#rotatingflow — Public Fediverse posts

Recreating Atmospheres

In planetary atmospheres, energy and vorticity can cascade from large scales to smaller ones, but the mechanics of this transfer remain somewhat elusive. In a recent experiment, researchers built a lab-scale representation of an atmosphere using a meter-scale rotating annular tank. The outer bottom edge of the tank gets heated–representing the sun’s warming at the equator–while a pipe in the center of the tank gets cooled near the tank surface, which mimics the chilling effect of the poles. Researchers filled the tank with a water-glycerol mixture and recorded how their artificial atmosphere responded at different rotation rates.

The results show an energy spectrum that’s consistent with atmospheric observations–with a steep drop at large length scales and a flatter one at smaller scales. But interestingly, they also found that the cascade was temperature-dependent in ways that current models don’t predict. Untangling that effect could help us understand not only our atmosphere but those of other planets. (Image credit: tank – H. Scolan, animation – S. Ding et al.; research credit: S. Ding et al.; via APS)

Recreating Atmospheres

In planetary atmospheres, energy and vorticity can cascade from large scales to smaller ones, but the mechanics of this transfer remain somewhat elusive. In a recent experiment, researchers built a lab-scale representation of an atmosphere using a meter-scale rotating annular tank. The outer bottom edge of the tank gets heated–representing the sun’s warming at the equator–while a pipe in the center of the tank gets cooled near the tank surface, which mimics the chilling effect of the poles. Researchers filled the tank with a water-glycerol mixture and recorded how their artificial atmosphere responded at different rotation rates.

The results show an energy spectrum that’s consistent with atmospheric observations–with a steep drop at large length scales and a flatter one at smaller scales. But interestingly, they also found that the cascade was temperature-dependent in ways that current models don’t predict. Untangling that effect could help us understand not only our atmosphere but those of other planets. (Image credit: tank – H. Scolan, animation – S. Ding et al.; research credit: S. Ding et al.; via APS)

Recreating Atmospheres

In planetary atmospheres, energy and vorticity can cascade from large scales to smaller ones, but the mechanics of this transfer remain somewhat elusive. In a recent experiment, researchers built a lab-scale representation of an atmosphere using a meter-scale rotating annular tank. The outer bottom edge of the tank gets heated–representing the sun’s warming at the equator–while a pipe in the center of the tank gets cooled near the tank surface, which mimics the chilling effect of the poles. Researchers filled the tank with a water-glycerol mixture and recorded how their artificial atmosphere responded at different rotation rates.

The results show an energy spectrum that’s consistent with atmospheric observations–with a steep drop at large length scales and a flatter one at smaller scales. But interestingly, they also found that the cascade was temperature-dependent in ways that current models don’t predict. Untangling that effect could help us understand not only our atmosphere but those of other planets. (Image credit: tank – H. Scolan, animation – S. Ding et al.; research credit: S. Ding et al.; via APS)

Recreating Atmospheres

In planetary atmospheres, energy and vorticity can cascade from large scales to smaller ones, but the mechanics of this transfer remain somewhat elusive. In a recent experiment, researchers built a lab-scale representation of an atmosphere using a meter-scale rotating annular tank. The outer bottom edge of the tank gets heated–representing the sun’s warming at the equator–while a pipe in the center of the tank gets cooled near the tank surface, which mimics the chilling effect of the poles. Researchers filled the tank with a water-glycerol mixture and recorded how their artificial atmosphere responded at different rotation rates.

The results show an energy spectrum that’s consistent with atmospheric observations–with a steep drop at large length scales and a flatter one at smaller scales. But interestingly, they also found that the cascade was temperature-dependent in ways that current models don’t predict. Untangling that effect could help us understand not only our atmosphere but those of other planets. (Image credit: tank – H. Scolan, animation – S. Ding et al.; research credit: S. Ding et al.; via APS)

Recreating Atmospheres

In planetary atmospheres, energy and vorticity can cascade from large scales to smaller ones, but the mechanics of this transfer remain somewhat elusive. In a recent experiment, researchers built a lab-scale representation of an atmosphere using a meter-scale rotating annular tank. The outer bottom edge of the tank gets heated–representing the sun’s warming at the equator–while a pipe in the center of the tank gets cooled near the tank surface, which mimics the chilling effect of the poles. Researchers filled the tank with a water-glycerol mixture and recorded how their artificial atmosphere responded at different rotation rates.

The results show an energy spectrum that’s consistent with atmospheric observations–with a steep drop at large length scales and a flatter one at smaller scales. But interestingly, they also found that the cascade was temperature-dependent in ways that current models don’t predict. Untangling that effect could help us understand not only our atmosphere but those of other planets. (Image credit: tank – H. Scolan, animation – S. Ding et al.; research credit: S. Ding et al.; via APS)

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.)

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.)

Competing Time Scales

Fluid dynamics often comes down to a competition between the different forces acting in a flow. Inertia, surface tension, viscosity, gravity, rotation — flows can be affected by all of these and more. In this video, researchers describe the three dominant forces in a rotating fluid like a planet’s atmosphere: viscosity, the fluid’s resistance to flowing; inertia, the fluid’s resistance to accelerating; and rotation, the overall spin of a fluid.

As shown in the video, which of these three forces dominates will change depending on the speed at which the force acts. We quantify this concept using time scales; the force with the smallest time scale can act fastest and will, therefore, win the tug-of-war. (Video and image credit: UCLA SpinLab)

#DIYFluids #flowVisualization #fluidDynamics #inertia #mathematics #physics #rotatingFlow #science #viscosity

Competing Time Scales

Fluid dynamics often comes down to a competition between the different forces acting in a flow. Inertia, surface tension, viscosity, gravity, rotation — flows can be affected by all of these and more. In this video, researchers describe the three dominant forces in a rotating fluid like a planet’s atmosphere: viscosity, the fluid’s resistance to flowing; inertia, the fluid’s resistance to accelerating; and rotation, the overall spin of a fluid.

As shown in the video, which of these three forces dominates will change depending on the speed at which the force acts. We quantify this concept using time scales; the force with the smallest time scale can act fastest and will, therefore, win the tug-of-war. (Video and image credit: UCLA SpinLab)

#DIYFluids #flowVisualization #fluidDynamics #inertia #mathematics #physics #rotatingFlow #science #viscosity

Competing Time Scales

Fluid dynamics often comes down to a competition between the different forces acting in a flow. Inertia, surface tension, viscosity, gravity, rotation — flows can be affected by all of these and more. In this video, researchers describe the three dominant forces in a rotating fluid like a planet’s atmosphere: viscosity, the fluid’s resistance to flowing; inertia, the fluid’s resistance to accelerating; and rotation, the overall spin of a fluid.

As shown in the video, which of these three forces dominates will change depending on the speed at which the force acts. We quantify this concept using time scales; the force with the smallest time scale can act fastest and will, therefore, win the tug-of-war. (Video and image credit: UCLA SpinLab)

#DIYFluids #flowVisualization #fluidDynamics #inertia #mathematics #physics #rotatingFlow #science #viscosity

Competing Time Scales

Fluid dynamics often comes down to a competition between the different forces acting in a flow. Inertia, surface tension, viscosity, gravity, rotation — flows can be affected by all of these and more. In this video, researchers describe the three dominant forces in a rotating fluid like a planet’s atmosphere: viscosity, the fluid’s resistance to flowing; inertia, the fluid’s resistance to accelerating; and rotation, the overall spin of a fluid.

As shown in the video, which of these three forces dominates will change depending on the speed at which the force acts. We quantify this concept using time scales; the force with the smallest time scale can act fastest and will, therefore, win the tug-of-war. (Video and image credit: UCLA SpinLab)

#DIYFluids #flowVisualization #fluidDynamics #inertia #mathematics #physics #rotatingFlow #science #viscosity

Competing Time Scales

Fluid dynamics often comes down to a competition between the different forces acting in a flow. Inertia, surface tension, viscosity, gravity, rotation — flows can be affected by all of these and more. In this video, researchers describe the three dominant forces in a rotating fluid like a planet’s atmosphere: viscosity, the fluid’s resistance to flowing; inertia, the fluid’s resistance to accelerating; and rotation, the overall spin of a fluid.

As shown in the video, which of these three forces dominates will change depending on the speed at which the force acts. We quantify this concept using time scales; the force with the smallest time scale can act fastest and will, therefore, win the tug-of-war. (Video and image credit: UCLA SpinLab)

#DIYFluids #flowVisualization #fluidDynamics #inertia #mathematics #physics #rotatingFlow #science #viscosity

Spinning Water

If you spin a tank of water at a constant speed, it takes on a curved, parabolic shape–a demonstration often called Newton’s bucket. Here, a team from UCLA shows how it’s done, both in terms of the equipment needed and a concise explanation of the physics. In the rotating experiment, water is subjected to both gravity (which acts in a constant magnitude across the tank) and centrifugal force (which is stronger further from the axis of rotation). The shape that balances these forces is a paraboloid, which is why the water takes on that shape. (Video and image credit: UCLA SpinLab)

#centrifugalForce #DIYFluids #fluidDynamics #physics #rotatingFlow #science

Bubbly Tornadoes Aspin

Rotating flows are full of delightful surprises. Here, the folks at the UCLA SpinLab demonstrate the power a little buoyancy has to liven up a flow. Their backdrop is a spinning tank of water; it’s been spinning long enough that it’s in what’s known as solid body rotation, meaning that the water in the tank moves as if it’s one big spinning object. To demonstrate this, they drop some plastic tracers into the water. These just drop to the floor of the tank without fluttering, showing that there’s no swirling going on in the tank. Then they add Alka-Seltzer tablets.

As the tablets dissolve, they release a stream of bubbles, which, thank to buoyancy, rise. As the bubbles rise, they drag the surrounding water with them. That motion, in turn, pulls water in from the surroundings to replace what’s moving upward. That incoming water has trace amounts of vorticity (largely due to the influence of friction near the tank’s bottom). As that vorticity moves inward, it speeds up to conserve angular momentum. This is, as the video notes, the same as a figure skater’s spin speeding up when she pulls in her arms. The result: a beautiful, spiraling bubble-filled vortex. (Video and image credit: UCLA SpinLab)

#buoyancy #conservationOfAngularMomentum #flowVisualization #fluidDynamics #physics #rotatingFlow #science

The Best of FYFD 2024

Welcome to another year and another look back at FYFD’s most popular posts. (You can find previous editions, too, for 2023, 2022, 2021, 2020, 2019, 2018, 2017, 2016, 2015, and 2014. Whew, that’s a lot!) Here are some of 2024’s most popular topics:

• The Taum Sauk Dam Failure and Its Legacy
• Stretching Ant Rafts
• Gigapixel Supernova
• Feynman’s Sprinkler Solved
• Calming the Waves
• “Dew Point” Deposits Droplets
• Drying Unaffected by Humidity
• Trapped in a Taylor Column
• Exciting a Flame in a Trough
• Remembering Rivers Past
• A Comet’s Tail
• Light Pillars
• Liquid Metal Printing
• The Miscible Faraday Instability
• A Triangular Prominence

This year’s topics are a good mix: fundamental research, civil engineering applications, geophysics, astrophysics, art, and one good old-fashioned brain teaser. Interested in what 2025 will hold? There are lots of ways to follow along so that you don’t miss a post.

And if you enjoy FYFD, please remember that it’s a reader-supported website. I don’t run ads, and it’s been years since my last sponsored post. You can help support the site by becoming a patron, buying some merch, or simply by sharing on social media. And if you find yourself struggling to remember to check the website, remember you can get FYFD in your inbox every two weeks with our newsletter. Happy New Year!

(Image credits: dam – Practical Engineering, ants – C. Chen et al., supernova – NOIRLab, sprinkler – K. Wang et al., wave tank – L-P. Euvé et al., “Dew Point” – L. Clark, paint – M. Huisman et al., iceberg – D. Fox, flame trough – S. Mould, sign – B. Willen, comet – S. Li, light pillars – N. Liao, chair – MIT News, Faraday instability – G. Louis et al., prominence – A. Vanoni)

#admin #ants #astrophysics #civilEngineering #comet #damFailure #drying #flowVisualization #fluidDynamics #fluidsAsArt #FYFD #instability #physics #plasma #rivers #rotatingFlow #science #selfExcitedOscillation #TaylorColumn #waveInterference

How Magnetic Fields Shape Core Flows

The Earth’s inner core is a hot, solid iron-rich alloy surrounded by a cooler, liquid outer core. The convection and rotation in this outer core creates our magnetic fields, but those magnetic fields can, in turn, affect the liquid metal flowing inside the Earth. Most of our models for these planetary flows are simplified — dropping this feedback where the flow-induced magnetic field affects the flow.

The simplification used, the Taylor-Proudman theorem, assumes that in a rotating flow, the flow won’t cross certain boundaries. (To see this in action, check out this Taylor column video.) The trouble is, our measurements of the Earth’s actual interior flows don’t obey the theorem. Instead, they show flows crossing that imaginary boundary.

To explore this problem, researchers built a “Little Earth Experiment” that placed a rotating tank (representing the Earth’s inner and outer core) filled with a transparent, magnetically-active fluid inside a giant magnetic. This setup allowed researchers to demonstrate that, in planetary-like flows, the magnetic field can create flow across the Taylor-Proudman boundary. (Image credit: C. Finley et al.; research credit: A. Pothérat et al.; via APS Physics)

#fluidDynamics #magnetohydrodynamics #physics #planetaryScience #rotatingFlow #science #TaylorColumn #TaylorProudmanTheorem