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

Entrainment boundary conditions in a natural convection model

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 27, 2017, 09:47
Default Entrainment boundary conditions in a natural convection model
  #1
New Member
 
Eddie
Join Date: Feb 2017
Location: Copenhagen, Denmark
Posts: 5
Rep Power: 9
emat is on a distinguished road
Hello,

I am trying to model the heat dissipated from a hot body, in still air, by natural convection. I am using snappyHexMesh and chtMultiRegionFoam to create a 2-region conjugate heat transfer model (air and pipe), and appear to have successfully run the model in the case where the hot body is sitting in an enclosed air space.

But what I would really like to do is configure the boundary conditions of the air space so that it is not enclosed. I would like the air to be entrained by buoyancy forces, resulting in it entering from the bottom and exiting at the top.

In the user guide section "5.2.3.2 Entrainment boundary conditions", it is explained that such entrainment conditions are "extremely common". Unfortunately I can't seem to get it working in my model, using a configuration similar to that applied in the damBreak tutorial, and I can't find a tutorial that more closely ressembles this heat transfer situation.

The attached case file (entrainedSnappyMultiRegionHeater.tar.gz) actually runs, but the results look unlikely. Velocities pointing in horizontal directions, and impossibly high heat transfer to the surrounding air. Would anyone be willing to take a look at it and suggest where I've gone wrong?

Many thanks for any suggestions,

Eddie

EDIT: I double-checked that the problem is indeed coming from my entrained inlet/outlet boundary conditions, by enclosing the air space with walls and making the space taller. The results from this are a lot closer to what I would expect. So the problem definitely stems from my use of "totalPressure" and "pressureInletOutletVelocity". Case files for this enclosed version attached (enclosedSnappyMultiRegionHeater.tar.gz).
Attached Files
File Type: gz entrainedSnappyMultiRegionHeater.tar.gz (8.0 KB, 2 views)
File Type: gz enclosedSnappyMultiRegionHeater.tar.gz (8.0 KB, 3 views)

Last edited by emat; March 27, 2017 at 11:30. Reason: Addition of further information, added below "EDIT" line.
emat is offline   Reply With Quote

Old   March 28, 2017, 09:37
Default
  #2
New Member
 
Eddie
Join Date: Feb 2017
Location: Copenhagen, Denmark
Posts: 5
Rep Power: 9
emat is on a distinguished road
My question doesn't seem to have attracted much interest! That's ok. Would anyone have any suggestions on how I might go about troubleshooting this myself? I don't have an error message as such, so it's a bit difficult to start researching where I've gone wrong.
emat is offline   Reply With Quote

Reply

Tags
chtmulitregionfoam, entrainment, heat exchange, open foam, snappy hex mesh

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
sliding mesh problem in CFX Saima CFX 46 September 11, 2021 08:38
Centrifugal fan j0hnny CFX 13 October 1, 2019 14:55
mass flow in is not equal to mass flow out saii CFX 12 March 19, 2018 06:21
Difficulty In Setting Boundary Conditions Moinul Haque CFX 4 November 25, 2014 18:30
Low Mixing time Problem Mavier CFX 5 April 29, 2013 01:00


All times are GMT -4. The time now is 05:11.