#droplets — Public Fediverse posts

Representing Rain’s Microphysics

Realistically modeling rainfall remains an extremely difficult problem. To be practical, results have to be on the scale of kilometers; no one is looking to find out whether rain will fall from one specific cloud over their head. But making that prediction depends on physics that happens at the microscale, where droplets tens of microns in size are condensing, colliding, and eventually growing large enough to fall as rain. A new study takes a look at three machine-learning models that could help describe those microscale physics with less computational overhead.

The researchers used three different algorithms, all trained on high-quality simulations of microdroplet physics. The goal here was to represent the complex, nonlinear physics reflected in those results with an algorithm that’s less complicated and less computationally expensive than the methods used to create the training data. The team then tested the trained algorithms to see how they performed in conditions that were different than their training data.

They found that the model with the best performance–in terms of giving more accurate predictions in the test cases–was actually the simplest of the three models. So it may be possible to get reasonable results for rain microphysics from simpler, easier-to-compute algorithms. The team does warn, though, that all of the models need more work before they’d be ready to add to commercial-grade weather prediction software. (Image credit: J. Fowler; research credit: E. de Jong et al.; via Eos)

Capillary Slinkies

Nature is full of helical fibers, including in plants and bird feathers. In this study, researchers explore how these soft springs react to droplets. When the pitch of the spring (roughly speaking, the spacing between coils) is small, droplets can flow down in a plug (not shown). But as the pitch increases, droplets can take on a caterpillar-like (or, eruciform) shape. These drops descend quickly, in part, the team found, because internal flows within the droplet help it along.

Other drops maintain a spherical shape as they descend the widely-spaced coils of the spring. These drops tend to spin around the coil as they go, with their center of mass actually moving side-to-side as they descend. (Image and research credit: B. Bhatt and A. Carlson)

One of my favourite photos from the past when word was a simpler place (or at least I thought so)

#Photography #Nature #Droplets #MacroPhotography #NaturePhotography #BlueSkyArtShow #Water

Droplets Can Climb Sugar Fibers

In nature, droplets and fibers can meet on a spider’s web, on fur, or on a dew-gathering cactus. Here, researchers explore what happens when the droplet can dissolve the fiber it’s suspended on. As the authors note, a lumberjack who cuts the branch they sit on makes a fatal choice. The droplet sees a different outcome.

As the droplet hangs on the fiber, it dissolves the fiber’s sugar. Dense, sugar-laden water flows downward along the fiber and a replenishing upward flow goes along the droplet’s exterior. Because the sugar concentration is lower near the top of the drop, the fiber thins most quickly there.

The droplet has capillary forces along its top and bottom, where it meets the fiber. At the top, the droplet is free to expand, wetting more fiber, but the bottom of the drop is pinned to the fiber. The excess capillary force there goes into compressing the fiber.

As soon as the fiber breaks, the capillary force is no longer balanced, and the droplet jumps upward. If the drop and fiber are sized just right, the drop will jump upward enough to stay attached to the fiber instead of falling off. (Image and research credit: S. Dorbolo et al.)

I don't know if I go to the woods to take pictures, or if I take pictures to have a reason to go to the woods. An ADHD mind can be strange sometimes. Yesterday I arrived at the river just as it started to rain. I waded into the water, walking along the bank, and after a while the rain stopped. The sun came out, and I was able to take pictures of the raindrops on the willow growing by the bank. The white willow has a unique shade of green.
#nature #naturephotography #macro #droplets

A drop of water is never just a drop.

#LeidenLog #Droplets #Physics #SurfaceScience #FluidDynamics #LeidenfrostEffect

#Dew-Kissed #Yellow #Gerbera #Daisies by Kaye Menner #Photography Wide variety #Prints & lovely #Products at:

https://buff.ly/4WQobDc

#flowers #floral #droplets #yellowblack #homedecor #mastoart #fediverse #fediart #fedigiftshop #giftideas #wallartforsale #Art #artforsale #BuyIntoArt #AYearForArt #Artist #FineArtAmerica #PhotographyFeed #VisualArts #CreativeArts

Droplets in dense sprays live much longer than expected. The surrounding vapor saturates locally, delaying evaporation.

What controls the system is not the droplet, but the evolving vapor field.

🔗 https://journals.aps.org/prfluids/abstract/10.1103/ms1r-7jb9

#PhaseChange #Evaporation #Turbulence #Droplets #Physics

What makes an evaporating droplet suddenly break apart?

This study links vapor bubble growth and collapse to different atomization regimes in microemulsion droplets, revealing how interfacial instabilities drive fragmentation.

🔗 https://doi.org/10.1103/prbb-cbyr

#FluidDynamics #Droplets #Atomization #MultiphaseFlow #physics