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Search results for: “flow visualization”

  • “Ornitographies”

    “Ornitographies”

    If birds left trails in the sky, what would they look like? This is the question that haunted photographer Xavi Bou and inspired him to create his “Ornitographies” series. Using video of birds in flight, he combines frames to construct these snapshots of flight. In them, birds become streaklines feathered with wingbeats.

    I love how the technique highlights the patterns of flapping flight. A bird flying steadily over a lake becomes a wavy line with consistent, perfectly matched up- and downstrokes, whereas a bird just taking off has short, fast wingbeats that slowly lengthen and steady out as the bird gets aloft. Flocks of birds turn into a tornado of swirling lines as they land or take-off en mass. (Image credit: X. Bou; via Flow Vis)

  • Trails from a Delta Wing

    Trails from a Delta Wing

    Top-down view of green and red dyes streaming off a delta wing

    Rhodamine (red) and fluorescein (green) dyes highlight the complex flows around a delta wing. To visualize the flow, researchers painted the apex of the delta wing with rhodamine, which gets drawn into the core of the wing’s leading edge vortex. The green fluorescein dye was added to the wing’s trailing edge, where it gets pulled into the secondary structure of the vortices. A laser illuminates the flow, making even the most delicate wisps of dye shine. As the wake behind the wing develops, the dyes reveal growing instabilities along the vortices. Given time and space, these instabilities will grow large enough to destroy any order in the wake, leaving behind turbulence. (Image and research credit: S. Morris and C. Williamson; see also poster)

  • Ferrofluid in a Cell

    Ferrofluid in a Cell

    Ferrofluids are a colloid consisting of magnetically sensitive nanoparticles suspended in a carrier liquid, like oil. They’re often associated with a distinctive spiky appearance when exposed to a magnet, but this isn’t their only magnetic response. Above we see a ferrofluid confined to a Hele-Shaw cell – essentially two glass plates with a small gap between them. In the upper image, the ferrofluid is exposed first to an axial magnetic field, which stretches it to form spidery arms. Then the magnetic field switches to a rotating configuration, which curls the arms around and causes the ferrofluid to slowly rotate.

    In the lower image, you see the reverse. First, the ferrofluid feels a rotating magnetic field. When this is changed to an axial field, the ferrofluid bursts into a cell-like center with straight arms. As the magnitude of the axial field increases further, the arms begin to curl. For more fantastical ferrofluid formations, check out these previous posts featuring artists Linden Gledhill and Fabian Oefner. (Image credit: M. Zahn and C. Lorenz, source; via Ashlyn N.)

  • Phytoplankton Swirls

    Phytoplankton Swirls

    A winter bloom of phytoplankton appears as green and teal swirls in this false-color satellite image of the Gulf of Aden. Although phytoplankton can be an important food source for fish and other marine animals, in recent years we’ve observed more frequent toxic blooms. Currently, physical sampling of the phytoplankton is necessary to determine what type they are, but scientists are working to use multi-spectral imaging to identify different species remotely. As harmful as they can be, blooms like these help visualize the flow and mixing in different coastal regions. Here, for example, we can see distinctive turbulent eddies in the Gulf that are tens of kilometers across. (Image credit: N. Kuring/NASA; via NASA Earth Observatory)

  • Order in Chaos

    Order in Chaos

    Although turbulent flow is chaotic, it’s not completely disordered. In fact, order can emerge from turbulence, though exactly how this happens has been a long-enduring mystery. Take the animations above. They show the flow that develops between two plates moving in opposite direction that are separated by a small gap. (The formal name for this is planar Couette flow.) The visualization is taken in a plane at a fixed height between the plates.

    Initially (top), the flow shows narrow bands of turbulence, shown in green, separated by calmer, laminar zones in black. As time passes, these areas of laminar and turbulent flow self-organize, eventually forming diagonal stripes that are much longer than the gap between plates (bottom), the natural length-scale we would expect to see in the flow. Researchers have wondered for years why these distinctive stripes form. What sets their spacing, and why are they along diagonals?

    To answer those questions, researchers explored the full Navier-Stokes equations, searching for equilibrium solutions that resemble the striped patterns seen in experiments and simulation. And for the first time, they’ve found a mathematical solution that matches. What the work shows is that the pattern emerges naturally from the equations; in fact, given the characteristics of the solution, the researchers found that many disturbances should lead to this result, which explains why the pattern appears so frequently. (Image and research credit: F. Reetz et al., source; via phys.org; submitted by Kam-Yung Soh)

  • Powdery Trails

    Powdery Trails

    Because air and water are colorless and transparent, we cannot see most of the flows around us – but they’re always there. In a recent series, photographer Jess Bell has been capturing images of jumping dogs trailing a colorful powder wake. There’s no compositing in the photos. Bell puts powder on the dogs, then photographs them as they jump. The results show the billowing, turbulent wakes left by the dogs. I particularly like how you can see the stream of powder coming from some of the dogs’ ears. For more of Bell’s work, check out her website and Instagram. (Image credit: J. Bell; via PetaPixel and Rakesh R.)

  • Vortices and Ground Effect

    Vortices and Ground Effect

    Though typically unseen, the vortices that swirl from the tips of aircraft wings are powerful. Here you see a Hawker Sea Fury equipped with a smoke system used to visualize the vortices that form at the wingtip as high-pressure air from the bottom of the wing and low-pressure air from the top swirl together. As you can see, the vortices persist in the wake long after the plane passes. The size and strength of the vortices depend on the size and speed of the aircraft; this is why air traffic control requires smaller planes to wait longer to take off or land if there was just a larger aircraft on the runway.

    The other cool thing to note here is how the wingtip vortices move apart from one another in the animation above. In flight, wingtip vortices usually stay roughly parallel to one another, but they drift downward in the aircraft’s wake. Near the ground, though, the vortices cannot move down, so instead ground effect forces them apart from one another, as seen here. (Image and video credit: E. Seguin; via Kelsey C.)

  • Waves

    Waves

    Photographer Ray Collins is known for his striking portraits of waves, some of which I’ve featured on previous occasions. Collins is colorblind, so he focuses heavily on shape and texture in the wave, which produces some stunningly dramatic views of moving water frozen in time. There’s great power and beauty in breaking waves, and researchers are still actively learning just how significant they are to our planet’s cycles. 

    Note the spray blurring the edges of every wave here; these are some of the largest droplets the wave will make. As it crashes forward, the wave traps pockets of air, and, as those bubbles burst, they will create a spray of tinier droplets that carry moisture and salt into the atmosphere to seed clouds and, eventually, rain.

    Collins’ work reminds us both of the ocean’s power and its fragility as it undergoes rapid changes due to humanity’s influence. For more photos as well as a great interview with Collins, check out My Modern Met. (Image credit: R. Collins; via My Modern Met and James H.)

  • Blackwater Rivers

    Blackwater Rivers

    Blackwater rivers, like the Suwannee River in Florida, carry waters so laden with organic material that they’re dyed a deep, dark brown. For the Suwannee, most of this material comes from the rich peat deposits of the Okefenokee Swamp that lies upstream. As vegetation in the swamp decays, tannins from the plants dissolve into the water, giving it its distinctive color, which the river maintains along its full 400-kilometer journey to the Gulf of Mexico. The dark waters of the river act as a tracer, revealing how the fresh river water mixes with the ocean in the enhanced-color satellite image above. It’s amazing to see how far the river’s influence spreads before delicate wisps of color pierce the darkness. (Image credit: U.S. Geological Survey; via NASA Earth Observatory)

  • Featured Video Play Icon

    “If I Say”

    The new Mumford & Sons single “If I Say” features a fluid-dynamical music video. It’s full of dendritic fingers and flowing colors – likely from combinations of inks, paints, and other fluids. Although the fingers are reminiscent of the viscosity-dependent Saffman-Taylor instability, these appear to be driven by variations in surface tension between the different fluids. That’s a major feature throughout the video; although some of the flow is caused by the syringes depositing fluids, much of it seems to be a Marangoni effect, where flow moves away from areas of low surface tension to ones with higher surface tension. (Video credit: Mumford & Sons; filmed by P. Hofstede; via Katie M.)

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