN(DEN1)=1.E-5 to protect against negative densities during the course of convergence. Likewise you may also need to limit the temperature TEM1 to prevent non-physical values occuring during the run.
  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
Fire & Smoke in Building Jenn FLUENT 5 December 30, 2012 00:15
Flow around building knight008 CD-adapco 4 November 12, 2008 17:44
Building error waynezw0618 OpenFOAM Running, Solving & CFD 1 July 14, 2008 05:54
Convergence in Fire Sim kam FLUENT 0 August 24, 2006 10:46
Fluent tutorial: fire in a building???? suti FLUENT 0 September 3, 2003 21:36


All times are GMT -4. The time now is 18:04.