CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

BCs compatibility modified simpleFoam

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 16, 2013, 11:18
Arrow BCs compatibility modified simpleFoam
  #1
Member
 
James
Join Date: May 2013
Posts: 63
Rep Power: 3
Tensian is on a distinguished road
Hi OF community,

I am triying to make the simulations of a complicated channel using simpleFoam, adding temperature equation as stated in somewhere in this forum (I don remember where, but it was something like tutorial "how to add temperature to icoFoam").

The geometry consists in two inlets, an outlet and a wall.

When I started with simulations I found that if I set "fixedValue" for inlets (293 K), outlet (304 K) and wall (306 K), then when I postprocess results I saw something strange near the outlet (some cold zones with no physcal meaning, because in this place the fluid should have been conditioned to hotter temperatures, at least 304 K I guess due to the BC imposed at wall and outlet).

Due to this issue, I changed the BC at outlet and I set it as "zeroGradient". With this change the results are physically correct.

My question is why the first set up is wrong?FLUENT does not give any problem, in addition, it specifies temperature by default if user does not do it (I guess).
Anybody knows if these BCs are adequate?Or maybe the problem is the mesh? (the same mesh gives good results with the second setup and I have tried several meshes, always with the same results when I use fixedVale at outlet). I guess that implementation of solver simpleFoam with temperature is OK, but if it's needed I can post it.

I attach two pictures that should ilustrate my problems.

Best regards and thanks in advance for all answers,

James
Attached Images
File Type: jpg temperaure_fixedValue_outlet.jpg (18.5 KB, 6 views)
File Type: jpg temperaure_zeroGradient_outlet.jpg (18.4 KB, 7 views)
Tensian is offline   Reply With Quote

Old   September 16, 2013, 13:59
Default
  #2
Member
 
Frank Ubber
Join Date: Aug 2013
Posts: 32
Rep Power: 2
kornickel is on a distinguished road
I think your first setup doesn't work out because it's physically not correct. You can't tell the solver which temperature to have at the outlet if you already did it at the inlet since the outlet temperature is depending on the inlet temperature. Same as pressure, velocity etc...

Correct me if I'm wrong
kornickel is offline   Reply With Quote

Old   September 16, 2013, 14:52
Default
  #3
Member
 
James
Join Date: May 2013
Posts: 63
Rep Power: 3
Tensian is on a distinguished road
Thanks for the answer, but I am not sure about what you say...FLUENT allows to specify temperature on every zone with BC asigned. It doesn´t look phisically meaningless for me...
Tensian is offline   Reply With Quote

Old   September 26, 2013, 06:18
Default
  #4
Member
 
James
Join Date: May 2013
Posts: 63
Rep Power: 3
Tensian is on a distinguished road
Hi Frank,

I have been talking with other engineers and they agree with you. No temperature should be imposed at outlet, it has to be calculed by the solver based on the inlet and wall temperature of fluid.

Thanks!
Tensian 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
interFoam vs. simpleFoam channel flow comparison DanM OpenFOAM Running, Solving & CFD 11 January 5, 2013 06:21
Dealing with BC's in OF 1.6 vkrastev OpenFOAM Running, Solving & CFD 5 September 4, 2012 11:58
How to setup cyclic BCs in simpleFOAM hhuang84 OpenFOAM Running, Solving & CFD 12 July 16, 2012 07:01
Help with simpleFoam spsb OpenFOAM 3 February 24, 2012 09:07
Own boundary condition modified simpleFoam erorr in parallel execution sponiar OpenFOAM Running, Solving & CFD 1 August 27, 2008 09:16


All times are GMT -4. The time now is 09:30.