CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS

Natural Convection Boundary Conditions, tips or advise needed !

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

Like Tree1Likes
  • 1 Post By Logan Page

LinkBack Thread Tools Search this Thread Display Modes
Old   September 27, 2010, 18:44
Default Natural Convection Boundary Conditions, tips or advise needed !
Logan Page
Join Date: Sep 2010
Posts: 38
Rep Power: 11
Logan Page is on a distinguished road

I am masters engineering student and I'm currently trying to recreate the first part of results from a journal article: "Constructal multi-scale cylinders with natural convection" by T. Bello-Ochenda and A. Bejan, in FLUENT.

Simple put its a row of parallel, horizontal, cylinders (diameter Do) with a constant wall temperature (Tw) cooled by natural convection analyzed in 2D.

The current computation domain that i have setup for FLUENT is made up of:
1) a symmetry plane/edge on the left cutting through the middle of a cylinder
2) a symmetry plane/edge on the right cutting through the middle of the spacing (So) between 2 of the cylinders
3) a pressure inlet at the bottom edge (P = 0, T = 0)
4) a pressure outlet at the top edge (P = 0, T = 0)
5) and a cylinder wall (no slip, no penetration, Tw = 1)

The governing equations have been non-dimentionalised and the input parameters for a Rayleigh Number of 1000 for FLUENT are as follows:
- Do: 1
- Fluid density: 37.268 (boussinesq approximation)
- Fluid Cp: 0.72
- Fluid thermal conductivity: 1
- Fluid viscosity: 1
- Fluid thermal exp. coeff.: 1
- Operating pressure: 0
- Gravity: -1 (Y dir)
- Operating temp.: 0
- Specific operating density: 37.268

Using this model, FLUENT converges nicely for a given upstream (Hu) and downstream (Hd) length from the cylinder, but when i do a grid independence study i find that as i increase the downstream length (Hd) the heat transfer density rate continues to increase (ie there is a chimney effect created).

Does anyone have any suggestions / ideas on how to modify the boundary conditions to eliminate this effect?
montazar likes this.
Logan Page is offline   Reply With Quote


boundary conditions, cylinders, natural convection

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
CFX doesn't continue calculation... mactech001 CFX 6 November 15, 2009 21:25
Natural Condition Boundary Conditions Felix FLUENT 5 January 26, 2007 22:30
Natural Ventilation Boundary conditions lmitsc FLUENT 0 October 2, 2006 12:24
boundary conditions for natural ventiliation room tong FLUENT 0 January 14, 2006 07:33
Natural convection and periodic boundary layer George Thomas FLUENT 0 August 29, 2005 11:12

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