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Search results for: “art”

  • A Water Balloon on a Bed of Nails

    A Water Balloon on a Bed of Nails

    If you dropped a water balloon on a bed of nails, you’d expect it to burst spectacularly. And you’d be right – some of the time. Under the right conditions, though, you’d see what a high-speed camera caught in the animation above: a pancake-shaped bounce with nary a leak. Physically, this is a scaled-up version of what happens to a water droplet when it hits a superhydrophobic surface.

    Water repellent superhydrophobic surfaces are covered in microscale roughness, much like a bed of tiny nails. When the balloon (or droplet) hits, it deforms into the gaps between posts. In the case of the water balloon, its rubbery exterior pulls back against that deformation. (For the droplet, the same effect is provided by surface tension.) That tension pulls the deformed parts of the balloon back up, causing the whole balloon to rebound off the nails in a pancake-like shape. For more, check out this video on the student balloon project or the original water droplet research. (Image credits: T. Hecksher et al., Y. Liu et al.; via The New York Times; submitted by Justin B.)

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  • Shot Through a Drop

    Shot Through a Drop

    Shoot a sphere through a drop with sufficient speed, and you’ll see something like the composite photo above. Going from right to left, the projectile is initially coated in liquid and stretches the fluid behind it as it continues flying. This forms a thin sheet of fluid called a lamella with a thicker, uneven rim at its far end. The lamella continues stretching until the projectile breaks through and detaches. Now the lamella starts rebounding back on itself as surface tension struggles to keep the fluid together. A new rim forms on the front, and both the front and back rims thicken as the lamella collapses. Along the rims thicker portions start forming droplets – like spikes on a crown – as the surface-tension-driven Plateau-Rayleigh instability starts breaking the structure down. The untenable sheet of fluid will break up into a cloud of smaller, satellite droplets when it can hold together no longer. (Image credit: V. Sechenyh et al., video)

  • Crowns On Impact

    Crowns On Impact

    Dropping a partially-filled test tube of water against a table makes the meniscus at the air-water interface invert into a jet of liquid. In some cases, the impact is strong enough to generate splashing crowns of water around the base of the jet. These crowns come in two forms – one with many splashes layered upon one another and the other with only a few splashes and a faster jet. 

    The many-layered splash crowns come from the pressure wave that reflects back and forth from the bottom of the tube to the surface and back. This pressure wave moves at the speed of sound and vibrates the water surface, creating the many splashes. The same reflected pressure wave occurs in the second type of splash crown, but it gets disrupted by cavitation bubbles that form in the water (visible in the lower left image). Instead the splash crowns form from the shock waves generated when the cavitation bubbles collapse. (Image credits: A. Kiyama et al.)

  • Sedimentary Swirls

    Sedimentary Swirls

    Sediment swirls in Bear Lake caught the eye of an astronaut aboard the International Space Station last year. Bear Lake is situated in the Rocky Mountains, on the Idaho-Utah border. The eddies in the center of the lake are each about 3 km across and are likely the result of inflow from the lake’s tributaries. Silt and sediment picked up by the rivers and streams gets deposited into Bear Lake, revealing the turbulent mixing of tributary waters with those already in the lake. (Image credit: NASA; via NASA Earth Observatory)

  • The Best of FYFD 2016

    The Best of FYFD 2016

    2016 was a wild ride here at FYFD, full of lots of travel and crazy things like making the New York Times and doing radio interviews. I also revamped the YouTube channel and went full-time doing science communication. But let’s look at what you thought was the best part of FYFD’s 2016 based on the most popular posts of the year:

    1. The physics of chocolate bonbons and other poured coatings
    2. What makes this octopus kite look so realistic?
    3. Shooting oobleck with a golf ball
    4. Buckling of a crown splash
    5. Lava as a gravity current
    6. Microscale rockets could aid with drug delivery
    7. How prairie dogs keep the air in their burrows fresh
    8. Why molten aluminum slides right off dry ice
    9. The dangers of underwater explosions
    10. Skipping an elastic ball off water

    Special congrats to The Backyard Scientist and The Splash Lab – both of whom earned multiple spots in the top 10 with their awesome physics-filled visuals. Stay tuned in 2017 for more great fluid dynamics, and if you’d like to help support what I do with FYFD, consider becoming a patron or making a one-time donation!

    (Image credits: MIT News; E. Chew; The Backyard Scientist; J. Marston et al.; J. Tarsen; J. Li et al.; N. Sharp; The Backyard Scientist; M. Rober; J. Belden et al.)

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    Why Ice is Slippery

    Ice is slippery. This is a fundamental fact we humans have dealt with so often that we rarely take the time to ask why. Other solids aren’t inherently slippery, so what is it that makes ice so? Remarkably, scientists only began to ask this question and propose theories within the past couple hundred years. One common suggestion is that the high pressure of an ice skate on ice locally melts the ice, creating a thin liquid layer a skater glides across. But this does not explain why ice is slippery for shoes or tires, nor why it’s possible to ice skate at more than a few degrees below freezing. Several other effects may be in play, such as frictional heating or the peculiar molecular forces between water molecules. Current research suggests that ice has a thin liquid layer tens or hundreds of nanometers thick that causes its slippery nature. For a great review of the subject, see Robert Rosenberg’s Physics Today article. (Video credit: SciShow)

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    Paint Spilling Physics

    There is a remarkable amount of physics contained in art. In this video, scientists from The Splash Lab explore some of the physics involved in pouring paint atop a rectangular post. The spreading paint transforms its shape repeatedly, and, at the corners of the post, it preserves a tiny history of all the colors poured. Paint sliding down the sides shifts from a thin sheet to a thicker jet that deposits color in waves. For tall posts, the distance the paint falls is long enough for instabilities to set in, producing a paint puddle that’s riddled with curves and waves between each color of paint. It’s a lovely reminder of the complexity inherent even within a simple action. (Video credit: R. Hurd et al.)

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    Growing Snowflakes

    Watching a snowflake grow seems almost magical–the six-sided shape, the symmetry, the way every arm of it grows simultaneously. But it’s science that guides the snowflake, not magic. Snowflakes are ice crystals; their six-sided shape comes from how water molecules fit together. The elaborate structures and branches in a snowflake are the result of the exact temperature and humidity conditions when that part of the snowflake formed. The crystals look symmetric and seem to grow identical arms simultaneously because the temperature and humidity conditions are the same around the tiny forming crystals. And the old adage that no two snowflakes are alike doesn’t hold either. If you can control the conditions well enough, you can grow identical-twin snowflakes! (Video credit: K. Libbrecht)

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    Visualizing Flow with Snowfall

    One of the challenges in engineering and operating wind turbines is that full-scale turbines rarely behave as predicted in smaller-scale laboratory experiments and simulations. One way to reconcile these differences (and discover what our experiments and simulations are missing) is to take the experiments out into the field. One research group has done this by using snowfall to visualize the flow around wind turbines. In this video, they share some of their observations, which include interactions of tip vortices with one another and with the vortex from the tower. My favorite part starts around 1:50 where you can observe tip vortices leap-frogging one another behind the wind turbine! (Video credit: Y. Liu et al.)

  • CYGNSS

    CYGNSS

    Yesterday marked the launch of a new constellation of eight microsatellites, the Cyclone Global Navigation Satellite System (CYGNSS), designed to monitor hurricanes in Earth’s tropics. The constellation will provide unprecedented capability to monitor conditions inside hurricanes–information that will hopefully help scientists improve hurricane prediction models. Each CYGNSS microsat monitors GPS signals that it receives from the GPS satellite system and from the reflection of that signal off the Earth. By comparing these signals, the satellites can determine wave heights in the ocean, and from that wave information, they can measure surface wind speeds. By peering inside the hurricane as it forms and travels, scientists hope they will be better able to estimate not only a hurricane’s path but how strong it will be when it makes landfall. (Image credits: NASA)

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