CFD Online Logo CFD Online URL
Home > Forums > FLUENT

physical velocity formulation and porous media

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

LinkBack Thread Tools Display Modes
Old   June 9, 2003, 11:29
Default physical velocity formulation and porous media
Posts: n/a
Hello Gurus -

I have a 3D sim with a porous bundle zone. The flow regime is laminar at low Reynolds number. I am using the new physical velocity formulation for the porous media in FLUENT6.1 and have had successful (and rapid) convergence under steady state conditions. However, I am unable to get convergence for a time dependent simulation with fixed timestepping. I'm using the segregated solver with PRESTO! pressure interpolation, PISO P-V coupling, 2nd order momentum discretization and 1st order implicit time discretization. All solver parameters (underrelaxation factors and the like) are defaults. I begin from the steady state solution described above and have taken the timestep down to as low as 0.025 seconds - after one or two successful timesteps the residuals blow up. The size of the timestep doesn't seem to be the issue (although I welcome any "enlightenment" from you). Does anyone else have experience with a similar simulation setup or have some suggestions on what might be the problem?

Best regards - Ken
  Reply With Quote

Old   June 10, 2003, 05:42
Default Re: physical velocity formulation and porous media
Posts: n/a
May I knwo what system do you simulate?? e.g. liquid-gas, gas-gas or.....

do you grid size is fine enough??

I have tyr porous media with gas-gas, it seem no divergence problem to me...

but did you check the concentration of you system?? do its tarry with any experimental or theory result??
  Reply With Quote

Old   June 10, 2003, 10:14
Default Re: physical velocity formulation and porous media
Posts: n/a
Ivan -

It's all liquid - the porous media is in place for pressure drop and fluid flow effects. I am not modeling a mixture or multiphase problem at this time.

As for the grid - I achieve rapid convergence with the default solver settings for the steady-state solution so it appears to be fine by that functional metric. I believe the cell skewness and volume limits are ok - its a tet mesh so it ain't perfect, but it does appear adequate.

Comparison with experimental data for the steady state systems has been good with past simulations.

I am basically looking for the time-dependent simulation to converge to the steady state solution or thereabouts after a fair number of timesteps. All models used are the same but the time-dependent simulation diverges even with a very short timestep.

I welcome further comments and thanks for the questions and insight.

Regards - KLG
  Reply With Quote


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
Physical Velocity in Porous Media - FLUENT BUG ??? DH FLUENT 1 August 7, 2012 07:46
Multiphase Porous Media Flow - Convergence Issues VT_Bromley FLUENT 5 March 23, 2011 11:38
Porous formulation visuja FLUENT 0 July 7, 2009 21:37
Discrete phase model in porous media Pradeep FLUENT 0 February 3, 2006 17:30
Physical Velocity !!!! pk FLUENT 0 June 19, 2003 14:22

All times are GMT -4. The time now is 12:35.