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

lift/drag coefficient and inertial

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 14, 2007, 02:49
Default lift/drag coefficient and inertial
  #1
zonexo
Guest
 
Posts: n/a
When trying to simulate a pure sinusodial pitching airfoil at high frequency of around 6Hz with amplitude of 30deg, I get cl of amplitude 1000+ and cd of 300+. I wonder if the inertial force has already been included in this value and must been subtracted to get the actual force produced.

I am confused because in some papers regarding wind tunnel experiment with a fruitfly, they mention subtracting the inertial force from the measured force. If so, how should the calculation be done.

Lastly, does the gravity "g" play any part in this question? In my simulation, I did not include the "g" term and the NS eqn has been nondimensioned.

Thanks!
  Reply With Quote

Old   January 14, 2007, 08:57
Default Re: lift/drag coefficient and inertial
  #2
Dominic
Guest
 
Posts: n/a
Hi,

Im pretty sure that the inertial force has been accounted while obtaining the forces. Its true that higher force coefficients are observed for a flapping insect wing such as a bumble bee. I usually dont subtract the inertial forces. For example if u take the case of an implusively accelerated cylinder from rest, the forces that are generated during the initial times are inertial and can be obtained thru a closed form expression based on added mass coefficients. So if one subtracts these forces off, it might not make sense.

If u add 'g', you will have different forces obviously. But thats a different case altoghether.

-Dominic
  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
Inertial and viscous coefficient for porous media franzdrs Main CFD Forum 6 September 15, 2013 23:33
viscous resistance and inertial resistance for microfilter zhhjll FLUENT 1 July 14, 2011 08:55
Porous Media Inertial and Resistance giogio FLUENT 3 June 21, 2011 18:09
viscous and internal resistance coefficient in porous media bansal_vikas1 FLUENT 12 October 6, 2010 08:28
tube bank inertial resistance coefficients Brian FLUENT 0 September 8, 2004 09:04


All times are GMT -4. The time now is 03:43.