Listening for Pollinators

Can plants recognize the sound of their pollinators? That’s the question behind this recently presented acoustic research. As bees and other pollinators hover, land, and take-off, their bodies buzz in distinctive ways. Researchers recorded these subtle sounds from a Rhodanthidium sticticum bee and played them back to snapdragons, which rely on that insect. They found that the snapdragons responded with an increase in sugar and nectar volume; the plants even altered their gene expression governing sugar transport and nectar production. The researchers suspect that the plants evolved this strategy to attract their most efficient pollinators and thereby increase their own reproductive success. (Image credit: E. Wilcox; research credit: F. Barbero et al.; via PopSci)

#acoustics #biology #fluidDynamics #insects #physics #plants #pollination #science

🤓 Oh joy, another thrilling episode of "Let's Pretend We Understand Hilbert and Boltzmann" — because fluid dynamics and kinetic theory are obviously everyone's favorite cocktail party topics. 🍸🔬 Good luck keeping your eyes open through this math-induced coma! 😴💤
https://arxiv.org/abs/2503.01800 #HackerNews #FluidDynamics #KineticTheory #MathHumor #ScienceComedy #HackerNews #ngated
Hilbert's sixth problem: derivation of fluid equations via Boltzmann's kinetic theory

In this paper, we rigorously derive the fundamental PDEs of fluid mechanics, such as the compressible Euler and incompressible Navier-Stokes-Fourier equations, starting from the hard sphere particle systems undergoing elastic collisions. This resolves Hilbert's sixth problem, as it pertains to the program of deriving the fluid equations from Newton's laws by way of Boltzmann's kinetic theory. The proof relies on the derivation of Boltzmann's equation on 2D and 3D tori, which is an extension of our previous work (arXiv:2408.07818).

arXiv.org

Rolling Down Soft Surfaces

Place a rigid ball on a hard vertical surface, and it will free fall. Stick a liquid drop there, and it will slide down. But researchers discovered that with a soft sphere and a soft surface, it’s possible to roll down a vertical wall. The effect requires just the right level of squishiness for both the wall and sphere, but when conditions are right, the 1-millimeter radius sphere rolls (with a little slipping) down the wall.

Rolling requires torque, something that’s usually lacking on a vertical surface. But the team found that their soft spheres got the torque needed to roll from their asymmetric contact with the surface. More of the sphere contacted above its centerline than below it. The researchers compared the way the sphere contacted the surface to a crack opening (at the back of the sphere) and a crack closing (at the front of the sphere). That asymmetry creates just enough torque to roll the sphere slowly. The team hopes their discovery opens up new possibilities for soft robots to climb and descend vertical surfaces. (Image and research credit: S. Mitra et al.; via Gizmodo)

#adhesion #fluidDynamics #physics #science #slip #softMatter #solidMechanics

Seeing the Sun’s South Pole For the First Time

The ESA-led Solar Orbiter recently used a Venus flyby to lift itself out of the ecliptic — the equatorial plane of the Sun where Earth sits. This maneuver offers us the first-ever glimpse of the Sun’s south pole, a region that’s not visible from the ecliptic plane. A close-up view of plasma rising off the pole is shown above, and the video below has even more.

Solar Orbiter will get even better views of the Sun’s poles in the coming months, perfect for watching what goes on as the Sun’s 11-year-solar-cycle approaches its maximum. During this time, the Sun’s magnetic poles will flip their polarity; already Solar Orbiter’s instruments show that the south pole contains pockets of both positive and negative magnetic polarity — a messy state that’s likely a precursor to the big flip. (Image and video credit: ESA & NASA/Solar Orbiter/EUI Team, D. Berghmans (ROB) & ESA/Royal Observatory of Belgium; via Gizmodo)

https://www.youtube.com/watch?v=TU4DcDgaMM0

#fluidDynamics #magnetohydrodynamics #physics #plasma #science #solarDynamics #sun

“Now I See – The Collection Vol. 2”

In the next video of his current collection, Roman De Giuli takes us flying over liquid landscapes that look like our Earth in miniature. Many of them have the feeling of river deltas or glaciers. Sharp-eyed viewers will notice bubbles and flotsam in some of these streams. If you follow them, you can see how the flows vary — wiggling around islands, speeding up through constrictions and slowing down when the stream widens. It is, as always, a beautiful form of flow visualization. (Video and image credit: R. De Giuli)

#flowVisualization #fluidDynamics #fluidsAsArt #laminarFlow #physics #riverDelta #science

Predicting Yield

We’ve all experienced the frustration of ketchup refusing to leave the bottle or toothpaste that shoots out suddenly. These materials are yield stress fluids, which transition from solid-like behavior to liquid flow once the right amount of force is applied. A new study suggests that — despite their wide range of characteristics — these fluids share a universal relation: their yield transition (when they start to flow) depends on their characteristics when at rest. Interestingly, this relationship seems to hold not only for polymeric fluids like the one in the study but also nonpolymeric ones. (Image credit: haideyy; research credit: D. Keane et al.; via APS Physics)

#fluidDynamics #physics #rheology #science #yieldStressFluid

Vortex ring - Wikipedia
"discontinuity introduced by the Dirac delta function prevents the computation of the speed and the kinetic energy of a circular vortex line. It is however possible to estimate these quantities for a vortex ring having a finite small thicknes"
#fluiddynamics https://en.wikipedia.org/wiki/Vortex_ring#:~:text=discontinuity%20introduced%20by%20the%20Dirac%20delta%20function%20prevents%20the%20computation%20of%20the%20speed%20and%20the%20kinetic%20energy%20of%20a%20circular%20vortex%20line.%20It%20is%20however%20possible%20to%20estimate%20these%20quantities%20for%20a%20vortex%20ring%20having%20a%20finite%20small%20thickness
Vortex ring - Wikipedia

Evaporating Off Butterfly Scales

This award-winning macro video shows scattered water droplets evaporating off a butterfly‘s wing. At first glance, it’s hard to see any motion outside of the camera’s sweep, but if you focus on one drop at a time, you’ll see them shrinking. For most of their lifetime, these tiny drops are nearly spherical; that’s due to the hydrophobic, water-shedding nature of the wing. But as the drops get smaller and less spherical, you may notice how the drop distorts the scales it adheres to. Wherever the drop touches, the wing scales are pulled up, and, when the drop is gone, the scales settle back down. This is a subtle but neat demonstration of the water’s adhesive power. (Video and image credit: J. McClellan; via Nikon Small World in Motion)

Water droplets evaporate from the wing of a peacock butterfly.

#adhesion #biology #butterfly #evaporation #fluidDynamics #hydrophobic #physics #science #sessileDrop

Io’s Missing Magma Ocean

In the late 1970s, scientists conjectured that Io was likely a volcanic world, heated by tidal forces from Jupiter that squeeze it along its elliptical orbit. Only months later, images from Voyager 1’s flyby confirmed the moon’s volcanism. Magnetometer data from Galileo’s later flyby suggested that tidal heating had created a shallow magma ocean that powered the moon’s volcanic activity. But newly analyzed data from Juno’s flyby shows that Io doesn’t have a magma ocean after all.

The new flyby used radio transmission data to measure any little wobbles that Io caused by tugging Juno off its expected course. The team expected a magma ocean to cause plenty of distortions for the spacecraft, but the effect was much slighter than expected. Their conclusion? Io has no magma ocean lurking under its crust. The results don’t preclude a deeper magma ocean, but at what point do you distinguish a magma ocean from a body’s liquid core?

Instead, scientists are now exploring the possibility that Io’s magma shoots up from much smaller pockets of magma rather than one enormous, shared source. (Image credit: NASA/JPL/USGS; research credit: R. Park et al.; see also Quanta)

#fluidDynamics #geophysics #Io #magma #physics #planetaryScience #science #subsurfaceOceans #tidalHeating #volcano