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

Compute Skin friction coef by hand

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 7, 2006, 11:56
Default Compute Skin friction coef by hand
  #1
Francois
Guest
 
Posts: n/a
Hi all,

I'm looking at the detachment point of a boundary layer over a rotating cylinder with the distribution of the Skin Friction Coefficient on the cylinder.

I've just discover that the Skin Friction Coefficient Cf in Fluent is given in absolute value (always >= 0).

So I manage to compute my own skin friction coefficient

Cf= tau_w / (1/2 * rho * U0^2) with tau_w= mu*du/dy |wall

using Custom field fubnction with:

viscosity-lam * dx-velocity-dy / (0.5 * density* U0^2)

where U0 is my freestream velocity.

But when I plot the distribution (on the cylinder) of the skin friction coef given by Fluent and computed by the custom field function ther are differences. I'm surprised that the results are sometimes different.

The definition of the derivatives is not the same when using Custom Field function ? How to explain those differnces ?

Thank's for your suggestions. Francois
  Reply With Quote

Old   February 10, 2006, 07:21
Default Re: Compute Skin friction coef by hand
  #2
Francois
Guest
 
Posts: n/a
Well done François !

I think It will be beter with this custom field function: viscosity-lam * dtangential-velocity-dradial-coordinate / (0.5 * density* U0^2)

SO if there is any guru here ... how to compute this derivative: d Utheta / dr <-> dtangential-velocity-dradial-coordinate

Thanks for you help

François

  Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Skin Friction and Shockwave evaluate problem mosessitio FLUENT 0 May 21, 2011 04:21
Skin Friction and Shockwave evaluate mosessitio FLUENT 0 May 20, 2011 21:30
Skin friction in fluent is wrong syler3321 FLUENT 2 March 24, 2011 09:05
drawing curved line,plotting skin friction lines Alex FLUENT 1 November 17, 2005 08:16
Skin friction J.Cooper FLUENT 1 March 5, 2001 14:33


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