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

Is negative turbulence intensity right?

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

LinkBack Thread Tools Display Modes
Old   April 18, 2006, 10:00
Default Is negative turbulence intensity right?
Posts: n/a
Hi all....

I have doubt about definition of turbulence intensity when I try to compare CFD turbulence profile with my experiment.

TI= u'_RMS(x)/U_mean(x)

Should I take absolute value of U_mean(x) while calculating U_mean(x)? CFD shows reverse flow (negative velocity) at some locations.

Thanks for help.
  Reply With Quote

Old   April 18, 2006, 10:35
Default Re: Is negative turbulence intensity right?
Jonas Larsson
Posts: n/a
Turbulence inensity is always positive.

You should take the absolute value of the mean flow velocity. Check out the CFD-Wiki page on turbulence intensity for a more comprehensive definition. You can find it here:

  Reply With Quote

Old   April 18, 2006, 12:33
Default Re: Is negative turbulence intensity right?
Posts: n/a
Jonas is correct, but I rather say (like in the Wiki information that Jonas added recently) that you should take the speed or norm of the transient averaged velocity vector, i.e. U .

Absolute value of a vector is a generalization and may confuse those not used to it.. I rather say the norm of the velocity vector or speed.

good luck, Opaque.

  Reply With Quote


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
Question on Turbulence Intensity Eric FLUENT 1 March 7, 2012 05:30
channelFoam for a 3D pipe AlmostSurelyRob OpenFOAM 3 June 24, 2011 13:06
BlockMesh FOAM warning gaottino OpenFOAM Native Meshers: blockMesh 7 July 19, 2010 14:11
Axisymmetrical mesh Rasmus Gjesing (Gjesing) OpenFOAM Native Meshers: blockMesh 10 April 2, 2007 14:00

All times are GMT -4. The time now is 16:30.