Turbulence and Bioluminescence

If you’ve ever seen crashing waves glowing blue, you’ve been treated to bioluminescence. Although many creatures can bioluminesce, tiny dinoflagellates–a type of marine phytoplankton–are one of the easiest to spot. These microscopic organisms create a flash of light in response to viscous stresses. Their response to flow-induced stresses is so robust that they can be used to visualize stress fields.

In a new study, researchers explored how turbulence affects the dinoflagellate’s luminescence. They mathematically modeled the dinoflagellate as an elastic dumbbell that emitted light based on its extent and rate of deformation. Then they explored how this model dinoflagellate behaved in different types of turbulent flows. They found that the fluctuations and intermittency of turbulent flows both encouraged the radiant displays. (Image credit: T. McKinnon; research credit: P. Kumar and J. Picardo)

#biology #bioluminescence #flowVisualization #fluidDynamics #physics #phytoplankton #science #turbulence

Thunderstorms Make Trees Glow

Scientists have long hypothesized that the high electrical charge of thunderstorms could produce an opposite charge in the ground that would discharge from the forest canopy. But this phenomenon, known as a corona, had never been observed on actual trees. A new study, however, has observed this ghostly ultraviolet (UV) glow from the tips of sweetgum leaves and loblolly pine needles during thunderstorms.

Catching these coronae in action required a new kind of UV detector that was ultra-sensitive to the particular band of UV-light emitted by coronas, hot fires, or mercury lamps. Since the latter two weren’t present during the team’s field observations, they were able to conclude that the light they detected came from coronae.

The group observed that corona discharges were transient, jumping from leaf to leaf and branch to branch across the forest canopy. For any creature capable of detecting that glow by eye, it must be incredible to watch the treetops lit by their own ever-shifting auroras during every thunderstorm. (Image credit: W. Brune; research credit: P. McFarland et al.; via SciAm)

#biology #corona #electrohydrodynamics #flowVisualization #fluidDynamics #physics #plasma #science #thunderstorms

“Arctic Fox in Blizzard”

A blue arctic fox bears the wind and snow of a Norwegian blizzard in this image by photographer Klaus Hellmich. The wind is strong enough to move snowflakes several centimeters in the time the camera’s shutter is open. This leaves the image full of streaklines that reveal the paths taken by the wind and snow. This visualization technique is useful in the lab, too. (Image credit: K. Hellmich; via Colossal)

#flowVisualization #fluidDynamics #fluidsAsArt #physics #science #streaklines

Understanding Schlieren

Schlieren techniques are one of my favorite forms of flow visualization. They cleverly make the invisible visible through an optical set-up that’s sensitive to changes in density. They’re great–as seen in the examples here–for seeing local buoyant flows like the plumes that rise from a candle, or for making gases like carbon dioxide visible. They’re also excellent for visualizing shock waves.

In this video, physicist David Jackson explains how one particular flavor of schlieren–one using a spherical mirror–works. There are lots of other possible schlieren set-ups, too, though each one has its quirks. (Video and image credit: All Things Physics; submitted by David J.)

#DIYFluids #flowVisualization #fluidDynamics #physics #schlierenPhotography #science

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)

#2025gofm #astrophysics #CFD #computationalFluidDynamics #convection #flowVisualization #fluidDynamics #numericalSimulation #physics #science

“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.)

#2025gofm #cavitation #flowVisualization #fluidDynamics #physics #science

A Supernova in Motion

In 1604, astronomers first caught sight of Kepler’s Supernova Remnant, a massive explosion some 17,000 light-years away. Twenty-five years of observations from the Chandra X-ray Observatory went into making this timelapse, which shows the supernova remnant‘s material pushing into the surrounding gas and dust.

In its fastest regions, the supernova remnant is moving around 2% of the speed of light–some 22 million kilometers per hour. Slower parts of the remnant are moving at just 0.5% of light-speed. (Image credit: NASA/CXC/SAO/Pan-STARRS; via Gizmodo)

#astrophysics #compressibleFlow #flowVisualization #fluidDynamics #physics #science #shockwave #supernova #turbulence

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.)

#2025gofm #atmosphericScience #convection #flowVisualization #fluidDynamics #Jupiter #physics #planetaryScience #rotatingFlow #science #turbulence

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.)

#2025gofm #drainage #flowVisualization #fluidDynamics #granularMaterial #physics #porousFlow #science

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)

#2025gofm #bubbles #bursting #flowVisualization #fluidDynamics #instability #physics #science #vortex