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

Size of 3D in 2D problem?

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 6, 2000, 20:49
Default Size of 3D in 2D problem?
  #1
Arthur Valais
Guest
 
Posts: n/a
Hi!

Does anyone know what the third dimension size is in a two-dimensional problem? I need to know as I'm doing some hand calculations to check fluent. Specifically, density = mass / volume, but for the volume I only have x + y.

Bye,

Arthur
  Reply With Quote

Old   March 7, 2000, 10:04
Default Re: Size of 3D in 2D problem?
  #2
Detlef Schulze
Guest
 
Posts: n/a
Hi Arthur, in a 2d flow the z-coordinate in any quantity such as coefficients etc. is usually "per unit depth". Therefore, you should take 1 m (or whichever physical unit you use).

Greetings Detlef

  Reply With Quote

Old   March 7, 2000, 20:15
Default Re: Size of 3D in 2D problem?
  #3
Arthur Valais
Guest
 
Posts: n/a
Thanks.

So looking at the case file it says... grid was created in m. This indicates that for one cell 1cmx1cm, its depth is 100x the other dimension. This is a serious problem. What's worse is that I found no explicit documentation about this.

So, if I want a very thin layer (depth) eg. 1cm do I need to recreate the grid or can I scale it? Or do I need to move to full 3d?

Many thanks,

Arthur Valais

  Reply With Quote

Old   March 7, 2000, 22:08
Default Re: Size of 3D in 2D problem?
  #4
Greg Perkins
Guest
 
Posts: n/a
I'm not sure if I have understood the problem, but I believe, as stated before, Fluent just assumes a unit depth when computing areas, volumes etc. in 2D. This is normal.

Ie. think of these quantities as area or volume per unit depth.

If you are using 2D presumably you're problem can be approximated as 2D - ie. changes/gradients in the third dimension are small compared to those in the other two dimensions which you simulate on a plane. In this case, I don't see any reason to simulate in 3D to get around the conceptual ideas above. On the other hand if its a 3D problem it needs to be solved in 3D....

Let me know what you think!
  Reply With Quote

Old   March 7, 2000, 22:41
Default Re: Size of 3D in 2D problem?
  #5
Arthur Valais
Guest
 
Posts: n/a
Yes, changes in 3d are not significant.

But I wanted to know how to calculate density of a gas I had in a cell, and then it struck me that I didn't know all the dimensions.

So I needed to find out exactly what fluent did to the 3rd dimension (I couldn't make the assumption that it placed 1m into depth because the grid was made in metres).

So if it is 1m depth then the volume of my 1cmx1cm cell is 1e-4 m3.

Thanks,

Arthur Valais
  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
Gambit - meshing over airfoil wrapping (?) problem JFDC FLUENT 1 July 11, 2011 05:59
OF 1.6 | Ubuntu 9.10 (64bit) | GLIBCXX_3.4.11 not found piprus OpenFOAM Installation 22 February 25, 2010 14:43
Phase locked average in run time panara OpenFOAM 2 February 20, 2008 15:37
A 2-different size mesh problem Luc FLUENT 1 January 10, 2003 17:13
Transient Purging Problem Sundar FLUENT 1 June 6, 2002 14:20


All times are GMT -4. The time now is 03:05.