Aerodynamics question. Airflow under car?

The place for all technical car discussions. If you haven't already, read our Disclaimer first!

Moderator: The Mod Squad

Aerodynamics question. Airflow under car?

Postby BBBrad » Fri Jul 19, 2013 8:35 pm

I had a search around and cant quite get a definitive answer. I want to know how much air flows under a car while traveling? I know that great effort is put into the front of racecars to lessen airflow under the car. What about your normal street car with 100mm of ground clearance? I know of stories of aw11's with the rear hatch unlocked, and the airflow pushing the lid up and up the faster you go.
So, lots of air? Or not much at all?
My new car...99 mr-s
BBBrad
Toyspeed Member
 
Posts: 324
Joined: Fri May 17, 2002 8:30 am
Location: marton

Postby iOnic » Fri Jul 19, 2013 8:43 pm

Faber est suae quisque fortunae
2009 Mazda3 MPS
2016 CFMoto 650NKs
2013 Hyundai IX35 Highlander
User avatar
iOnic
Toyspeed Member
 
Posts: 3736
Joined: Fri Jun 25, 2004 6:31 pm
Location: Melbourne VIC

Postby KinLoud » Fri Jul 19, 2013 11:24 pm

Generally a road (factory spec) car will get some lift at the front of the car as speed increases.

A vertical air dam below the front of the car reduces airflow under car
- reducing drag (some exceptions)
- reducing lift as speed increases (perhaps creating some downforce)
- increases airflow through radiator.

Refer to Competition Car Aerodynamics by Simon McBeath
Has a good chapter about airdams, splitters and spoilers
It covers the effect on sedans (production type cars)

As for rear hatch lifting....
It will depend on pressure differential
Perhaps pressure below hatch is normal but pressure above is much lower due to airflow swirling around behind the MR2 rear window.
I used to think that the orange and green tictacs gave you special powers. The orange ones would make you stronger and the green ones would make you faster. So i used to eat some green ones and run around my lounge as fast as i could, then eat the orange ones and try to pick up the sofa. I wish it were true!
User avatar
KinLoud
** Moderator **
 
Posts: 2893
Joined: Thu May 16, 2002 7:39 pm
Location: Auckland


Return to Tech Questions

Who is online

Users browsing this forum: Google [Bot] and 26 guests