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Search results for: “flow visualization”

  • Bubble Tricks

    [original media no longer available]

    Everyone remembers playing with soap bubbles as a child, but most of us probably never became as adept with them as magician Denis Lock. In this video, Lock shows off some of the clever things one can do with surface tension and thin films. My favorite demo starts at 1:25, when he constructs a spinning vortex inside a bubble. He starts with one big bubble and adds a smaller, smoke-filled one beneath it. Then, using a straw, he blows off-center into the large bubble. This sets up some vorticity inside the bubble. When he breaks the film between the two bubbles, the smoke mixes into the already-swirling air in the larger bubble. Then he pokes a hole in the top of the bubble. Air starts rushing out the deflating bubble. As the air flows toward the center of the bubble, it spins faster because of the conservation of angular momentum and a miniature vortex takes shape.  (Video credit: D. Lock/Tonight at the London Palladium/ via J. Hertzberg)

  • Shelf Cloud

    Shelf Cloud

    Sydney, Australia was treated to a spectacular meteorological show over the weekend when an impressive shelf cloud swept over the city. These timelapses show the dramatic leading edge of the incoming thunderstorm. Notice how the cloud streams upward along the shelf. The storm is driven by this updraft of warm moist air, which rises until it is capped by the troposphere. At this point, the air spreads, creating an anvil-like shape, and cools. The moisture drawn up at the storm’s front will condense, freeze, and fall as rain or hail. When the updraft weakens, the storm will be dominated by the downdraft of the falling precipitation and eventually peter out. (Image credit: W. Reed and H. Vann, source; via J. Hertzberg)

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    Mediterranean Currents

    Ocean currents play a major role in the weather and climate of our planet. This video shows a simulation of the surface ocean currents in the Mediterranean and Atlantic over an 11-month period. Each second corresponds to 2.75 days. You’ll see many swirling eddies in the Mediterranean and more flow along the coastlines in the Atlantic. One observation worth noting: near the end of the video, you’ll notice that flow through the Strait of Dover between England and France changes its direction, flowing back and forth depending on tidal forces. In contrast, flow through the Strait of Gibraltar is always into the Mediterranean (within the timescale of the simulation, at least). This net in-flow to the Mediterranean is due in part to the warm waters there evaporating at a higher rate than the cooler Atlantic. (Video credit: NASA; via Flow Viz; h/t to Ralph L)

  • Turbulent Convection

    Turbulent Convection

    These golden lines reveal the complexity of turbulent convective flow. They come from a numerical simulation of turbulent Rayleigh-Benard convection, a situation in which fluid trapped between two plates is heated from below and cooled from above. This situation would typically create convection cells similar to those seen in clouds or when cooking. Inside these cells, warm fluid rises to the top, cools, and sinks down along the sides. With large enough temperature differences, instabilities will occur and cause the flow to become turbulent so that the clear structure of convection cells breaks down into something more chaotic. Such is the case in this simulation. This visualization shows skin friction on the bottom (heated) plate in a flow of turbulently convecting liquid mercury. The bright lines are areas with large velocity changes at the wall, an indication of high shear stress and vigorous convective flow. (Image credit: J. Scheel et al.; via Gizmodo)

  • Psychedelic Cymatics

    Psychedelic Cymatics

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    Cymatics are the visualization of vibration and sound. Here photographer Linden Gledhill has taken a simple speaker vibrating a dish of water and turned it into some incredible art. When you vibrate liquids like water up and down, it disturbs the usually flat air-water interface and creates waves on the surface. These Faraday waves are a standing wave pattern that differs depending on which sound is being played. By combining the wave patterns with LED lighting and strobe effects, Gledhill creates some remarkable images that combine sound, light, and fluid dynamics all in one. If you watch the video (make sure to hit the HD button!), you’ll see the patterns in motion and hear the sounds used to generate them. In the last clip (around 0:19), he’s added glitter to the set-up, which highlights the circulation within the vibrating fluid. As you can see, there are strong recirculating regions in each lobe of the pattern, but other areas, like the center region are almost entirely stationary. You can see more photos from the project in his Flickr feed. Special thanks to Linden for letting me post the video of his work, too! (Video and image cred

    its and submission: L. Gledhill)

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    Bullet-Time Inferno

    Remember the bullet time effect from The Matrix? This spectacular video gives you a similar effect with the turbulent flames created by firebreathers. To capture this level of detail, Mitch Martinez uses an array of 50 cameras placed around the performers, allowing him to reconstruct the full, three-dimensional representation of the flames. Similarly, some scientists use arrays of high-speed video cameras to collect 3D, time-resolved data about phenomena like combustion. Because these flows are so complex in terms of their fluid dynamics and chemistry, capturing full 3D data is important to help understand and model the flow better. (Video credit: M. Martinez; via Rakesh R.)

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    The Upside-Down Jellyfish

    The upside-down jellyfish Cassiopea lives along the sea bottom in coastal regions. As its name suggests, the jellyfish rests upside-down with its bell against the sea floor and its frilly oral arms pointed upward. This jellyfish is a filter feeder, and it draws water up and through its arms by pulsing its bell. The video above visualizes this flow using dye. Each pulse propels fluid up through the arms and draws in fresh water from the surroundings. The frilly arms break up any large vortices from the pulsed flow and diffuse the filtered water as it moves upward. (Video credit: Applied Fluid Mechanics Laboratory at Oklahoma State University)

  • Rowing Water Striders

    Rowing Water Striders

    Water strider insects are light enough that their weight can be supported by surface tension. For some time, they were thought to propel themselves by using their long middle legs to generate capillary waves–ripples– that pushed them forward, but juvenile water striders are too small for this technique to work. Instead researchers found that water striders move by using their middle legs like oars. The leg motion creates vortices about 4 mm below the water surface, and this water moving backward propels the insect forward. In the photos above, the scientists visualized the flow by sprinkling thymol blue on the water and letting the striders move freely. You can learn more about the work here or in this Science Friday episode. (Photo credits: J. Bush et al.)

  • Interrupting Sediments

    Interrupting Sediments

    The pier at Progreso extends 6.5 kilometers into the Gulf of Mexico, creating an artificial obstruction to ocean flow and sediment transport near the shore. The first 2 kilometers of the pier are built on arches that allow some flow through, but the newer sections do not. Prevailing winds act from the east-northeast, driving flow roughly right to left in the image. The sediment traces flow around the pier and reveals the complicated flow-shadow downstream of the newer parts of the pier. (Image credit: NASA Earth Observatory)

  • Vertical-Axis Wind Turbines

    Vertical-Axis Wind Turbines

    Vertical-axis wind turbines (VAWT) are an alternative to traditional wind turbine designs. Unlike their more common cousins, VAWTs rotate about a vertical axis and are omni-directional, meaning that they do not have to be pointed into the wind to produce power. While their size allows VAWTs to be packed much closer to one another than traditional turbines, a clear understanding of the flow around the turbines is needed in order to place the turbines for effective and efficient operation. The images above show the complicated and turbulent wake of a three-bladed VAWT when stationary (top) or rotating (bottom). The flow is visualized using a gravity-driven soap film (flowing left to right in the images) pierced by a model VAWT (seen at the left). The wakes contain many scales from simple, periodically-shed vortices off a blade to very large-scale vortical structures forming downstream of the turbine. This work originally appeared as a poster in the Gallery of Fluid Motion at the 2014 APS DFD Annual Meeting. (Image credit: D. Araya and J. Dabiri)

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