Do Overlapping Feathers on Swifts Offer Insights for Aircraft Design?

[Aeronautic Freek]

Do you thing swift birds(most aerodynamics birds; 10months in the air without landing,fastest birds in horizontal flapping flight -169km/h) have some benefits of overlaping feathers which gives rough surface?
Can planes benefits from this?https://www.researchgate.net/publication/263394314_Gliding_Swifts_Attain_Laminar_Flow_over_Rough_Wings

 

[boneh3ad]

It's unclear what you are trying to ask here. As far as I know, most birds have feathers that overlap.

 

[Aeronautic Freek]

It's unclear what you are trying to ask here. As far as I know, most birds have feathers that overlap.

overlap feathers are far more ticker than air boundery layer ,isnt it?
isnt that cause huge skin friction drag?

if we compare to airplane,birds wings are very very rough..

 

[tech99]

Rough surfaces are sometimes used to reduce drag. For instance, a golf ball. The roughness re-energises the boundary layer and delays separation. But it is difficult to do.

 

[Aeronautic Freek]

Rough surfaces are sometimes used to reduce drag. For instance, a golf ball. The roughness re-energises the boundary layer and delays separation. But it is difficult to do.

so you think birds use this "trick" to delay flow separation?

 

[boneh3ad]

overlap feathers are far more ticker than air boundery layer ,isnt it?
isnt that cause huge skin friction drag?

if we compare to airplane,birds wings are very very rough..

You seemingly compared the roughness due to overlapping feathers on a swift to other birds. This isn't, as far as I know, an uncommon feature among birds. I'd expect that the shape of the wings, the fact that they can rotate them like a hummingbird, and the nature of the skeleton underneath are all larger factors.

Rough surfaces are sometimes used to reduce drag. For instance, a golf ball. The roughness re-energises the boundary layer and delays separation. But it is difficult to do.

so you think birds use this "trick" to delay flow separation?

Roughness on a golf ball works by inducing transition to turbulence. When that happens, the boundary layer is more resistant to separation and therefore the golf ball has a smaller wake and less drag. Notably, the golf ball has substantially more viscous drag, but the reduction in form drag is even larger, so it is a net reduction in drag.

Bird's wings do not feature large separated regions. They are thin, sleek, and the boundary-layer would generally remain attached when soaring/cruising. In that sense, intentionally tripping the boundary layer would only increase skin friction drag and would not do anything to reduce form drag. There are almost certainly other effects due to roughness on the wings, but any positive effect would not be analogous to a golf ball.

 

[Aeronautic Freek]

Bird's wings do not feature large separated regions. They are thin, sleek, and the boundary-layer would generally remain attached when soaring/cruising. In that sense, intentionally tripping the boundary layer would only increase skin friction drag and would not do anything to reduce form drag. There are almost certainly other effects due to roughness on the wings, but any positive effect would not be analogous to a golf ball.

so that mean that overlaping fathers cause drag to the birds wing,so birds don't have any benfits from this,so mother nature/or evolution(if it exist) didnt make "good job"?

 

[boneh3ad]

so that mean that overlaping fathers cause drag to the birds wing,so birds don't have any benfits from this,so mother nature/or evolution(if it exist) didnt make "good job"?

Who said that? There are a lot more factors that go into what makes an effective bird design than just drag. Even then, it's possible that the ridges from overlapping feathers have other positive aerodynamic effects that are less obvious. All I said is that they do not function like golf ball dimples.

 

[Aeronautic Freek]

Who said that? There are a lot more factors that go into what makes an effective bird design than just drag. Even then, it's possible that the ridges from overlapping feathers have other positive aerodynamic effects that are less obvious. All I said is that they do not function like golf ball dimples.

but do you know what is poistive aerodynamics effects from this?

 

[boneh3ad]

but do you know what is poistive aerodynamics effects from this?

There doesn't need to be a positive aerodynamic effect from this. It likely provided some kind of evolutionary advantage sometime in the swift's evolutionary history, but that advantage need not be aerodynamic.

 

[tech99]

https://www.quora.com/What-are-the-little-tabs-near-the-leading-edge-of-an-airplanes-wing
This tab describes the use of leading edge tabs on an aeroplane wing to improve lift and lower stalling speed at the expense of drag. Maybe birds use the rougness to improve slow speed flight and stall characteristic.

 

[Baluncore]

but do you know what is poistive aerodynamics effects from this?

The primary reason for having feathers is thermal insulation while being exposed to airflow.

Feathers also shed water, self repair by zipping back into place after a disturbance, and can grow topologically from a pore in the skin. The fact that birds can fly would be irrelevant if they did not live long enough to first fledge, and then as adults, keep eggs warm in their nest.

 

[DaveE]

You seem to imply that since Swifts are good at flying, then evolution has made a perfect solution to the flying problem. That's not really how natural selection works, things are optimized for overall performance (reproduction, really) as much as time and evolution allows. Perfection is actually quite rare, since as the creature's performance gets better the selection pressure to continue to improve is reduced. Evolution is also usually incomplete, as creatures are always adjusting to different types of selection pressure. Darwin's Finches, for example, never settled on the "best" beak design; it changed based on their environment.

It's not aeronautical, but if you want to learn more about evolution, I highly recommend "The Selfish Gene" by Richard Dawkins.

 

[shjacks45]

Do you thing swift birds(most aerodynamics birds; 10months in the air without landing,fastest birds in horizontal flapping flight -169km/h) have some benefits of overlaping feathers which gives rough surface?
Can planes benefits from this?https://www.researchgate.net/publication/263394314_Gliding_Swifts_Attain_Laminar_Flow_over_Rough_Wings

View attachment 265959

There are soaring birds, they've been extensively studied by aircraft designers. However rarely do you see Swifts soaring, rather they use their wings for propulsion, and rapid changes of direction, therefore a powered wing that changes in shape and attitude many times per second. Physically, you can't cover an area with randomly shaped objects (like scales or feathers) without some overlap. Only Raptors have non-overlapped pin feathers that act as ailerons/spoilers to control soaring. There are farm fields with Swift picking off insects. Note that after a few wing flaps, the Swift folds up the wings & makes like a bullet (maybe body lift?). Apparently the drag of the wings on velocity deters gliding.