Thread: Drag penalty for having a shallow rear window angle, and using spoiler to re-attach ?
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Old 10-15-2021, 11:03 AM   #34 (permalink)
aerohead
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' Re: your second picture'
Quote:
Originally Posted by Vman455 View Post
Re: your second picture--

Pressure always acts normal to a surface. The arrows in the lower image are not correct.

A spoiler affects flow upstream because pressure is transmitted through air (fluid) at ~340 m/s. Fitting a spoiler may increase pressure as far upstream as the roof, as I found on my Prius with a small lip spoiler:


Gauge pressures with no lip spoiler


Gauge pressures with lip spoiler


Difference


Lip spoiler for reference

Les than $100 worth of equipment and a couple hours and you can measure yourself and find out what a spoiler does on your car.
Sorry, I couldn't figure out which picture you're referring to. None of my images have 'arrows.'
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