A sweltering day in India brought out the local giant fruit bats (also called Indian flying foxes) to keep cool in the river. Normally nocturnal, they made a rare daytime appearance to beat the heat. Wildlife photographer Hardik Shelat was lucky enough to catch these awesome images of the bats in flight. True to their name, the animals have wingspans ranging from 1.2 to 1.5 meters, which should give them some impressive lift, even when gliding down near the water. (Image credit: H. Shelat; via Colossal)
Tag: gliding
Skydiving Salamanders
The wandering salamander can spend its entire 20-year lifespan in the canopy of a coast redwood. When predators come calling, they have a special skill that helps them get away: skydiving. These little amphibians have no webbed appendages and no wings, but they’re some of the most skillful skydivers out there. By carefully repositioning its tail and feet, a wandering salamander controls its pitch, yaw, and roll. It’s not only able to orient itself as it falls; it can actually steer itself to a safe landing! Other salamander species, as seen in the video above, do not share this skill. Check out the full Deep Look video to see these incredible gliders in action. (Video and image credit: Deep Look; see also C. Brown)
Millennium Falcon’s Glide
In what seems to be a tradition now, a group at MIT imagined how the Millennium Falcon would perform if it lost its engines during atmospheric flight. Their hypothetical scenario took place in the Battle of Endor, with the Falcon flying at an altitude of 2 kilometers.* Could Han Solo and Chewbecca safely glide the craft down?
Using computational fluid dynamics, the group found the Millennium Falcon has a glide ratio of only 1.8, meaning it travels forward 1.8 kilometers in the time it takes to lose one kilometer of altitude. Its namesake bird, on the other hand, has a glide ratio of 10. The Corellian freighter might not be the best glider out there, but the team estimated that it could safely manage its 3.6 kilometer glide down. (Image credit: S. Costa et al.; see also X-Wing Re-entry and AT-AT Flow)
*I’m definitely overthinking this, but now I’m really wondering what atmospheric characteristics they used for Endor. And what’s Endor’s gravity like?
Beijing 2022: Ski Jumping
In ski jumping, aerodynamics are paramount. Each jump consists of four segments: the in-run, take-off, flight, and landing. Of these, aerodynamics dominates in the in-run — where jumpers streamline themselves to minimize drag and maximize their take-off speed — and in flight. During flight, ski jumpers spread their skis in a V-shape and lift their arms to the sides to turn themselves into a glider. Their goal is to maximize their lift-to-drag ratio, so that the air keeps them aloft as long as possible. Because of the short flight time and high risk of taking jump after jump, many elite ski jumpers use wind tunnel time to practice and hone their flight positioning, as seen in the video below.
Weather also plays a significant role in ski jumping; it’s one of the few sports where a headwind is an advantage to athletes. To try to adjust for wind effects, scoring for the sport uses a wind factor. (Image credit: T. Trapani; video credit: NBC News)
Flying on Soap Films?
YouTube channel Viral Video Lab has two videos showing 3D-printed gliders flying on wings formed from soap films. It’s a neat idea for a toy aircraft, though obviously not practical. But are the videos real? The channel features plenty of obviously fake concepts, like perpetual motion machines, and explicitly states in its About page that “videos shown on the channel may contain CGI effects.” They’re clearly not strangers to stretching the truth.
Sadly, I don’t have the means to properly test the concept, but it at least seems plausible (although there are some flight sequences in the videos themselves that I don’t think are totally real). There are bubble solutions out there capable of making quite giant, long-lasting bubbles, though they are more complicated than the simple soap and water solution suggested in the video. And having essentially flat wings doesn’t preclude gliding, as long as you have a positive angle of attack. I’d be interested to see if someone with a 3D-printer can recreate the effect. Let me know if you give it a try! (Video credit: Viral Video Lab; via Gizmodo)
When Squids Fly
Some species of squid fly at speeds comparable to a motorboat for distances of 50 meters. The cephalopods get into the air the same way they swim underwater: by expelling a jet of water through the center of their body. Once aloft, the squids spread their tentacles to form a semi-rigid wing-like surface for lift. They can also use fins on their mantle as a canard for additional lift or control of their altitude. Researchers suspect the squids use flight as an escape mechanism to put distance between themselves and predators, but it could also be a low-energy migration strategy since a single pulse carries a squid farther in air than in water. (Video and image credit: TED-Ed)
The Best of FYFD 2020
2020 was certainly a strange year, and I confess that I mostly want to congratulate all of us for making it through and then look forward to a better, happier, healthier 2021. But for tradition and posterity’s sake, here were your top FYFD posts of 2020:
- Juvenile catfish collectively convect for protection
- Gliding birds get extra lift from their tails
- How well do masks work?
- Droplets dig into hot powder
- Updating undergraduate heat transfer
- Branching light in soap bubbles
- Boiling water using ice water
- Concentric patterns on freezing and thawing ice
- Bouncing off superhydrophobic defects
- To beat surface tension, tadpoles blow bubbles
There’s a good mix of topics here! A little bit of biophysics, some research, some phenomena, and some good, old-fashioned fluid dynamics.
If you enjoy FYFD, please remember that it’s primarily reader-supported. You can help support the site by becoming a patron, making a one-time donation, buying some merch, or simply by sharing on social media. Happy New Year!
(Image credits: catfish – Abyss Dive Center, owl – J. Usherwood et al., masks – It’s Okay to Be Smart, droplet – C. Kalelkar and H. Sai, boundary layer – J. Lienhard, bubble – A. Patsyk et al., boiling – S. Mould, ice – D. Spitzer, defects – The Lutetium Project, tadpoles – K. Schwenk and J. Phillips)
Undulating Keeps Flying Snakes Steady
Flying snakes undulate through the air as they glide. But, unlike on land, these wiggles aren’t for propulsion. A new study shows instead that they are key to the snake staying stable in flight.
Upon take-off, a flying snake flattens its body, forming a wing-like shape that helps them generate lift and control drag. But while they glide, they also slither and pitch their tail.
Researchers recorded more than 150 flights by live snakes, then used that data to construct their own digital snake. The model could fly like a real snake or be tested without undulations to see what would happen. The researchers discovered that, without that mid-air slithering, the snake quickly lost control and rolled to the side. (Image and research credit: I. Yeaton et al.; via NYTimes; submitted by Kam-Yung Soh)
Gliding Birds Get Extra Lift From Their Tails
Gorgeous new research highlights some of the differences between fixed-wing flight and birds. Researchers trained a barn owl, tawny owl, and goshawk to glide through a cloud of helium-filled bubbles illuminated by a light sheet. By tracking bubbles’ movement after the birds’ passage, researchers could reconstruct the wake of these flyers.
As you can see in the animations above and the video below, the birds shed distinctive wingtip vortices similar to those seen behind aircraft. But if you look closely, you’ll see a second set of vortices, shed from the birds’ tails. This is decidedly different from aircraft, which actually generate negative lift with their tails in order to stabilize themselves.
Instead, gliding birds generate extra lift with their maneuverable tails, using them more like a pilot uses wing flaps during approach and landing. Unlike airplanes, though, birds rely on this mechanism for more than avoiding stall. It seems their tails actually help reduce their overall drag! (Image and research credit: J. Usherwood et al.; video credit: Nature News; submitted by Jorn C. and Kam-Yung Soh)
Morphing Wings Using Real Feathers
Although humanity has long been inspired by bird flight, most of our flying machines are nothing like birds. Engineers have struggled to recreate the ease with which birds are able to morph their wings’ characteristics as they change from one shape to another. Now researchers have built a biohybrid robot, PigeonBot, that uses actual pigeon feathers as part of its morphing design.
Many species of birds, including pigeons, have Velcro-like hooks in the microstructure of their feathers. These hooks help the flight feathers stick to one another and create a continuous wing surface that air cannot easily slip through, even as the wing drastically changes shape. By using actual feathers, PigeonBot shares this advantage.
PigeonBot also has a somewhat minimalist design in its articulation, using only a wrist and finger joint in each wing to control shape. The feathers are connected through an elastic ligament, which — along with their microstructure — allows them to smoothly change shape under aerodynamic loads. The end result is a remarkably capable and agile biorobot researchers can use to better understand how birds control their flight. (Image and research credit: L. Matloff et al. and E. Chang et al.; via NPR and Gizmodo)
