CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

numerical diffusion in 1D

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

LinkBack Thread Tools Search this Thread Display Modes
Old   July 27, 2005, 17:08
Default numerical diffusion in 1D
Posts: n/a
Hey everyone,

I am wondering something about numerical diffusion - I have a 3D finite volume code that uses the power law discretization for velocity and central differencing for diffusion. For time stepping, I am marching with rk4.

As a test case, I have given an initial gaussian along the channel, but with uniform concentration across the channel and no flux boundary conditions across the channel. In other words, a 3D code that has been made 1D for testing purposes. My question is this - Should I expect to see any numerical diffusion? I know that upwinding causes it, and I believe that power law does as well because it too is first order. However, I thought that it only appeared when the flow is diagonal to the grid. I have simply given an axial velocity of 1, and diffusion=0, to see if I can make this gaussian advect. It does, but it also diffuses. The code is perfectly conservative, so I don't think losing concentration to the walls is the problem.

Should I expect this? Any possible solutions that would still allow me to keep my power law scheme?

Thanks! Jon
  Reply With Quote

Old   July 30, 2005, 08:14
Default Re: numerical diffusion in 1D
Posts: n/a
I think numerical diffusion is possible in multidimensional problems only.
  Reply With Quote

Old   July 31, 2005, 23:58
Default Re: numerical diffusion in 1D
Posts: n/a
Numerical diffusion can and does occur in 1D. If you look at all the classic mathematical descriptions, the analyses are almost always 1D.
  Reply With Quote


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
Moving mesh Niklas Wikstrom (Wikstrom) OpenFOAM Running, Solving & CFD 122 June 15, 2014 07:20
numerical diffusion in tetrahedral grids Lilly Main CFD Forum 8 May 31, 2011 11:08
Numerical Diffusion in CFX John S. CFX 4 August 17, 2008 20:47
Numerical diffusion. jinwon Main CFD Forum 2 June 27, 2007 12:42
Estimation of numerical diffusion varghese FLUENT 0 March 24, 2003 06:02

All times are GMT -4. The time now is 04:43.