k-e model

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

 December 19, 2010, 03:44 k-e model #1 New Member   Join Date: Nov 2010 Posts: 7 Rep Power: 8 Hi. I want to make a simulation for a airfoil for i solute it with FLUENT. I must use the k-e turbulent model but i do not know how i make the mesh near the wall of airfoil. I have read that the Y plus of first cell must be within 30-300 for standard wall function. However, How can i compute the Y length of cells for i make the mesh arround the foil （NACA0012），and also ,I want some tutorials about ernal flow around airfoil or cylinder with Reynolds number at nearly 50000. Thanks

December 19, 2010, 05:36
#2
New Member

Alexey
Join Date: May 2009
Location: St.Petersburg, Russia
Posts: 23
Rep Power: 9
Quote:
 Originally Posted by MANFEIZHANG Hi. I have read that the Y plus of first cell must be within 30-300 for standard wall function. However, How can i compute the Y length of cells for i make the mesh arround the foil （NACA0012）
First, evaluate drag coeff as , where L is the chord length.
Then calculate friction stress and friction velocity

Then we have
where is the kinematic viscosity

Last edited by ignat; December 19, 2010 at 07:07.

 December 24, 2010, 04:55 #3 New Member   Join Date: Nov 2010 Posts: 7 Rep Power: 8 thanks,ignat now ,i had done some examples by k-e model ,y+=0.0001m,Angle of Attack is 12(re=50000,the chord length is 1m),but from the result ,i can't find the shedding vortex,may i have your email ? i have some details to talk with you，ok？ looking forward to your reply .merry christmas

December 24, 2010, 08:27
#4
New Member

Alexey
Join Date: May 2009
Location: St.Petersburg, Russia
Posts: 23
Rep Power: 9
Quote:
 Originally Posted by MANFEIZHANG y+=0.0001m
y+ is dimensionless parameter. What does it mean "m"?
May be it is dimension value?

Optimal y+ near the wall is about 1 (dimensionless!) for calculation without wall function and 10-100 for calculation with wall functions. But never 0.0001!
Did you estimate friction velocity u* for your case?

I am not expert in aerodynamics but i think shedding vortex does not obligatory occur. It depends on many circumstances.

regards.

 Tags k-e y plus

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post karananand Main CFD Forum 1 February 26, 2010 05:41 Michiel CFX 12 January 25, 2010 04:20 wanglong FLUENT 2 November 26, 2009 00:27 Tim CFX 1 October 7, 2009 06:19 gravis Main CFD Forum 0 October 2, 2009 10:27

All times are GMT -4. The time now is 10:49.