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Old 01-01-2013, 01:11 PM   #27 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
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Happy new year to you too. And thanks for posting all these videos - very instructive!

Re the non-fluttering tufts on the Prius glass and the "dead air" hypothesis...

Quote:
Yes, that is what initial results appear to show.
I still think what we're looking at is the well-designed Prius shape, leading to "clean" flow with little turbulence right to the end of the car (on the top, anyway). I'd bet a dollar if there were some way to "release" those tufts from the glass at speed, they'd be instantly swept off.

How could this be tested? One of our members recently drove his boat-tailed Ford Probe hatchback after it got covered by a dump of snow and found some interesting patterns (note: car has a steeper hatch angle and more pronouced roof/hatch transition):

Before:



After a 100 mph run:



From: http://ecomodder.com/forum/showthrea...tml#post346077

Lucky for you, that particular test approach isn't an option! It's food for thought though.

The Civic rear glass shows what we'd expect to see: the boundary layer getting progressively more turbulent (presumably thicker) as flow descends the glass, with separation imminent at the base (but not established as a sustained trapped separation "bubble" as we saw at the base of the steeper glass on the Corolla). Some of the Civic's bottom window tufts flick back ~90 degrees occasionally indicating some reverse flow.

One last thought: testing for vortex formation off the C-pillar, you might try attaching much longer tufts. If placed in the right spot, they'd have a better chance of being lifted clear off the vehicle and drawn away by the vortex.
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