CFD Online Logo CFD Online URL
Home > Forums > CFX

decay of turbulence intensity

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

LinkBack Thread Tools Display Modes
Old   September 3, 2008, 11:37
Default decay of turbulence intensity
Posts: n/a
I am doing the transition modelling in CFX, and i got the info on turbulence intensity decay from the inlet to leading edge. I am trying to estimate it, and then I found the equation in CFX manual is not correct? any one have ever tried it? please give me some idea on it? thanks in advance.

The reason I try this is I am doing transition modeling on simple flat plate. I get over-predicted Rex number and I think it may because the turbulence intensity is too low around leading edge area (I checked it, it is about 0.045%). the inlet intensity I st is 10%, So I want to estimate the inlet intensity from prescribed intensity.

another question is as I checked the turbulence intensity from the result and I found the value on inlet boundary is 1% rather 10%, is that all right? Is it supposed to be the initial value 10%

thanks for your any idea!
  Reply With Quote

Old   September 3, 2008, 12:43
Default Re: decay of turbulence intensity
John S.
Posts: n/a
What's the viscosity ratio at your inlet? If it's really high (>100) wallshear can dominate the near-wall flow and cause the turbulence intensity to decay rapidly. If it is high you can try specifying values for intensity (.10 for 10%) and viscosity ratio (should be ~1-10 at the inlet).
  Reply With Quote

Old   September 4, 2008, 05:49
Default Re: decay of turbulence intensity
Posts: n/a
in my case, intensity is 10%, and viscosity ratio is 10. But my inlet is really far from the leading edge (15 times of length of flat plate). I think that will cause great decay of the inlet intensity. So I want to estimate the inlet intensity using the prescribed value in leading edge area, but I found the equation in CFX manual is not correct, it is not a decay formular but a increment one.

thanks for your reply
  Reply With Quote

Old   May 16, 2014, 16:44
Join Date: Dec 2013
Posts: 33
Rep Power: 5
guxin7005 is on a distinguished road
Hi, littlelz

I met the same question you have in CFX. I draw several lines from the inlet to leading edge, sometimes the turbulence intensity decay, sometimes it increase. However, in FLUENT,those lines have the same the turbulence intensity distribution from inlet to leading edge.

How did you solve it in the end?
guxin7005 is offline   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
Turbulence postprocessing Mohsin FLUENT 2 October 3, 2016 14:18
Question on Turbulence Intensity Eric FLUENT 1 March 7, 2012 05:30
About Turbulence Intensity (Pipe flow assimilated) gRomK13 Main CFD Forum 1 July 10, 2009 03:11
Discussion: Reason of Turbulence!! Wen Long Main CFD Forum 3 May 15, 2009 09:52

All times are GMT -4. The time now is 06:23.