Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 05-04-2015, 01:27 PM   #21 (permalink)
EcoModding Apprentice
 
Join Date: Feb 2010
Location: Howells Ne
Posts: 126

Supra - '88 Toyota Supra

superhawk - '98 Honda superhawk
Last 3: 27.62 mpg (US)

Lesabre - '96 buick lesabre
3800
90 day: 25.85 mpg (US)

Saturn - '97 Saturn Sc2
Team Saturn
Sports Cars
90 day: 39.12 mpg (US)

Truk - '99 Ford F150
Team Ford
Pickups
90 day: 24.43 mpg (US)

Golf - '03 Vw Golf
90 day: 38.57 mpg (US)
Thanks: 17
Thanked 7 Times in 6 Posts
Looks like a neat and cheap project. Did you notice a gain in fuel economy and or more stability going down the road?

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 05-05-2015, 05:49 PM   #22 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
intended function

Quote:
Originally Posted by NeilBlanchard View Post
Hi folks,

Can I ask what is the intended aerodynamic function of these side skirts?

Personally, it feels a bit counterintuitive -- I would think that you want to have air "escape" out from under the car; and not to trap it under the car. And none of the ultra-low Cd cars that I am aware of have anything like this.
They're borrowed from racing where they segregate the flow between sides and bottom (as pickups are using step rails today),making a 'flush' pathway for the air across the tires.Sometimes,air fence flow straighteners are added to keep the air moving longitudinally,not transversly).
The John Shinella' Trans Am Firebird units were shown in the Lockheed tunnel to cut drag.
Lower skirts have been used in ground-effects cars,but I don't think there's a drag advantage.
IMHO I would not have them lower than the belly.I used them on the CRX
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
BamZipPow (05-06-2015)
Old 05-06-2015, 03:24 AM   #23 (permalink)
EcoModding Apprentice
 
Join Date: Apr 2015
Location: USA
Posts: 148

VanDelay - '89 Ford Econoline E-150 XL
90 day: 15.93 mpg (US)

Old White Civic - '98 Honda Civic LX, AT
90 day: 33.18 mpg (US)
Thanks: 5
Thanked 50 Times in 43 Posts
Quote:
Originally Posted by aerohead View Post
...Sometimes,air fence flow straighteners are added to keep the air moving longitudinally,not transversly)....
I'm listening
  Reply With Quote
The Following User Says Thank You to mwilliamshs For This Useful Post:
aerohead (05-06-2015)
Old 05-06-2015, 05:59 PM   #24 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
straighteners

Quote:
Originally Posted by mwilliamshs View Post
I'm listening
The 1987 Olds AEROTECH would be an example
http://deansgarage.com/wp-content/ga...n_at_speed.jpg
A bunch of Pontiacs had these as styling features.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following 2 Users Say Thank You to aerohead For This Useful Post:
BamZipPow (05-06-2015), Tango Charlie (01-11-2016)
Old 05-06-2015, 07:34 PM   #25 (permalink)
EcoModding Apprentice
 
Join Date: Feb 2010
Location: Howells Ne
Posts: 126

Supra - '88 Toyota Supra

superhawk - '98 Honda superhawk
Last 3: 27.62 mpg (US)

Lesabre - '96 buick lesabre
3800
90 day: 25.85 mpg (US)

Saturn - '97 Saturn Sc2
Team Saturn
Sports Cars
90 day: 39.12 mpg (US)

Truk - '99 Ford F150
Team Ford
Pickups
90 day: 24.43 mpg (US)

Golf - '03 Vw Golf
90 day: 38.57 mpg (US)
Thanks: 17
Thanked 7 Times in 6 Posts
I want one
  Reply With Quote
Old 05-06-2015, 08:32 PM   #26 (permalink)
EcoModding Apprentice
 
Join Date: Apr 2015
Location: USA
Posts: 148

VanDelay - '89 Ford Econoline E-150 XL
90 day: 15.93 mpg (US)

Old White Civic - '98 Honda Civic LX, AT
90 day: 33.18 mpg (US)
Thanks: 5
Thanked 50 Times in 43 Posts
are the straighteners the horizontal surfaces (and the transition to such) at the rear of the skirts?
  Reply With Quote
Old 05-07-2015, 05:16 PM   #27 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
are the

Quote:
Originally Posted by mwilliamshs View Post
are the straighteners the horizontal surfaces (and the transition to such) at the rear of the skirts?
Yes.They intrude into the airstream and create a physical boundary which directs the flow and helps isolate it from hostile pressure gradient across the 'border' which might otherwise induce a span-wise flow,spinning up into power-robbing vortices.
Once the flow is aligned with the fence,it builds momentum which tends to keep it moving in that direction.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 05-07-2015, 06:16 PM   #28 (permalink)
EcoModding Apprentice
 
Join Date: Apr 2015
Location: USA
Posts: 148

VanDelay - '89 Ford Econoline E-150 XL
90 day: 15.93 mpg (US)

Old White Civic - '98 Honda Civic LX, AT
90 day: 33.18 mpg (US)
Thanks: 5
Thanked 50 Times in 43 Posts
i got most of that...

the horizontal fins on the side skirts...

Quote:
Originally Posted by aerohead View Post
...They intrude into the airstream

They stick out from the car

and create a physical boundary

and air can't go through them

which directs the flow

so the air gets pushed by the fin

and helps isolate it

and this keeps it separated


from hostile pressure gradient across the 'border' which might otherwise induce a span-wise flow,spinning up into power-robbing vortices.

from...????

Once the flow is aligned with the fence,

once the air gets pushed by the fence

it builds momentum which tends to keep it moving in that direction.

it keeps going that way
is that about right?

Last edited by mwilliamshs; 05-07-2015 at 06:22 PM..
  Reply With Quote
The Following User Says Thank You to mwilliamshs For This Useful Post:
aerohead (05-07-2015)
Old 05-07-2015, 06:36 PM   #29 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
spanwise flow

Quote:
Originally Posted by mwilliamshs View Post
the horizontal fins on the side skirts...
Yep,you've got a good handle on it.
For the spanwise flow,here's a better explanation:

If the pressure below the car was higher than the pressure besides the car,the high pressure air would bleed up into the lower pressure air alongside the car,moving transversly,or,sideways (spanwise if on a wing).
This transverse flow spins up into vortices,as a fast-moving tributary meeting a slow-moving river,or as the jet stream spins warm,rising,moist gulf air over Colorado into supercell tornadoes.
The vortices lockup kinetic energy which can never be converted to pressure,ultimately raising the pressure drag.
If the fence can keep the two pressure regimes apart,we can skip the vorticity.
Winglets on commercial airliner wingtips are a form of exaggerated fence which helps spanwise vorticity from forming.

__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/

Last edited by aerohead; 05-07-2015 at 06:39 PM.. Reason: add to
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
BamZipPow (05-07-2015)
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Effectiveness of side skirts? fanamingo Aerodynamics 14 04-07-2022 01:57 PM
Temporary side skirts? atomicradish Aerodynamics 9 07-02-2011 06:52 PM
Finally Got Side Skirts Big Dave Aerodynamics 16 07-01-2009 10:03 PM
Side skirts? hamorhead Aerodynamics 6 09-16-2008 06:52 PM
Side skirts fastening tasdrouille Aerodynamics 9 08-01-2008 01:24 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com