Hmmm... Might this work on the back of a car..?

[Logic]

https://www.youtube.com/watch?v=dLlJRujBWos

I'm thinking this might make for 'shorter tails' (but still how effective?) behind cars.
ie: tails at angles that are normally 'stalled' causing turbulent air.
And are at a shorter, more manageable length.

I like the 'fully automated', zero actuation energy, of them.
I 'd want to try spring loading them a little. (adjustable) They stay 'fully automated', but you have a 'trim tab' so to speak. Like the birds do..? I think so?

Lift to opposed sides cancels... so that looks like a smaller wake to me..?
Those springed 'trim tabs' should give you 'rudder control'...
Which has a torque component down the 'centre' of the vehicle.. That's 'lean'. in the wrong direction if you're thinking aircraft controls. (and 2 wheelers)
Inverting the 'rudder'? That tries to straighten you when you want to turn, but will ameliorate tail-happiness at speed.
Rudder in front of rear tire contact patch?

Hmmm... More lift... Is there a forward/backward component to that force, 'pushing/sucking' on the wing?
He said: "...pressure damp... prevents high pressure...from..." behind the wing, moving forward..!
Those look like small 'sails' to me..?

Interesting non the less

[aerohead]

Each feather on a bird is attached at feather follicles, which contain nerve endings, leading to the brain.
As a bird 'fledges', it's brain 'learns' how to morph its wings and tail, to accomplish it's flight dynamics ( like learning to crawl, walk, and run ).
--------------------------------------------------------------------------------------
Birds are 'most aerodynamic ' ( lowest drag ) during 'bounding flight', or' 'stooping,' where the feet and feathers are held as close as can be to the body, which then takes on the form of a 'streamline body of revolution'. A 'bomb'. Perrigrine Falcon at 244-mph ( 392-km/h ).
--------------------------------------------------------------------------------------
Automobiles would experience no benefit with the inclusion of 'feathers.' And their danger to cyclists and pedestrians would never allow them to make it through the certification process.
--------------------------------------------------------------------------------------
Aft-body length requirements for lowest drag are rooted in the adverse pressure gradient / flow separation relationship. No cheating possible.

[Logic]

No one?
That's a video to save you reading:

Distributed feather-inspired flow control mitigates stall and
expands flight envelope
https://www.bamlab.princeton.edu/_fi...fd70b218cf.pdf

The paper does have lots of pictures based on self actuating spanwise flaps on aircraft wings. (Tested)
(Can people still read and comprehend..?
Do people consider research worth reading?
Would they consider it worth reading if it was posted by someone else..?? )

[kach22i]

Originally Posted by Logic

Hmmm... Might this work on the back of a car..?

In the video they stated similar stall benefits no matter the position, even on aft locations of the wing.

The simplified model flaps that were of a clear material looked to be rapidly ripping away in a turbulent dance. I have been told this was bad, at least as it applied to the tonneau cover on my pickup truck.

I know what happens to flags over time, the ends fray, and same thing happens to the bottom of hovercraft skirts. On hovercraft the frantic pressure gradients may create an acoustic signature heard by fish - at least that's my theory based on an event I experienced plus some reading done years later.

I recently went to a funeral ceremony at the Great lakes National Cemetery for a departed Vietnam veteran friend. For a moment I thought I had a flat tire until I realized the sound was from all the American flags on a windy day.

Sound is energy, and this probably means an inefficient waste of some kind depending on the example (flag, hovercraft skirt, flexible wing flap....).

I did a quick search for "flexible wickerbill aerodynamics" thinking somebody has looked into this, but found nothing related to this thread's twist on the topic.

In short: I think you are flapping in the wind.

EDIT:

I'm starting to read the PDF, and regarding the oscillations creating vortexes this topic does indeed seem to be related to the Gurney Flap Spoiler or so-called Wickerbill.

So I'll just warn ya, Aerohead is all about "attachment", and probably regards vortex creation as wasted energy (in general).

I'm less set in my ways and say give it a try, the Cybertruck managed to get vortexes to work in their favor, right?

https://damogranlabs.com/2019/12/tes...-aerodynamics/

[Piwoslaw]

Slightly related: I once tossed up the idea of a "gently morphing" boattail, parts of which could up/down or left/right a bit, allowing the tail to keep its general shape but better fit into the changing wake, depending on speed, sidewinds, and local turbulences.

It would be stiff (as opposed to using soft or elastic elements), with sensors in key locations feeding data by which servomotors would slightly move their relevant pieces.

[Logic]

Originally Posted by Piwoslaw

Slightly related: I once tossed up the idea of a "gently morphing" boattail, parts of which could up/down or left/right a bit, allowing the tail to keep its general shape but better fit into the changing wake, depending on speed, sidewinds, and local turbulences.

It would be stiff (as opposed to using soft or elastic elements), with sensors in key locations feeding data by which servomotors would slightly move their relevant pieces.

I have been thinking along the same lines.
Somewhere between stiff and flexible there must a flexible enough to bend but not flap in the wind. Probably with dampers in the mix.
Thing is it would take a lot of expensive time and money building and testing such.

These guys have already done the equivalent of a short, more manageable boat tail with 'flappy bits' study.
I do hope they also do a slightly sprung 'flappy bits' study.

[Logic]

Originally Posted by kach22i

In the video they stated similar stall benefits no matter the position, even on aft locations of the wing.

The simplified model flaps that were of a clear material looked to be rapidly ripping away in a turbulent dance. I have been told this was bad, at least as it applied to the tonneau cover on my pickup truck.

I know what happens to flags over time, the ends fray, and same thing happens to the bottom of hovercraft skirts. On hovercraft the frantic pressure gradients may create an acoustic signature heard by fish - at least that's my theory based on an event I experienced plus some reading done years later.

I recently went to a funeral ceremony at the Great lakes National Cemetery for a departed Vietnam veteran friend. For a moment I thought I had a flat tire until I realized the sound was from all the American flags on a windy day.

Sound is energy, and this probably means an inefficient waste of some kind depending on the example (flag, hovercraft skirt, flexible wing flap....).

I did a quick search for "flexible wickerbill aerodynamics" thinking somebody has looked into this, but found nothing related to this thread's twist on the topic.

In short: I think you are flapping in the wind.

EDIT:

I'm starting to read the PDF, and regarding the oscillations creating vortexes this topic does indeed seem to be related to the Gurney Flap Spoiler or so-called Wickerbill.

So I'll just warn ya, Aerohead is all about "attachment", and probably regards vortex creation as wasted energy (in general).

I'm less set in my ways and say give it a try, the Cybertruck managed to get vortexes to work in their favor, right?

https://damogranlabs.com/2019/12/tes...-aerodynamics/

Ye the turbulence on a trailing edge does seem to 'roll by' in waves and I don't care for all that mad flapping either.

I wonder what might have happened had they not hinged the flaps but made them thin out with length as feathers do.
ie: More and more flexible as you move from the root to the tip of the 'flaps'

I do agree that attached flow on a long 'low angle' tail is best aerodynamically.
But it's impractical and does have that most undesirable weather-cocking effect on vehicles that might be avoided with, a more mature variation of, this idea.


I like Dielectric Barrier Discharge (DBD) as a means of keeping flow attached to a short tail too:
https://ecomodder.com/forum/showthre...n-41356-3.html
"... the measured drag reduced by over 14% at 26.8 m/s (60 mph) and over 10% at 31.3 m/s (70 mph)..."

https://www.youtube.com/watch?v=-v67vVTGgIs

IMHO you gain more from the drag reduction of DBD than you lose in powering the DBD..?
It's also as easy as some Kapton Tape and strips of Tin Foil!
(and those low amp but 20kV PSUs on Amazone etc)

It would also look cool as hell!
And provide endless: "What's this? OUCH!" entertainment!

https://www.nature.com/articles/s41598-019-42284-w


But you can't beat the 'zero input energy' these 'feather flaps' provide.

[aerohead]

Originally Posted by Logic

No one?
That's a video to save you reading:

Distributed feather-inspired flow control mitigates stall and
expands flight envelope
https://www.bamlab.princeton.edu/_fi...fd70b218cf.pdf

The paper does have lots of pictures based on self actuating spanwise flaps on aircraft wings. (Tested)
(Can people still read and comprehend..?
Do people consider research worth reading?
Would they consider it worth reading if it was posted by someone else..?? )

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
------------------------------------------------------------------------------------
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.

[Logic]

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
------------------------------------------------------------------------------------
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.

"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!

[freebeard]

I like the cold plasma actuators. They could have over-the-air updates where feathers can't. Today, it's mainly because I'm listening to Malcolm Bendall and Jordan Collin (Alchemical Science) on Plasmoids from Space.

Malcolm Bendall and Jordan Collin - Thunderstorm Generator Update