View Single Post
Old 03-17-2008, 03:14 AM   #1 (permalink)
LostCause
Liberti
 
LostCause's Avatar
 
Join Date: Feb 2008
Location: California
Posts: 504

Thunderbird - '96 Ford Thunderbird
90 day: 27.75 mpg (US)
Thanks: 0
Thanked 7 Times in 7 Posts
Strange OEM Aerodynamic Shape (longitudinal roof indents)

While reading the square shapes for aerodynamics thread, I noticed the Opel G90 (cD 0.22) had a weird indent on the top of its roof. At first I thought nothing of it, as it could easily just be a stylistic feature...

G90 Roof Channel


However, while looking around the internet, I came across the Daihatsu UFE (cD 0.26). I noticed it also has the same hatchback shape as the G90 and uses a similar roof channel...

UFE Roof Channel


I can only imagine the feature for three reasons: Style, Stiffness, Aerodynamics. If the first two are discounted, then I imagine they help aerodynamically by shedding vortices just as a NACA duct does.

If you excuse the poor PAINT graphic, you'll see why NACA ducts operate so efficiently. Air sheds over the sharp sides into the trough by forming vortices. I wonder if the OEM roof channels are acting as mild vortex generators?

Vortex Shedding


Maybe I'm just looking a little too deep for something that's not there. It might be something hatchback owners should look into, though. Thoughts?

- LostCause

  Reply With Quote