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

Isn't the trace of gradU the continuity equation? I need a quantity for elongation

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 9, 2009, 04:04
Default Isn't the trace of gradU the continuity equation? I need a quantity for elongation
  #1
New Member
 
Alex
Join Date: Jun 2009
Location: Erlangen, Germany
Posts: 7
Rep Power: 7
alexey7783 is on a distinguished road
Hi forum users,

I simulated a two phase flow with interFoam and when I compute the "L" tensor (fvc::grad(U)) and take the trace of it (should be du/dx+dv/dy+dw/dz) I don't get zero. I always thought with the finite volume approximation the continuity equation is valid for each single cell?!? Or did I understand something wrong?

The reason is the following. I am looking for a quantity to measure the elongation in my system. As for shear rate it is clear sqrt(2)*mag(symm(fvc::grad(U))) which is the standard definition of shear rate in 3D. But what is it for the elongation rate? I tried to look it up but I can't find a proper definition (Till now I work with sqrt(2)((du/dx)^2+(dv/dy)^2+(dw/dz)^2)

I would be really happy if someone of you could help me

Best regards

Alex
alexey7783 is offline   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
How to write k and epsilon before the abnormal end xiuying OpenFOAM Running, Solving & CFD 8 August 27, 2013 16:33
Convergence moving mesh lr103476 OpenFOAM Running, Solving & CFD 30 November 19, 2007 15:09
IcoFoam parallel woes msrinath80 OpenFOAM Running, Solving & CFD 9 July 22, 2007 03:58
continuity equation Rafal Main CFD Forum 4 November 29, 2006 10:27
Could anybody help me see this error and give help liugx212 OpenFOAM Running, Solving & CFD 3 January 4, 2006 19:07


All times are GMT -4. The time now is 04:21.