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

Free convection

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

Reply
 
LinkBack Thread Tools Display Modes
Old   February 21, 2014, 11:37
Default Free convection
  #1
New Member
 
Michael Leck
Join Date: Feb 2014
Posts: 12
Rep Power: 3
Micha69822 is on a distinguished road
Hey guys,

I try to simulate a verticale plate in the atmosphere. For this case I create a box and on one side I add a small plate. Around I want to have everywhere atmosphere (air). The plate should have an temperature from 333 K and the atmosphere should have 293 K.

However I get always worst results. I think my boundarys are wrong.

Have somebody fixed this issue and can sent me a example case or tell me the right boundarys in the T, U, p_rgh and P file for my plate and the atmosphere?


regards
Michael
Micha69822 is offline   Reply With Quote

Old   March 6, 2014, 06:08
Default Please furnish more details
  #2
New Member
 
Sushanta Sahu
Join Date: Jun 2013
Posts: 2
Rep Power: 0
sengerandu is on a distinguished road
Can you please furnish more details like what is the element size, number, layers, etc?
sengerandu is offline   Reply With Quote

Old   March 6, 2014, 07:31
Default
  #3
New Member
 
Michael Leck
Join Date: Feb 2014
Posts: 12
Rep Power: 3
Micha69822 is on a distinguished road
Hello sengerandu,

thank you for your reply.

My first cell ist 0,014 mm thick and the gradient ist 20.

Now I've changed my case. I have a horizontal zylinder. In the vertical I used a symmetrPlane to reduce my mesh. Also I simulate 2D now.

T-File:
Is on atmosphere "inletOutlet" and on the wall ist "fixedValue".

U-File:
For atmosphere I use "pressureInletOutletVelocity" and for the wall I use "fixedValue".

P-File ist "calculated"


I think there ist a problem with the p_rgh file. Here I tried a lot of values:
fixedValue, fixedFluxPressure, zeroGradient, totalPressure for the wall and atmosphere.
And my flow pattern look like worse!


Best wishes
Michael
Micha69822 is offline   Reply With Quote

Old   March 10, 2014, 11:35
Default
  #4
New Member
 
Join Date: Feb 2014
Posts: 16
Rep Power: 3
cristina is on a distinguished road
Micha69822,

¿did you get your case runnin? You are trying to simulate an open environment aren´t you? So am I, but I dont get any physical results....
It must be the boundary conditions...

Cristina
cristina is offline   Reply With Quote

Old   March 10, 2014, 14:35
Default
  #5
New Member
 
Michael Leck
Join Date: Feb 2014
Posts: 12
Rep Power: 3
Micha69822 is on a distinguished road
Hi,

yes I did.

My failure was the p_rgh File. The bottom has to defined as "totalPressure" and the atmosphere around has to "inletOutlet". The other BC's the same as I described.

And now I get the right solutions!
__________________
Best regards
Michael
Micha69822 is offline   Reply With Quote

Old   March 11, 2014, 06:58
Default
  #6
New Member
 
Join Date: Feb 2014
Posts: 16
Rep Power: 3
cristina is on a distinguished road
Hi Micha69822,

Which solver are you using? buoyantBoussinesqSimpleFoam? I am trying with SimpleFoam, but I do not find the right BC.
I have flow over a ground in atmospheric conditions.... very simple: inlet (constant wind velocity) outlet, sides and Sky and then the ground....
As you recommended, I am using totalPressure in the outet but I dont get good results...
Can you post your BC more detailed? I also attach you my case, maybe you can help me...

thanks!

Cristina
Attached Files
File Type: zip caseAtmosWind.zip (12.2 KB, 7 views)
cristina is offline   Reply With Quote

Old   March 11, 2014, 08:41
Default
  #7
New Member
 
Michael Leck
Join Date: Feb 2014
Posts: 12
Rep Power: 3
Micha69822 is on a distinguished road
Hi cristina,

I can't work with your files because I use OpenFOAM Version 2.3.0.
But I see in your blockMeshDict that you have defined all faces as wall. For atmosphere you need patch but there is a different in the Versions?!
__________________
Best regards
Michael
Micha69822 is offline   Reply With Quote

Old   March 11, 2014, 09:27
Default
  #8
New Member
 
Join Date: Feb 2014
Posts: 16
Rep Power: 3
cristina is on a distinguished road
Hi,

In effect, when I change the BC to patch it does not even run.... I dont know. Can you detail me your BC? So I can try to do the same?

thank!
cristina is offline   Reply With Quote

Old   March 11, 2014, 11:07
Default
  #9
New Member
 
Michael Leck
Join Date: Feb 2014
Posts: 12
Rep Power: 3
Micha69822 is on a distinguished road
Hello cristina,

my settings in the attachment. I hope it help you?

I forgot to tell you my Sovler. I use the buoyantBoussinesqSimpleFoam and the buoyantSimpleFoam.
Attached Images
File Type: jpg Settings.jpg (7.7 KB, 15 views)
__________________
Best regards
Michael
Micha69822 is offline   Reply With Quote

Old   March 12, 2014, 03:20
Default
  #10
New Member
 
Join Date: Feb 2014
Posts: 16
Rep Power: 3
cristina is on a distinguished road
Hi Micha,

¿your bottom is a wall? ¿like the ground?
Cristina
cristina is offline   Reply With Quote

Old   March 12, 2014, 05:55
Default
  #11
New Member
 
Michael Leck
Join Date: Feb 2014
Posts: 12
Rep Power: 3
Micha69822 is on a distinguished road
Hi,

no. I simulate a pipe an this surface is in my case the wall.
__________________
Best regards
Michael
Micha69822 is offline   Reply With Quote

Reply

Tags
atmosphere, natural convection

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
free convection Arun3012 FLUENT 0 February 25, 2013 01:45
Free convection ebrattr Main CFD Forum 6 August 20, 2012 16:05
CFX-5.5 simulating air free convection Dustin Lee CFX 0 April 16, 2003 02:54
Free Convection in STAR-CD George Hampel CD-adapco 0 November 16, 2000 00:38
free convection heat transfer from a heated horizontal surface through a liquid to a thin cooled fin Kaushik FLUENT 1 May 8, 2000 06:47


All times are GMT -4. The time now is 16:03.