Tag: fluid dynamics

Flamingo Fluid Dynamics, Part 1: A Head in the Game
Flamingos are unequivocally odd-looking birds with their long skinny legs, sinuous necks, and bent L-shaped beaks. They are filter-feeders, but a new study shows that they are far from passive wanderers looking for easy prey in shallow waters. Instead, flamingos are active hunters, using fluid dynamics to draw out and trap the quick-moving invertebrates they feed on. In today’s post, I’ll focus on how flamingos use their heads and beaks; next time, we’ll take a look at what they do with their feet.
Feeding flamingos often bob their heads out of the water. This, it turns out, is not indecision, but a strategy. Lifting its flat upper forebeak from near the bottom of a pool creates suction. That suction creates a tornado-like vortex that helps draw food particles and prey from the muddy sediment.
When feeding, flamingos will also open and close their mandibles about 12 times a second in a behavior known as chattering. This movement, as seen in the video above, creates a flow that draws particles — and even active swimmers! — toward its beak at about seven centimeters a second.
Staying near the surface won’t keep prey safe from flamingos, either. In slow-flowing water, the birds will set the upper surface of their forebeak on the water, tip pointed downstream. This seems counterintuitive, until you see flow visualization around the bird’s head, as above. Von Karman vortices stream off the flamingo’s head, which creates a slow-moving recirculation zone right by the tip of the bird’s beak. Brine shrimp eggs get caught in these zones, delivering themselves right to the flamingo’s mouth.
Clearly, the flamingo is a pretty sophisticated hunter! It’s actively drawing out and trapping prey with clever fluid dynamics. Tomorrow we’ll take a look at some of its other tricks. (Image credit: top – G. Cessati, others – V. Ortega-Jimenez et al.; research credit: V. Ortega-Jimenez et al.; submitted by Soh KY)
Fediverse Reactions
June 3, 2025
How Insects Fly in the Rain
Getting caught in the rain is annoying for us but has the potential to be deadly for smaller creatures like insects. So how do they survive a deluge? First, they don’t resist a raindrop, and second, they have the kinds of surfaces water likes to roll or bounce off. The key to this second ability is micro- and nanoscale roughness. Surfaces like butterfly wings, water strider feet, and leaf surfaces contain lots of tiny gaps where air gets caught. Water’s cohesion — its attraction to itself — is large enough that water drops won’t squeeze into these tiny spaces. Instead, like the ball it resembles, a water drop slides or bounces away. (Video and image credit: Be Smart)
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June 2, 2025
“Soap Bubble Bonanza
This video offers an artistic look at a soap bubble bursting. The process is captured with high-speed video combined with schlieren photography, a technique that makes visible subtle density variations in the air. The bubbles all pop spontaneously, once enough of their cap drains or evaporates away for a hole to form. That hole retracts quickly; the acceleration of the liquid around the bubble’s spherical shape makes the retracting film break into droplets, seen as falling streaks near the bottom of the bubble. The retraction also affects air inside the bubble, making the air that touched the film curl up on itself, creating turbulence. Then, as the film completes its retraction, it pushes a plume of the once-interior air upward, as if the interior of the bubble is turning itself inside out. (Video and image credit: D. van Gils)
May 30, 2025
Non-Newtonian Effects in Magma Flows
As magma approaches the surface, it forces its way through new and existing fractures in the crust, forming dikes. When a volcano finally erupts, the magma’s viscosity is a major factor in just how explosive and dangerous the eruption will be, but a new study shows that what we see from the surface is a poor predictor of how magma actually flows within the dike.
Researchers built their own artificial dike using a clear elastic gelatin, which they injected water and shear-thinning magma-mimics into. By tracking particles in the liquids, they could observe how each liquid followed on its way to the surface. All of the liquids formed similar-looking dikes at a similar speed, but within the dike, the liquids flowed very differently. Water cut a central jet through the gelatin, then showed areas of recirculation along the outer edges. In contrast, the shear-thinning liquids — which are likely more representative of actual magma — showed no recirculation. Instead, they flowed through the dike in a smooth, fan-like shape.
The team cautions that surface-level observations of developing magma dikes provide little information on the flow going on underneath. Instead, their results suggest that volcanologists modeling magma underground should take care to include the magma’s shear-thinning to properly capture the flow. (Image credit: T. Grypachevska; research credit: J. Kavanagh et al.; via Eos)
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May 29, 2025
The Hidden Beauty in the Mundane
Physicist Sidney Nagel has spent his career on topics that are somewhat unexpected: how coffee stains form, how droplets splash — or don’t, and how fluid flows into viscous fingers. Often this means looking at the mechanics of everyday occurrences that we otherwise take for granted. Instead, Nagel probes carefully at things like a coffee stain, asking why it’s darker at the edges and what he could do to keep that from happening — all to ultimately uncover the forces and mechanisms at play. Quanta has a great little interview with him on this and other topics. Check it out here. (Image credit: S. Nagel and K. Norman; via Quanta)
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May 28, 2025
Whale Migration Carries Nutrients
When it comes to the movement of nutrients in the ocean, we think of run-off from rivers, upwelling along coasts, and convective currents. We don’t typically think about animal migrations, but a new study of baleen whales (including species like humpbacks and right whales) suggests that these massive mammals provide a small but critical spreading service.
These whales feed in cold, nutrient-rich waters, like those in the Arctic, then travel thousands of kilometers to warm but nutrient-poor tropical waters to birth and raise calves. During that time, mothers do not hunt or eat; they live off their fat stores, which they also use to make milk for their offspring. Although they’re not eating during this time, they do still urinate, and it’s this activity that, according to researchers, adds some 3,000 tons of critical nitrogen to these areas. Since nitrogen is often a limited resource in these tropical waters, the whales’ urine may act like a fertilizer shipment for other species in their breeding grounds. (Image credit: C. Le Duc; research credit: J. Roman et al.; via Eos)
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May 27, 2025
Bigger Particles Slide Farther
Mudslides and avalanches typically carry debris of many shapes and sizes. To understand how debris size affects flows like these, researchers use simplified, laboratory-scale experiments like this one. Here, researchers mix a slurry of silicone oil and glass particles of roughly two sizes. The red particles are larger; the blue ones smaller. Sitting in a cup, the mixture tends to separate, with red particles sinking faster to form the bottom layer and smaller blue particles collecting on top. And what happens when such a mixture flows down an incline? The smaller blue particles tend to settle out sooner, leaving the larger red particles in suspension as they flow downstream. (Video and image credit: S. Burnett et al.)
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May 26, 2025
“Now I See – The Collection Vol. 1”
On the heels of his behind-the-scenes introduction, here’s the first volume of artist Roman De Giuli’s “Now I See”. In it, we appear to soar above vast colorful landscapes. Rivers flow past islands. Glaciers creep along valleys. Canyons cut through deserts. It’s like a bird’s eye view of our planet’s terrestrial wonders. (Video and image credit: R. De Giuli)
May 23, 2025
Tracking Insects in Flight
Insects are masters of a challenging flight regime; their agility, stability, and control far outstrip anything we’ve built at their size. But to even understand how they accomplish this, researchers must manage to capture those maneuvers in the first place. Insects don’t stay in one small area, which is what the typical fixed camera motion capture set-up requires. Instead, one group of researchers has designed a system with a moveable mirror that tracks an insect’s motion in real-time, ensuring that the camera stays fixed on the insect even as it traverses a room or — for the drone-mounted version — a field.
Real-time motion tracking means that researchers can better capture detailed footage of the insect’s maneuvers in a lab environment, or they can head into the field to follow insects in the wild. Imagine tracking individual pollinators through a full day of gathering or watching how a bumblebee responds to getting hit by a raindrop mid-flight. (Video and image credit: Science; research credit: T. Vo-Doan et al.)
Fediverse Reactions
May 22, 2025
Fractal Fingers
$Close up image of green-dyed liquid in fractal branches on a clear acrylic surface.$
As bizarre as the branching fractal fingers of the Saffman-Taylor instability look, they’re quite a common phenomenon. In his video, Steve Mould demonstrates how to make them by sandwiching a viscous liquid like school glue between two acrylic sheets and then pulling them apart. The more formal lab-version of this is the Hele-Shaw cell, which he also demonstrates. But you may have come across the effect when pealing up a screen protector or in dealing with a cracked phone screen. In all of these cases, a less viscous fluid — specifically air — is forcing its way into a more viscous fluid, something that it cannot manage without the fluid interface fracturing. (Video and image credit: S. Mould)
Fediverse Reactions
May 21, 2025