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

Question...Turbulence Intensity & Viscosity ratio

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

Like Tree2Likes
  • 2 Post By RoM

Reply
 
LinkBack Thread Tools Display Modes
Old   October 6, 2005, 03:40
Default Question...Turbulence Intensity & Viscosity ratio
  #1
Jay
Guest
 
Posts: n/a
Hi

Is there somebody who could explain the meaning of "Turbulence Intensity, Back flow Turbulcen Intensity and Turbulence Viscosity Ratio"?

I do not know why those are 5% or 10%.

Please give me a tip.

Thanks

  Reply With Quote

Old   October 6, 2005, 04:41
Default Re: Question...Turbulence Intensity & Viscosity ra
  #2
RoM
Guest
 
Posts: n/a
Turbulence intensity is defined as the ratio of the root-mean-square of the velocity fluctuation (u') and the mean flow velocity (u_avg). It can be estimated in terms of Re using equation 7.2-1 from the users guide. A Re number of 5e4 is equal to a turbulence intensity of 4% (according to 7.2-1).

Turbulent viscosity ratio is define as the ratio of the tubulent viscosity (calculated by your tubulence model) and the laminar viscosity (from the material panel). For most fully turbulent flows it will range from 1000 to 1e4.

Backflow parameters are taken by fluent if any backflow occurs during the iteration, otherwise they are not used. A good guess of these parameters will help your solution to run stable if backflow occurs, a (very) bad guess can cause divergence.

Read users guide chapter 7.2.2 "Determening Turbulence Parameters" for more information.

RoM
hossein65 and Anna Tian like this.
  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 define the turbulence intensity and mixing length at an outlet (for k-eps)? david39 OpenFOAM Running, Solving & CFD 6 February 2, 2011 04:01
Discussion: Reason of Turbulence!! Wen Long Main CFD Forum 3 May 15, 2009 09:52
Turbulence viscosity limited Madhukar Rapaka FLUENT 0 June 26, 2006 03:17
significance of viscosity ratio phil FLUENT 15 January 30, 2002 06:39
Turbulence Intensity Vs CFD Simulation Apple L S Chan Main CFD Forum 3 December 15, 1998 18:28


All times are GMT -4. The time now is 13:03.