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Search results for: “lift”

  • Programmable Capillary Action

    Programmable Capillary Action

    Capillary action combines the cohesive forces within a liquid and the adhesive forces between a liquid and solid to enable a liquid to fill narrow spaces, even against the force of gravity. To control capillary action, researchers are 3D-printing what they call “unit cells,” tiny structures that water and other liquids can climb. There’s no pump raising the liquid through these structures, just capillary action.

    In a particularly neat demonstration of the technology, the researchers built a tree-like structure out of many open-walled unit cells and placed the “root” system in a closed reservoir. Capillary action drew liquid up the structure to the tips of its branches, where the dyed water evaporated. The process is similar to transpiration in trees, though in trees, capillary action provides much less of the lift. (Image and research credit: N. Dudukovic et al.; via Nature; submitted by Kam-Yung Soh)

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    Tokyo 2020: Sailing Faster Than The Wind

    It’s a bit mindboggling, but by exploiting physics and geometry, a sailboat can reach speeds faster than the wind propelling it. Steve Mould demonstrates how in this video using some cool tabletop set-ups. Like a wing, a sail generates force by changing the direction of the incoming air. But the optimal speed for a sail is the one where the the flow doesn’t get deflected from its initial path at all (middle). If the sail were moving slower than this, the air would get pushed aside, creating a force that accelerates the boat. If the sail were moving faster, the air’s deflection would generate low pressure that would slow the boat down. Given this ideal match, it’s straightforward to show that, with the right sail angle, a boat can cover more distance than the air pushing it does in the same amount of time (right). Part of the mark of a great sailor is knowing how to manipulate this relationship to maximize your boat’s speed! (Image and video credit: S. Mould)

    Missed some of our earlier Olympics coverage? Check out how to optimize oar lengths for rowing, volleyball aerodynamics, and the ideas behind future swim technologies.

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    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)

  • Skipping Stone Physics

    Skipping Stone Physics

    Skipping stones across water has fascinated humans for millennia, but incredibly, we’re still uncovering the physics of this game today. A recent paper built and experimentally validated a mathematical model of a spinning, skipping disk. The authors found that, in order to skip, a stone needs to generate upward acceleration greater than 3.8 times gravity.

    To get that lift, the stone needs both the Magnus effect and the gyro effect. The Magnus effect is an aerodynamic force generated by an object spinning in a fluid that curves it away from its direction of travel — it’s what curves a corner kick into the goal in a soccer match. The gyro — or gyroscopic — effect also has to do with spinning, but it’s a result of conservation of angular momentum. Essentially, when you try to shift the axis that a rotating object spins around, there’s a force that resists that change. (The classic demo for this uses a spinning bicycle wheel.)

    In stone skipping, the gyro effect helps stabilize the stone’s bounce and, if it’s spinning fast enough, keeps its direction of travel straight. Once the stone’s spinning slows, the Magnus effect can start to curve its trajectory. (Image credit: B. Davies; research credit: J. Tang et al.; via Physics World; submitted by Kam-Yung Soh)

  • Inside Hydroplaning

    Inside Hydroplaning

    When a tire spins over a wet roadway, pressure at the front of the tire generates a lifting force; if that lift exceeds the weight of the car, it will start hydroplaning. To prevent this, the grooves of a tire’s tread are designed to redirect the water. Now researchers have visualized flow inside these grooves for the first time, using a version of particle image velocimetry (PIV). PIV techniques use fluorescent particles to track the flow.

    The results reveal a complicated, two-phase flow inside the tire grooves. As seen in the images above, bubble columns form inside the tire grooves. The team’s results suggest that the bubble columns depended on groove width, spacing, and intersections with other grooves. They also saw evidence of vortices inside some grooves. (Image credit: tires – S. Warid, others – D. Cabut et al.; research credit: D. Cabut et al.; via Physics World; submitted by Kam-Yung Soh)

  • The Fluidity of Worm Blobs

    The Fluidity of Worm Blobs

    The aquatic blackworm forms blobs composed of thousands of individual worms for protection against evaporation, light, and heat. The worms braid themselves together (Image 1). Once a blob forms, it is extremely viscoelastic, displaying properties both solid and fluid in nature (Image 2).

    The worm blobs act like a collective; they bunch up to prevent evaporation that would desiccate the worms. Under intense light, the blob contracts (Image 3). The worms also prefer colder temperatures (again, to prevent evaporation) and will move toward the colder side of a temperature gradient. Under dim light, they’ll move individually, but in brighter light, the worms move collectively as a blob (Image 4).

    To do so, worms on the colder side of the blob pull toward the cold, whereas worms elsewhere in the blob wiggle (Image 5). Their wiggling helps lift the blob and reduce its friction so that the pulling worms can move the blob in the right direction. For more, check out this excellent thread by one of the authors. (Image and research credit: Y. Ozkan-Aydin et al.; via S. Bhamla; submitted by Maximilian S.)

  • Flexible Wings Aid Butterfly Flight

    Flexible Wings Aid Butterfly Flight

    Butterflies are some of the oddest flyers of the insect world, given the large size of their wings relative to their bodies. That could be a recipe for inefficient flight, but a new study shows that butterflies’ large flexible wings actually help them take off quickly.

    When lifting their wings, butterflies use an unusual clapping motion, with the leading edges of their wings coming together before the rest of the wings. This motion helps cup and direct air, creating most of the butterfly’s thrust, according to the researchers. The wings’ flexibility is key to this. Using artificial wings — both stiff and flexible — researchers found that the flexible wings generated 22% more useful impulse and were 28% more efficient. For a tiny flyer with frequent take-offs, that’s an enormous savings! (Image, video, and research credit: L. Johansson and P. Henningsson; via BBC; submitted by Kam-Yung Soh)

  • Adjusting for Gusts

    Adjusting for Gusts

    In flight, birds must adjust quickly to wind gusts or risk crashing. Research shows that the structure of birds’ wings enables them to respond faster than their brains can. The wings essentially act like a suspension system, with the shoulder joint allowing them to lift rapidly in response to vertical gusts. This motion keeps the bird’s head and torso steady, so they can focus on more complex tasks like landing, obstacle avoidance, and prey capture. (Image and research credit: J. Cheney et al.; submitted by Kam-Yung Soh)

  • The Best of FYFD 2020

    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:

    1. Juvenile catfish collectively convect for protection
    2. Gliding birds get extra lift from their tails
    3. How well do masks work?
    4. Droplets dig into hot powder
    5. Updating undergraduate heat transfer
    6. Branching light in soap bubbles
    7. Boiling water using ice water
    8. Concentric patterns on freezing and thawing ice
    9. Bouncing off superhydrophobic defects
    10. 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)

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    Hummingbird Flight in Slow Motion

    Hummingbirds are impressive, acrobatic flyers. Their figure-8 wing stroke pattern produces about 70% of their lift on the downstroke, and the remainder during the backward upstroke. But their tails and body motions also play an important role in stabilizing them, especially in gusty winds. They also have some impressive feeding dynamics. Altogether, they’re one of the most precise flyers in the animal kingdom! (Video and image credit: BBC Earth)

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