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Search results for: “droplet”

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    The World in a Droplet

    Capturing refracted images in a droplet is a popular pastime among high-speed photographers, and in this solo Slow Mo Guy outing, we get to see that process in video. Physically, the subject is a simple drop of water, which on impact with a pool, rebounds into a Worthington jet and ejects one or more droplets from its tip. Despite hundreds of years of study, it’s still a joy to watch, especially at 12,000 frames per second.

    It’s also not the easiest image to capture, and one thing I rather enjoy about this video is how it gives you a sense of the trial and error involved in capturing just the right view. Even without having to worry about the timing issues, there is a lot of fiddling with lenses, focus, lights, and positioning — something familiar not just to photographers and videographers but to many researchers as well! (Image and video credit: The Slow Mo Guys)

  • Droplet Surface Jets

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    Coalescence in Heavy Metal Droplets

    When a drop of water falls into a pool, it doesn’t always coalesce immediately. Instead, it can go through a coalescence cascade in which the drop partially coalesces, a daughter drop bounces off the surface, settles, and itself partially coalesces. We’ve seen this many times before, but today’s video shows something a little different: here the drop and pool in question are made of a gallium alloy immersed in a background of sodium hydroxide. This means that the drop has very high surface tension (and density) but does not form an oxidation layer on its surface that could inhibit coalescence. And just like the water droplet, the gallium alloy undergoes a series of partial coalescences.

    A heavy metal droplet undergoes partial coalescence with a pool of the same liquid.

    There’s one key difference, though. Did you notice that the water droplets bounce higher as the drops get smaller, but the gallium droplets do the opposite? Previous research suggested that the droplet rebound height is driven by capillary forces, but the high surface tension of both of these liquids means that capillary forces should be large for both of them. Perhaps there’s much more viscous drag in the gallium and sodium hydroxide case? (Image, video, and research credit: R. McGuan et al.)

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    Superwalking Droplets

    Vibrate a pool of silicone oil and you can generate walking droplets. Drive the vibration at two simultaneous frequencies and you can support much larger droplets, known as superwalkers. These superwalkers have their own intriguing dynamics, a few of which are featured in this video.

    Superwalkers can create promenading pairs, chase one another, orbit, and even form ordered and disordered crystals. They can even generate stop-and-go traffic patterns. As with regular walkers, these complex behaviors come from the interaction of bouncing droplets with their ripples and those of their neighbors. (Image, video, and research credit: R. Valani et al.)

  • Droplet Bounce

  • Digging Droplets

  • Transporting Droplets

  • Droplet Circulation

  • Manipulating Droplets

  • Droplet Bounces

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