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Tag: soap bubbles

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    “Winter’s Magic”

    Don Komarechka’s beautiful short film, “Winter’s Magic,” captures the beauty of soap bubbles as they freeze. It’s a delicate process and one difficult to capture in video. The bubble freezes first at the bottom, where it touches the cold surface – in this case, snow. That freezing releases latent heat and creates a temperature gradient along the thin liquid film. With that temperature gradient comes a variation in surface tension, and it’s this that creates the flow that lifts the ice crystals from the surface and turns the bubble into a snow globe. Eventually, as the frozen crystals continue growing, flow in the bubble walls comes to halt as the film solidifies.

    For more on the physics of freezing bubbles, check out this interview with the researchers, or, to learn more on how to film freezing bubbles, check out Komarechka’s description. (Video and image credit: D. Komarechka; via Laughing Squid; h/t to Jennifer O.)

  • Inside a Bubble Wall

    Inside a Bubble Wall

    Schlieren photography has an almost magical feeling to it because it enables us to see the invisible – like shock waves and the tiny currents of heat that rise from our skin. But it can also reveal new perspectives on things that aren’t invisible. Here we see soap bubbles viewed through the lens of a schlieren set-up. Schlieren is sensitive to small changes in density, so instead of appearing in their usual rainbow iridescence, the bubbles look glass-like and filled with tiny currents and bubbles. What we’re seeing are some of the many tiny flow variations across the surface of a soap bubble. They’re driven by a combination of forces – gravity, temperature, and surface tension variations, to name a few. Seen in video, you can really appreciate just how dynamic a thin soap film is! (Image credit and submission: L. Gledhill, video version, more stills)

  • The Challenges of Blowing Bubbles

    The Challenges of Blowing Bubbles

    Although every child has experience blowing soap bubbles with a wand, only in recent years have scientists dedicated study to this problem. It turns out to be a remarkably complex one, with subtleties that can depend on the size of the wand relative to the jet a bubble-blower makes as well as the speed at which the air impacts the film. A recent study found that, at low or
    moderate speeds, the film takes on a stable, curved shape (top image), but once you increase to a critical speed, the film will overinflate and burst. The key to forming a bubble, the authors suggest, is hitting that critical speed only briefly; if you slow down before the film ruptures, then the bubble has a chance to disconnect and form a sphere without breaking. 

    The work also suggests there are two reliable methods for bubble making in this way. One is to impulsively move the wand through the background fluid, as shown in the lower animation. The other is the one familiar to children: blow a jet just fast enough to overinflate the film, then let up so the bubble forms without breaking. (Image and research credit: L. Ganedi et al.; via Ars Technica; submitted by Kam-Yung Soh)

  • 2D Turbulence

    2D Turbulence

    Turbulence, the chaotic regime of fluid dynamics, is a complicated beast. It’s hard to analyze or predict, but we do understand some general ideas about it, like the fact that energy starts out in large eddies, cascades down smaller and smaller ones, and finally gets dissipated at the smallest scales, where viscosity snuffs them out. But that’s only true in three dimensions.

    Two-dimensional turbulence – what you get when you confine your fluid to a flat plane – is even weirder. When turbulence is flat, you can actually get an inverse energy cascade, where the energy of small eddies can add up to feed bigger ones. For awhile, this was treated as a mathematical curiosity; after all, we live in a three-dimensional world. But there are situations in life that are nearly two-dimensional, like the surface of a soap bubble or the atmosphere of a planet (which is typically exceptionally thin compared to the planet’s radius). And, little by little, scientists are collecting evidence that this inverse cascade – a flow of energy from small scales to larger ones – does actually happen in the real world. Understanding how this works may explain why hurricanes can intensify even when conditions are “wrong” and how Jupiter’s Great Red Spot has persisted for centuries. To learn more, check out Quanta Magazine’s full article on the work. (Image credit: NASA et al., M. Appel; via Quanta; submitted by Kam-Yung Soh)

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    Bubble Art

    Everyone loves soap bubbles, and bubble artist Melody Yang reveals how to make some pretty awesome ones in this video for Wired. The surface tension of bubbles makes them naturally seek a shape that minimizes their surface area relative to the volume they contain. For a single bubble, that’s a sphere. But once you start joining multiple bubbles, as Yang demonstrates, that minimal surface area can change, even to something unexpected like a cube.

    Bubbles also have an impressive ability to self-heal. As long as whatever passes through them is wet – whether it’s a hand, a straw, or even a ball bearing – the soap film will probably heal itself rather than break. This is a key feature for many of Yang’s tricks, including the impressive planetary bubble. (Video credit: Wired; image credits: Wired/Colossal; via Colossal)

  • Soapy Rainbows

    Soapy Rainbows

    The swirling psychedelic colors of a soap bubble come from the interference of light rays bouncing off the inner and outer surfaces of the film. As a result, the colors we see are directly related to the thickness of the soap film. Over time, as a film drains, black spots will appear in it. This happens where the bubble’s wall becomes thinner than the wavelength of visible light. Black spots will grow and merge as the film continues to thin. Then, when it’s too thin to hold together any longer, the bubble will pop and disappear. (Image credit: L. Shen et al., source)

  • Liquid Sculptures

    Liquid Sculptures

    With patience and timing, one can create remarkable sculptures with fluids. To capture this shot, Moussi Ouissem used two droplets, perfectly timed. The first fell through the soap bubble (which stayed intact thanks to its powers of self-healing) and hit the pool of water. The impact caused a cavity, which then inverted into a Worthington jet. The second drop was timed to impact the column of the jet, creating the saddle-shaped splash seen here. Ripples in the bubble are still visible from the passage of the second drop, and several satellite droplets are signs of the violence of the impacts. (Image credit: M. Ouissem)

  • Self-Healing Bubbles

    Self-Healing Bubbles

    Soap films have the remarkable property of self-healing. A water drop, like the one shown above, can pass through a bubble (repeatedly!) without popping it. This happens thanks to surfactants and the Marangoni effect. Surfactants are molecules that lower the surface tension of a liquid and congregate along the outermost layer of a soap film. When water breaks through the soap film, its lack of surfactants causes a higher surface tension locally. This triggers the Marangoni effect, in which flow moves from areas of low surface tension toward ones of high surface tension. That carries surfactants to the region where the drop broke through and helps stabilize and heal the soap film. Incidentally, the same process lets you stick your finger into a bubble without popping it as long as your hand is wet! (Image credit: G. Mitchell and P. Taylor, source)

  • Supporting Bubbles

    Supporting Bubbles

    Surface tension holds small droplets in a partial sphere known as a spherical cap. But when droplets become larger, they flatten out into puddles due to the influence of gravity. In contrast, soap bubbles remain spherical to much larger sizes. The bubble pictured above, for example, is more than 1 meter in radius and nearly 1 meter in height.

    There is a maximum height for a soap bubble, though, and it’s set by the physical chemistry of the surfactants used in the soap. To support itself, the bubble requires a difference in surface tension between the top and bottom of the bubble. A higher surface tension is necessary at the top of the bubble to help prevent fluid from draining away. The difference in surface tension between the top and bottom of the bubble can never be greater than the difference in surface tension between pure water and the soap mixture – thus those values set a maximum height for a bubble. The researchers found their bubbles maxed out at a height of about 2 meters, consistent with their theoretical predictions. (Image credit: C. Cohen et al.; via freshphotons)

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    Freezing Bubbles

    Soap bubbles are wonderfully ephemeral, their surfaces constantly in motion as air currents, surface tension variations, and temperature differences make them dance. In this video, though, photographer Paweł Załuska focuses on freezing soap bubbles. Watching the growth of ice crystals across the bubbles’ thin surface is mesmerizing. Snowflake-like crystals can nucleate anywhere on the film and, as in the sequence at 0:48, those crystals can float around on the bubble’s surface like snowflakes drifting on a breeze until enough of the film solidifies to bring the bubble to a halt and, then, a collapse. (Video credit: P. Załuska/ZALUSKart; via Gizmodo)