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

Reply  Post New Thread
Submit Tools LinkBack Thread Tools
Old 08-28-2012, 02:22 PM   #71 (permalink)
Master EcoModder
christofoo's Avatar
Join Date: Mar 2012
Location: Salt Lake City
Posts: 292

00C - '00 Toyota Corolla
90 day: 43.54 mpg (US)
Thanks: 147
Thanked 188 Times in 72 Posts
Originally Posted by ChazInMT View Post
Anyway, when looking at louvers through the lens of this idea, it is less then optimum. As always, I have to say that filling the wake will always yield a better result than nothing. But at the end of the day, we want the air to return it's potential energy to the car and in my mind, the air cascading down the louvers does not have the angled surface to push against.

So the louvered Kamm will help by eliminating the potential for large vortices to form at the back of the car, but it does not allow the air to push on the car.
Maybe louvers don't break your idea. So long as there is dead air between the louvers (need to ensure it's sufficiently closed along the azimuth so air doesn't slip in through the sides), the pressure in the dead zone will be equal to the pressure applied by the descending stream. - Just because it isn't a solid surface doesn't mean you can't push on it - The right question to ask is whether there is a substantial difference in the flow characteristics around a solid smooth surface vs a discreet chopped louver-tip surface. I expect the answer to be that the solutions approach each other as the louver spacing is reduced. How small? I almost called it the boundary layer thickness, but I think I'm grasping for a term I can't name - more like the "characteristic detachment length", which must be somewhere between 0.5" and 6".

Anyway, there's one way to find out. Build a louvered rear-window cover and perform A-B-C-A testing, with plastic wrap over the louvers for C.

I agree that louvers are unlikely to be aerodynamically as good as a smooth surface (in addition to being more challenging to design and fab). I'm disputing whether it's likely to be aerodynamically "almost as good" or "not nearly as good". If I'm correct that it's "almost as good" (which we can talk forever about until ABCA ), then I think the other benefits I listed are worth considering. MPG can't be the only figure of merit. The M is the value we get out of that equation, but I also get value out of comfort and convenience.

(Sorry for the threadjacking.)

Last edited by christofoo; 08-28-2012 at 02:35 PM..
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

Old 09-02-2012, 04:40 PM   #72 (permalink)
Master EcoModder
2000neon's Avatar
Join Date: Feb 2012
Location: Ontario, Canada
Posts: 596

VX - '94 Honda Civic VX
Team Honda
90 day: 47.95 mpg (US)
Thanks: 133
Thanked 89 Times in 66 Posts
Update: As I said earlier, I was wondering about this for not if I build it, but WHEN I build it. So on that note, I have a pretty cool update that I will be posting tonight after work in my other thread. Found here:

All build details and pictures will be posted there.

  Reply With Quote
Reply  Post New Thread

Thread Tools

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com