Aerodynamics, birds vs us

[SectorOne]

With all the talk about downforce, drag, drag coefficient etc etc on this forum it got me quite interested in the efficiency of birds.

I get that birds move all the time making any measurements near impossible but let´s say you take an eagle´s wing and then compare it to a manmade wing of the same size.
How would they stack up? Is it even remotely possible to compare the two in some way?
Assuming you make the birds wing static i suppose you can probably get some data from that?

Just curious about just how efficient bird-wings really are. Say a Falcon or an Eagle or any other attack-oriented bird.

[hollus]

Assuming you make the birds wing static...

That's a bit ask, and what you get might no longer be "a bird".
Birds, and specially falcons, fold their wings at speed much in the way a supersonic fighter does.
Pigeon in the left, falcon in the right:

Birds get to change the angle of attack of the wing at will, and they do all the time.
Birds have flexible wing materials that increase the wing's projected area when flapping down and reduce it when flapping up.
It is not that birds move all the time, it is that they change shape all the time.
And then, birds glide a bit like planes, but they do gain altitude or speed mostly by flapping, which largely consists of literally pushing air down or behind with the wings themselves.

Anyways, there you go, an "immobile" bird:

And you might find some numbers here:
http://arxiv.org/ftp/arxiv/papers/0804/0804.4752.pdf

[SectorOne]

excellent info, i´ll have a read through that pdf right now, thanks

edit: this was pretty cool, good comparison to manmade wing profiles.

[Andres125sx]

Very interesting thread, even when it´s difficult to analize

I guess it´s too much asking, but I´d love to know how does the profile change with different wing positions. As they fold the wings the profile become longer and it must be flatter and reduce drag

Another important point is their wings are not rigid, so I think before stalling, when the airflow try to detach from the wing, the feathers must fold due to the low pressure area so the profile is actively adapted to the airflow, so it can be a high lift airfoil when low speed, wich becomes a flatter airfoil when speed is increased by itself

[Blanchimont]

From http://en.wikipedia.org/wiki/Lift-to-dr ... o#Examples
http://de.wikipedia.org/wiki/Eta_%28Flugzeug%29
and http://www.allstar.fiu.edu/aero/winggrid1.html

Lift/drag
Albatross 20 to 25
Sailplane up to 60 to 70

The aspect ratio of the wing for the sailplane is of course higher, it would be unpractical for the albatross to have wings with a AR of 50. This site http://www.wfis.uni.lodz.pl/edu/Proposal.htm also seems to be worth a read.

Well done, evolution! =D>

[Shrieker]

Well done, evolution! =D>

Well done evolution ? You surely meant "well done God".









Just trolling.

[strad]

[Sebp]

Well done, evolution! =D>

Well done evolution ? You surely meant "well done God".









Just trolling.

Hahaha, what a fitting discussion to start on Christmas Eve!

All hail the Great Spaghetti Monster!

[SectorOne]

The aspect ratio of the wing for the sailplane is of course higher, it would be unpractical for the albatross to have wings with a AR of 50. This site http://www.wfis.uni.lodz.pl/edu/Proposal.htm also seems to be worth a read.

Well done, evolution! =D>

Talking of wingtips as seen on point 1,1 in the link. This is a pretty interesting solution as well.



Also found an awesome video of a Wandering Albatross on wiki where it starts running to pick up speed then start to generate enough lift to take off.
http://en.wikipedia.org/wiki/Wandering_albatross

[autogyro]

Well done, evolution! =D>

Well done evolution ? You surely meant "well done God".









Just trolling.

OK God, so what about the propeller?

[Blanchimont]

Hmm, not sure if serious. But when was the last time you got your glasses checked, gyro?

Is it true that the Pitot tube should be named Albatross tube instead?
http://people.eku.edu/ritchisong/554notes3.html might suggest it

[autogyro]

I thought God had a problem with bearings and things that rotate.

[hollus]

And He sayeth: rotiting things? No problem! He just does things differently:

[SectorOne]

Watching David Attenborough´s latest show called Conquest of the Skies where he goes through the history of flying animals, well worth a watch if you get to see it, some stunning images as usual.

[Moose]

This thread needs to be renamed "what is the air speed velocity of an unladen swallow"