Quote:
Originally Posted by aerohead
I read the paper.
I noticed some 'conditions', 'caveats', 'context':
1) The interest is for 'unmanned aerial vehicles':
A) operating at flight conditions
B) above Earth's boundary-layer
C) in two-dimensional flow
D) with Reynolds number dependency
E) of a perfectly-streamlined wing section
F) of varying angle of attack
G) with particular interest in high-angle-of-attack 'stalled' flow
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None of this would have anything to do with road vehicle aerodynamics, other than introducing a 'flap' ( rear spoiler ) capable of reaching up through separated flow high enough to reach the reversal point, at which flow reattached, a greater negative pressure regime would exist, such that pressure recovery might continue within the 'mended' flow, raising base pressure, reducing pressure drag, reducing overall drag.
1967 technology.
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"The interest" is for science, to see what would happen. To learn new things and be able to update our outdated view with that learned new knowledge...
That is what drives progress.
What happened is that at the angle of attack at which a wing is stalled (turbulent, unattached flow) there was 39% less drag.
There is no reason to believe that if a boat tail is short (and thus more practical) a similar type of turbulent, unattached flow would not be evident.
Therefore:
A similar type of flap/s might have a similar effect.
That's called deduction. It is the means by which experiments like this are refined and uses found for newly gained knowledge.
What are the big difference between the conditions above the wing's trailing edge of that model plane and the conditions above and on the sides of a short boat tail on a car?
Is the airspeed and thus Renaults # different to any large degree?
Yes; air gets compressed under wings (ground effect) and air under a car is influenced to stay more put, with one plane less to get out of the way to, but 3 sides out of 4 isn't bad.
2 dimensional flow yes. So is that the mountainous mole-hill atop which all and sundry should dismiss an interesting new finding and a question involving the kind of turbulent, unattached flow and drag one would also find on a short boat tail..?
I also NB that the flaps would be on the back thinning boat-tail of a car and have a tendency to lie flat against the tail at around zero airspeed.
That would mean that for any pedestrian to hurt themselves, they would have to sprint into the back of your car while it's moving at a considerable speed for a ambulatory human.
I'd be happy to help you test that. I'll drive the experimental vehicle and you can run after me trying to injure yourself on the flaps!
I don't envy you with nothing new under your sun to to wonder at.
But think we are all... most fortunate! the wheel was invented before your birth!
