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

boundary condition

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

Reply
 
LinkBack Thread Tools Display Modes
Old   February 17, 2000, 07:37
Default boundary condition
  #1
KIAN
Guest
 
Posts: n/a
At the moment I am using the standard k-e model. But I don't know what turbulent intensity to set at and the scale length too. What about the near wall function, which one to use if I am usinf the k-e model???
  Reply With Quote

Old   February 18, 2000, 18:19
Default Re: boundary condition
  #2
Sung-Eun Kim
Guest
 
Posts: n/a
Please read the User's Guide. It provides an overall guideline on how to set the BCs for turbulent quantities. Yet, it's just a general guideline, and can't tell you much about your specific situation. For instance, you may have a big disturbance just updtream of an inlet boundary on which you want to specify the BCs forturbulent quantities. The, the rule of thumb given in the manual won't help much.

Anyway, it's best to discuss this with your support engineer, if the User's Guide cease to be useful.
  Reply With Quote

Old   February 21, 2000, 05:02
Default Re: boundary condition
  #3
allan thomson
Guest
 
Posts: n/a
If your flow is quite turbulent, say a combustor then a turbulence intensity of 10% is ok, or if it is a wind tunnel type flow then an intensity 1-5% is more likely. If you want to set the length scale then a sort of rule of thumb is to use a length scale which corresponds to about 10% of a charcteristic dimension. Generally I use 10% of the length of the smallest length of the inlet.
  Reply With Quote

Old   February 21, 2000, 05:26
Default Re: boundary condition
  #4
KIAN
Guest
 
Posts: n/a
If my flow type is in a cleanroom, what turbulent intensity will it likely to be???
  Reply With Quote

Old   February 21, 2000, 06:51
Default Re: boundary condition
  #5
allan thomson
Guest
 
Posts: n/a
What you could do if you model does not take long to run is set the inlensity to 0.5% run it then double the value and see if there is any great difference in the flow field, then double it again and so on and keep checking.

It may be easier to measure it though.

I take it that the air inlet will be through a mesh of some sort, use 10% of the mesh size as you length scale.
  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
Boundary Conditions Thomas P. Abraham Main CFD Forum 20 July 7, 2013 05:05
Setting outlet Pressure boundary condition using CAFFA code Mukund Pondkule Main CFD Forum 0 March 16, 2011 04:23
Domain Imbalance HMR CFX 3 March 6, 2011 21:10
How exactly the "pressure outlet" bdry condition compute properties on the boundary? yating9901 FLUENT 3 June 28, 2010 12:26
How to set boundary condition in Fluent for the fo Peiyong FLUENT 1 November 10, 2006 12:44


All times are GMT -4. The time now is 00:55.