FYFD

Videos

  • Paper Marbling

    [original media no longer available]

    Suminagashi, the Japanese art of “floating ink”, is one of many methods historically used for paper marbling. In it, a shallow layer of water or other viscous fluid serve as a medium for drops of ink that diffuse across the fluid surface and are manipulated with straws, brushes, or other tools. Once a design is complete, an absorbent surface like paper or fabric is carefully placed on top to preserve the art.  Among other applications, the technique has historically been used for calligraphy and book bindings.

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    Hydraulic Jumps

    This student video outlines the principles and mathematics behind the hydraulic jump, a commonly occurring phenomenon that occurs when a high velocity liquid flows into a low velocity zone. In order to slow down, the liquid’s kinetic energy converts to potential energy, resulting in an increase in height. Though often seen in kitchen sinks or rivers, the principle is also commonly used in dams and other manmade structures to control erosion of surrounding features. (Video credit: T. Price, D. Alexander, A. Rodabough, and D. Jensen)

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    Atmospheric Dynamics in the Lab

    One way to explore some of the large-scale atmospheric dynamics we observe here on earth is through table-top demonstrations such as this one. Here a platform with a water tank is rotating at a constant velocity. The camera rotates with the tank; this is why the hand in the video seems to spin. At the center of the tank, ice in a can cools the water, while the warmer air along the periphery provides heating. The green dye marks initially cooler fluid while the red dye marks the warmer fluid from the outside of the tank. The dense cooler fluid sinks and moves outward while warmer water moves in to replace it. This creates radial circulation; the thermal gradients and rotation cause the eddies and jets seen from this top view, in much the same way that they form in the mid-latitudes of earth’s atmosphere.  (Video credit: Marshall Lab, MIT)

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    Fire Tornado

    An artificial fire tornado makes for fascinating viewing. The box fans are positioned around a central firepit such that they impart the angular velocity needed to create a vortex. I’ve actually seen an even bigger live demonstration than this one at a fluid dynamics conference.  Do not try this yourself. Fire tornadoes occur in nature, too: take a look at how they form. (submitted by acervant)

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    Sea Surface Temperatures

    This video shows sea surface temperature results and their seasonal variation from a numerical simulation modeling circulation in the atmosphere and oceans. Modeling such enormous problems requires the development of reasonable models of the turbulent physics, clever algorithms to quickly progress the solutions, relatively low-fidelity (a single grid node may cover tens of kilometers), and enormous computing power. (Video credit: NOAA; via Gizmodo)

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    The Chaos of a Bouncing Droplet

    This video explores chaos in a bouncing droplet.  A drop of silicon oil bounces on a vibrating bath of oil; the thin layer of air injected with each bounce between the droplet and bath keeps them from coalescing. Initially, the droplet behaves like a bouncing ball, jumping once per oscillation. As the vibration amplitude increases, the droplet begins making a small jump, then a large jump, then a small jump, and so on. This is called period doubling since the droplet now jumps in a pattern with twice the period of the original and is a hallmark of nonlinear dynamical systems. Further increase in the vibration amplitude leads to chaotic bouncing and occasional ejecta. (Video credit: D. Terwagne et al.)

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    Canyon Fire Timelapse

    Wildfires continue to burn across Colorado and other parts of the United States. This timelapse video shows 5 days worth of the Waldo Canyon fire. Smoke billows through the night and day, with diurnal temperature changes and winds affecting whether the turbulent plumes rise high or hover on the horizon. It is hard to describe the eeriness of watching a fire burn uncontrollably on the horizon; we hope those fighting the fires stay safe and that those affected by the fires are able to return and recover soon. (Video credit: Steve Moraco; submitted by Chris P)

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    How the Sun Drives the Earth

    This video describes how the sun’s energy drives wind and ocean currents on earth. As solar winds stream forth from the sun, our magnetosphere deflects the brunt of the impact (creating auroras at the poles) while the atmosphere, land masses, and oceans absorb thermal energy from the sun’s light. Because of our cycles of day and night and the differences in how land, water, and ice absorb heat, temperature differentials around the earth drive a massive heat engine, causing the circulation of water and wind all around our world. Numerical simulations like the ones underlying this video are vital for the prediction of climate and weather, as well as for developing models and techniques that can be applied to other problems in science and engineering. (Video credit: NASA; via Gizmodo)

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    Traffic Fluid Dynamics

    What does traffic have to do with fluid dynamics? Rather a lot, actually! Many parallels exist between traffic and compressible fluid flow. One such example, the concept of a shock wave, is demonstrated in the video above. As the traffic jam develops, the cars experience sudden changes in their velocity and relative distance (in a fluid, this would be density). This change travels backward through the traffic in the form of a shockwave, just the same as discontinuous changes in a fluid.

    Road construction provides another common example of compressible-flow-like behavior in cars.  For an incompressible fluid like water, reducing the area of a pipe would increase the velocity, but just the opposite happens when a road is reduced from two lanes to one.  Traffic slows down and clumps together. When the road opens back up from one lane to two, suddenly the speed and the distance between cars increases. This is exactly what happens in a rocket nozzle–it’s the expanding bell-like shape that causes air to accelerate supersonically. (Video credit: New Scientist)

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    New CPU Fan

    This video discusses a new quieter and more efficient CPU fan developed by engineers at Sandia National Labs. As the impeller spins, it draws ambient air down the center of the impeller while the shape of the fins forces air past the fins and out radially. As the air flows over the fins, it draws heat from the CPU away. In a sense, the design combines a heat sink with a fan. (Video credit: Sandia National Labs; submitted by Adam L)