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

Distinguish the 'Cd' for Aircraft and Car !

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

Like Tree1Likes
  • 1 Post By truffaldino

Reply
 
LinkBack Thread Tools Display Modes
Old   December 16, 2011, 00:33
Default Distinguish the 'Cd' for Aircraft and Car !
  #1
New Member
 
Irshad
Join Date: Dec 2009
Location: Bangalore
Posts: 20
Rep Power: 7
Irshad22 is on a distinguished road
Why do we consider wetted surface area for aircraft and frontal area for car while calculating the Coefficient of drag? My question is why shouldn't we consider the frontal area in A/C aerodynamics?
Irshad22 is offline   Reply With Quote

Old   December 16, 2011, 03:56
Default
  #2
Senior Member
 
truffaldino's Avatar
 
Join Date: Jan 2011
Posts: 236
Blog Entries: 5
Rep Power: 8
truffaldino is on a distinguished road
Because wings (and airplane in general) change their angle of attack and shape (control surfaces), thus changing frontal area while unchanging wetted area. While a car does not go at different angles of attack and it does not move control surfaces, so its frontal area is unchanged.

Also for aeroplanes one uses planform or wetted area as a refence area for the lift coefficient (as using frontal area for this purpoce makes little sence, since it changes), so we have to use the same reference area for drag.

Truffaldino
f-w likes this.
truffaldino is offline   Reply With Quote

Old   December 16, 2011, 14:03
Default
  #3
Senior Member
 
truffaldino's Avatar
 
Join Date: Jan 2011
Posts: 236
Blog Entries: 5
Rep Power: 8
truffaldino is on a distinguished road
I have also forgot to say that in the case of car the main contribution to drag comes from pressure rather than from skin friction, due to severe flow separation (because of cars non-streamlined shape): This why wetted area plays much smaller role, and frontal area is more important in the case of car.
truffaldino is offline   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
Car park ventilation and impulse fans guillaume Phoenics 8 February 8, 2013 02:29
Car park ventilation and impulse fans guillaume Main CFD Forum 12 June 27, 2011 11:16
Car park ventilation and impulse fans guillaume CD-adapco 0 May 11, 2008 20:00
Car park ventilation and impulse fans guillaume CFX 0 May 11, 2008 19:59


All times are GMT -4. The time now is 23:34.