
[Sponsors] 
December 7, 2007, 11:24 
Friction Factor

#1 
Guest
Posts: n/a

Hi!
I have calculated the air flow in a some kind of tube. I am now supposed to get the friction factor on the wall. How can I get it? Thanks! 

December 7, 2007, 11:54 
Re: Friction Factor

#2 
Guest
Posts: n/a

the getw command will give you the wall forces. from their you will need to do a little algebra.


December 10, 2007, 05:39 
Re: Friction Factor

#3 
Guest
Posts: n/a

Ok, I see. With GETW I can obtain force, stress, and so on. But there is no friction coefficient... You said I should do a little algebra? I know friction is related to stress but I don't know how to use this.
I don't even know how to use the GETW function, to select my wall, etc. Thanks! 

December 10, 2007, 14:52 
Re: Friction Factor

#4 
Guest
Posts: n/a

It all depends upon the definition you have for friction coefficient.
Use boundary, vertex, and cell sets to look at the wall. Use getw to select the wall force or stress. The commnad "summ cset " will then give you max, min, and average quantities over that wall. Apply your definition & you have friction factor. 

January 1, 2008, 11:36 
Re: Friction Factor

#5 
Guest
Posts: n/a

can anyone define friction factor and use of friction factor


January 4, 2008, 07:47 
Re: Friction Factor

#6 
Guest
Posts: n/a

Friction factor should be the actual flow vs. ideal.


March 9, 2008, 19:35 
Re: Friction Factor

#7 
Guest
Posts: n/a

Hi all,
The friction factor for wall depends only upon Reynolds number if it is laminar flow and depends upon the roughness and the Reynolds number if it is turbulent flow. You have to take length of the computational model almost 20 times of the dia (if it is circular cross section) or hydraulic dia (if it is no circular cross section). In order to calculate friction factor, you have to calculate pressure gradient means pressure difference over a particular length. It is the best to calculate at the end of the geometry near the outlet but 5 to 6 cells before outlet. From the pressur difference and length , hydraulic dia and density (see the formula for friction factor online)you can calculate friction factor. I hope this helps. Sachin 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
How to incorporate the friction factor....  Dewson  FLUENT  0  April 16, 2007 15:03 
plesase help>>>>>>>Friction factor  Mech  FLUENT  0  March 13, 2006 08:57 
Skin friction factor  Ali  FLUENT  2  December 11, 2005 04:25 
friction factor  Sabatini  CDadapco  5  January 27, 2002 10:57 
caculation of friction factor  Dilip  Main CFD Forum  8  May 5, 2001 00:42 