#2025gofm — Public Fediverse posts

Jets From Impact

When a test tube of liquid hits a surface, the curvature of the meniscus focuses the rebounding fluid into a jet. In this video, researchers show some of the many variations they’ve explored on these experiments–from changing the depth of the fluid and the shape of the container, to changing the working fluid to honey or to dry grains. It’s a nice introduction to a fascinating phenomenon! (Video and image credit: H. Watanabe et al.; research credit: H. Watanabe et al. and K. Kobayashi et al.)

Jets From Impact

When a test tube of liquid hits a surface, the curvature of the meniscus focuses the rebounding fluid into a jet. In this video, researchers show some of the many variations they’ve explored on these experiments–from changing the depth of the fluid and the shape of the container, to changing the working fluid to honey or to dry grains. It’s a nice introduction to a fascinating phenomenon! (Video and image credit: H. Watanabe et al.; research credit: H. Watanabe et al. and K. Kobayashi et al.)

Jets From Impact

When a test tube of liquid hits a surface, the curvature of the meniscus focuses the rebounding fluid into a jet. In this video, researchers show some of the many variations they’ve explored on these experiments–from changing the depth of the fluid and the shape of the container, to changing the working fluid to honey or to dry grains. It’s a nice introduction to a fascinating phenomenon! (Video and image credit: H. Watanabe et al.; research credit: H. Watanabe et al. and K. Kobayashi et al.)

Jets From Impact

When a test tube of liquid hits a surface, the curvature of the meniscus focuses the rebounding fluid into a jet. In this video, researchers show some of the many variations they’ve explored on these experiments–from changing the depth of the fluid and the shape of the container, to changing the working fluid to honey or to dry grains. It’s a nice introduction to a fascinating phenomenon! (Video and image credit: H. Watanabe et al.; research credit: H. Watanabe et al. and K. Kobayashi et al.)

Jets From Impact

When a test tube of liquid hits a surface, the curvature of the meniscus focuses the rebounding fluid into a jet. In this video, researchers show some of the many variations they’ve explored on these experiments–from changing the depth of the fluid and the shape of the container, to changing the working fluid to honey or to dry grains. It’s a nice introduction to a fascinating phenomenon! (Video and image credit: H. Watanabe et al.; research credit: H. Watanabe et al. and K. Kobayashi et al.)

Liquid Pulleys and Gears

In mechanical systems, gears and pulleys transmit rotation from one location to another. Here, researchers explore a fluid dynamical version of such systems. The set-up consists of two rotors contained in a cylindrical corral filled with a water-glycerin mixture. One of the rotors is active, marked here with orange; the other (blue) one is passive, meaning that it can rotate due to the forces on it but it is not actively driven by a motor.

The three flow visualizations illustrate different configurations the rotors can take on, depending on their separation distance. In the top image, the rotors have a moderate separation distance and the passive one rotates opposite of the active one. That rotation direction is set by the high-shear flow on its inner side. If the rotors are close together (left image), they rotate in the same direction, aided by strong shear on the outside edge of the passive rotor; this mimics being linked with a belt. And, finally, if the rotors are widely separated, they also corotate, with the fluid in between acting like a virtual gear linking them. (Image credit: J. Smith et al.)

Plucking Droplets

A sudden breeze can pluck droplets hanging from a stem. Here, researchers recreate that phenomenon in the laboratory. With a close-up view and high-speed images, we can enjoy every detail of the detachment and break-up. As the wire pulls away, it drags a liquid sheet off the droplet. The thicker rims on either side of the sheet eventually collide, creating a jet that stretches, deforms, and, at last, breaks. (Video and image credit: D. Maity et al.)

Bouncing on a Wave

On a vibrating fluid, droplets can bounce and interact in complex ways. Here, researchers demonstrate some of the peculiar dynamics of these wave-guided droplets, showing how they can do things like pair up in waltzes. To keep the droplets from coalescing with one another, they perform their experiments in a pressurized chamber; the higher air pressure makes it harder for the air film between droplets to drain during a collision, making the droplets unable to coalesce. Under these conditions, the authors show that the droplet-wave system has quantum-like statistics. (Video and image credit: J. Clampett et al.)

Bouncing on a Wave

On a vibrating fluid, droplets can bounce and interact in complex ways. Here, researchers demonstrate some of the peculiar dynamics of these wave-guided droplets, showing how they can do things like pair up in waltzes. To keep the droplets from coalescing with one another, they perform their experiments in a pressurized chamber; the higher air pressure makes it harder for the air film between droplets to drain during a collision, making the droplets unable to coalesce. Under these conditions, the authors show that the droplet-wave system has quantum-like statistics. (Video and image credit: J. Clampett et al.)

Bouncing on a Wave

On a vibrating fluid, droplets can bounce and interact in complex ways. Here, researchers demonstrate some of the peculiar dynamics of these wave-guided droplets, showing how they can do things like pair up in waltzes. To keep the droplets from coalescing with one another, they perform their experiments in a pressurized chamber; the higher air pressure makes it harder for the air film between droplets to drain during a collision, making the droplets unable to coalesce. Under these conditions, the authors show that the droplet-wave system has quantum-like statistics. (Video and image credit: J. Clampett et al.)

Bouncing on a Wave

On a vibrating fluid, droplets can bounce and interact in complex ways. Here, researchers demonstrate some of the peculiar dynamics of these wave-guided droplets, showing how they can do things like pair up in waltzes. To keep the droplets from coalescing with one another, they perform their experiments in a pressurized chamber; the higher air pressure makes it harder for the air film between droplets to drain during a collision, making the droplets unable to coalesce. Under these conditions, the authors show that the droplet-wave system has quantum-like statistics. (Video and image credit: J. Clampett et al.)

Bouncing on a Wave

On a vibrating fluid, droplets can bounce and interact in complex ways. Here, researchers demonstrate some of the peculiar dynamics of these wave-guided droplets, showing how they can do things like pair up in waltzes. To keep the droplets from coalescing with one another, they perform their experiments in a pressurized chamber; the higher air pressure makes it harder for the air film between droplets to drain during a collision, making the droplets unable to coalesce. Under these conditions, the authors show that the droplet-wave system has quantum-like statistics. (Video and image credit: J. Clampett et al.)

“Sidewall Symphony”

Flow visualization is both an art and science in fluid dynamics. Here, researchers were interested in studying the separation bubble that forms over a backward-facing ramp–a shape that shows up, for example, on an aircraft. In these areas, the flow over the surface separates, leaving an unsteady, recirculating bubble.

That’s the flow that researchers are visualizing here. They’ve done so by adding tiny helium-filled soap bubbles to the flow. With bright lights illuminating the bubbles, each one leaves a streak in a photograph, showing where the bubble moved during the time the camera’s shutter was open. Although images like these are beautiful, they can also be analyzed by computers to extract the underlying flow that created the image. (Image and research credit: B. Steinfurth et al.; see also here)

Schooling at Scale

Relatively simple visual and hydrodynamic signals are enough to make digital fish school in ways that resemble living ones. Here, researchers look at what happens when well-behaved schools of fish get too big. The researchers first demonstrate that their schools behave reasonably at one hundred members, either in a schooling configuration or a group milling around a central region.

At one thousand fish, the schools are still reasonably coherent and sensible. But at fifty thousand fish, the picture is drastically different. Neither schooling nor milling groups are able to remain together. They fracture and scatter into smaller groupings. (Video and image credit: H. Hang et al.)

Bursting an Oobleck Bubble

When soap bubbles burst, the hole grows as an expanding circle. But not every fluid bursts this same way. Here, researchers let air rise through oobleck–a fluid made from cornstarch suspended in water–to form a bubble. In time, as with all bubbles, the oobleck bubble bursts. But–in keeping with oobleck’s solid-like properties–the film tears open and fractures. As it sinks back into the liquid, it wrinkles before it slowly relaxes back into fluid form. (Video and image credit: X. Zhang et al.)

Bursting Bubbles

When air bubbles rise through a liquid, they scavenge dust, viruses, microplastics, and other impurities as they go. Once at the surface, these contaminant-covered bubbles thin and burst, generating many tiny droplets that arc through the air above. You’re likely familiar with the sight and sensation from a glass of champagne or soda.

Here, researchers have stacked two sets of sequential images to illustrate this complicated flowscape. Under the surface, a trio of photos are stacked to show bubbles rising and gathering at the surface. In the air, the researchers have stacked thirty sequential images, which together trace out the parabolic arcs of droplets sprayed by the bursting bubbles. (Image credit: J. Do and B. Wang)

Bioconvection

Convection isn’t always driven by temperature. Here, researchers explore the convective patterns formed by Thiovulum bacteria. These bacteria are negatively buoyant, meaning they will sink if they aren’t swimming. They also have an asymmetric moment of inertia, so any flow moving past them tends to affect their swimming direction.

When let loose in a Hele-Shaw cell with a oxygen levels that decrease with depth, the bacteria create complex convection-like patterns. They swim slowly upward in wide, slow plumes and sink in denser, narrow plumes. In other areas, they form large-scale rotating vortices. (Video and image credit: O. Kodio et al.)

Inside Cepheid Variable Stars

Cepheid variable stars pulsate in brightness over regular periods. That’s one reason astronomers use them as a standard candle to judge distances–even for stars well outside our galaxy. In this image, researchers display a simulation of convection inside a Cepheid eight times more massive than our sun. The colors represent vorticity, with zero vorticity in white.(Image credit: M. Stuck and J. Pratt)

“Broken Water, Like Broken Glass”

How can you break water? By accelerating it so quickly that the pressure drop forms cavitation bubbles. Here, a steel piston rests against a transparent plate, all underwater. When a hammer strike accelerates the piston away at around 1000g, the severe pressure drop tears the water into bubbles (bottom, left). As the bubbles expand, the nearby piston squishes them into pancakes (bottom, center). As they continue growing, the bubbles press into one another, squeezing thin ridges of water between them. The result (center) resembles broken glass. (Image credit: J. da Silva et al.)

A Bubbly Heart

Next time you fill your water bottle, watch closely and see if you can spot a bubble heart like these. When a jet falls into a pool, it pulls air in with it. The low pressure of the jet pulls bubbles inward, even as shear pulls the bubbles downward with the sinking liquid. If the bubbles are large and there’s enough momentum in the jet, the lower portion of the bubble will get pulled into a conical shape, while the upper portion remains a hemisphere. That forms one lobe of the heart. The other half requires a second bubble. But with a little patience and luck, you can form a complete heart. Happy Valentine’s Day! (Image credit: S. Tuley et al.)

Jupiter in a Lab

The vivid bands of a gas giant like Jupiter come from the planet’s combination of rotation and convection. It’s possible to create the same effect in a lab by rapidly spinning a tank of water around a central ice core. That’s the physical set-up behind this research poster–note the illustration in the lower right corner. The central snapshots show how temperature gradients on the water surface change the faster the tank rotates. At higher rotational speeds, the parabolic water surface gets ever steeper and Jupiter-like temperature bands form. (Image credit: C. David et al.)

Flow Through Granular Beds

We often rely on water draining through beds of grains, whether it’s the soil foundation beneath a building or the sand-and-gravel-filter used in water treatment. But how does water move through these tortuous porous passages? That’s what we see in this video, which places grains in a jig resembling an ant farm and lets us watch as water–and air–drain through the grains. The result is more complicated than you might imagine, with dry pockets, weak spots, and developing sinkholes. (Video and image credit: J. Choi et al.)

Inside a Bubble’s Burst

When bubbles burst at an interface, both their exterior and interior get spread into the air. Here, researchers watch as a fog-filled bubble rises through silicone oil and settles as the surface. Instabilities ripple down the bubble’s cap as it thins, and, once the bubble bursts, the fog from within is pushed upward, curling into a vortex as it goes. (Video and image credit: R. Shabtay and I. Jacobi; via GFM)

Wavy Water Entry

When an object like a sphere enters the water, it drags air into the water behind it, creating a cavity. Depending on the sphere’s impact speed, the cavity might close first under the water, forming a deep seal, or at the surface with a surface seal. But, as this video points out, water often isn’t still. Here, they explore how the sphere’s entry changes when there are ripples on the water surface. (Video and image credit: M. Ibrahim et al.; via GFM)

ExaWind Simulation

Large-scale computational fluid dynamics simulations face many challenges. Among them is the need to capture both large physical scales–like those of Earth’s atmospheric boundary layer–and small scales–like those of tiny eddies moving around a wind-turbine blade. Capturing all of these scales for a problem like four wind turbines in a wind farm requires using the full computing power of every processor in a large supercomputer. That’s the level of power behind the simulation visualized in this video. The results, however, are stunning. (Video and image credit: M. da Frahan et al.)

Superwalking Droplets

When placed on a vibrating oil bath, droplets have many wild behaviors, some of which mirror quantum mechanics. Even big droplets — bigger than 2 millimeters in diameter — can get in on the fun. This video shows several of these “jumbo superwalkers” in action, both singly and in groups. (Video and image credit: Y. Li and R. Valani; via GFM)

Event-Based Recording

High-speed cameras are an amazing tool in fluid dynamics, but they come with a whole host of challenges. The camera and lighting have to be positioned to deal with reflections, the data sets are enormous, and post-processing all that data takes a long time.

Here, researchers experiment instead with studying a flow using an event-based camera, which records information only when and where the brightness changes. The images and videos look strange to our eyes, but, as the authors show, they work nicely for identifying flow features and extracting valuable data. (Video and image credit: D. Sun et al.)

Droplets Through a Forest

When droplets flow through a forest of microfluidic posts, they can deform around the obstacle or break up into smaller droplets. Here, researchers explore the factors that control the outcome, as well as when droplets collide, coalesce, and mix. (Video and image credit: D. Meer et al.)

Leaves Dance in the Wind

Once a breeze kicks up, leaves on a tree start dancing. Every tree’s leaves have their own shapes, some of which appear very different from other trees. But their dances have patterns, as this video shows. In it, researchers explore how leaves of different shapes deform in the wind and how they can decompose that motion to compare across leaves. (Video and image credit: K. Mulleners et al.; via GFM)