#granularmaterial — Public Fediverse posts

Seeing Stress in an Avalanche

Researchers sometimes study avalanches and other granular flows in a rolling drum, where grains can cascade down continuously. Here, the twist is that they’ve done it with photoelastic disks, which show stress patterns when viewed under crossed polarizing filters.

In any given moment, the contacts between neighboring particles form a force chain that lights up the disks. In motion, the effect resembles lightning forking and branching across the sky. The close-ups of stress reverberating during impact are especially mesmerizing. (Video and image credit: R. Hodgson 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.)

Waves Over Sand Ripples

Look beneath the waves on a beach or in a bay, and you’ll find ripples in the sand. Passing waves shape these sandforms and can even build them to heights that require dredging to keep waterways passable to large ships. To better understand how the sand interacts with the flow, researchers build computer models that couple the flow of the water with the behavior of individual sand grains. One recent study found that sand grains experienced the most shear stress as the flow first accelerates and then again when a vortex forms near the crest of the ripple. (Image credit: D. Hall; research credit: S. DeVoe et al.; via Eos)

#CFD #computationalFluidDynamics #fluidDynamics #geophysics #granularMaterial #oceanWaves #physics #sandRipples #science #sedimentTransport #sedimentation

“Dispersion”

In “Dispersion,” particles spread under the influence of an unseen fluid. Like Roman de Giuli’s work, filmmaker Susi Sie creates macro images that look like ice floes, deserts, and river deltas viewed from above. This similarity of patterns at both large and small scales is a specialty of fluid physics. Just as artists use it to mimic larger flows, scientists use it to study planet-scale problems in the lab. (Video and image credit: S. Sie et al.)

#dispersion #fluidDynamics #fluidsAsArt #granularFlow #granularMaterial #particulates #physics #reynoldsSimilarity #science

Thawing Permafrost Primes Slumps

As permafrost thaws on Arctic hillsides and shorelines, the land often deforms in a unique fashion, known as a slump. Formally known as mega retrogressive thaw slumps, these areas superficially resemble a landslide. They’re also prone to repeat performances: as many as 90% of Canada’s Arctic slumps recur in the same place as previous slumps. Researchers used ground-penetrating radar and other tools to study the underground structure at slumps and found that several factors contribute to this repetitive cycle.

Seawater soaking into the foot of a hilly shore can destabilize the permafrost, creating a slump. That changes the nearby ground cover, exposing more permafrost to warming; their measurements showed this warming could extend tens of meters underground, priming the area for future slumps. Similarly, the mudslides and narrow ravines that form on an active slump also shift away ground cover and warm the underlying permafrost. Together, these factors suggest that once a slump forms, more slumps will occur as the underlying permafrost warms. (Image credit: M. Krautblatter; research credit: M. Krautblatter et al.; via Eos)

#erosion #fluidDynamics #geophysics #granularMaterial #physics #science #slump

Thawing Permafrost Primes Slumps

As permafrost thaws on Arctic hillsides and shorelines, the land often deforms in a unique fashion, known as a slump. Formally known as mega retrogressive thaw slumps, these areas superficially resemble a landslide. They’re also prone to repeat performances: as many as 90% of Canada’s Arctic slumps recur in the same place as previous slumps. Researchers used ground-penetrating radar and other tools to study the underground structure at slumps and found that several factors contribute to this repetitive cycle.

Seawater soaking into the foot of a hilly shore can destabilize the permafrost, creating a slump. That changes the nearby ground cover, exposing more permafrost to warming; their measurements showed this warming could extend tens of meters underground, priming the area for future slumps. Similarly, the mudslides and narrow ravines that form on an active slump also shift away ground cover and warm the underlying permafrost. Together, these factors suggest that once a slump forms, more slumps will occur as the underlying permafrost warms. (Image credit: M. Krautblatter; research credit: M. Krautblatter et al.; via Eos)

#erosion #fluidDynamics #geophysics #granularMaterial #physics #science #slump

Thawing Permafrost Primes Slumps

As permafrost thaws on Arctic hillsides and shorelines, the land often deforms in a unique fashion, known as a slump. Formally known as mega retrogressive thaw slumps, these areas superficially resemble a landslide. They’re also prone to repeat performances: as many as 90% of Canada’s Arctic slumps recur in the same place as previous slumps. Researchers used ground-penetrating radar and other tools to study the underground structure at slumps and found that several factors contribute to this repetitive cycle.

Seawater soaking into the foot of a hilly shore can destabilize the permafrost, creating a slump. That changes the nearby ground cover, exposing more permafrost to warming; their measurements showed this warming could extend tens of meters underground, priming the area for future slumps. Similarly, the mudslides and narrow ravines that form on an active slump also shift away ground cover and warm the underlying permafrost. Together, these factors suggest that once a slump forms, more slumps will occur as the underlying permafrost warms. (Image credit: M. Krautblatter; research credit: M. Krautblatter et al.; via Eos)

#erosion #fluidDynamics #geophysics #granularMaterial #physics #science #slump

“There is a crack in everything…”

When millimeter-sized drops of water infused with nanoparticles dry, they leave behind complex and beautiful residues. As water continues evaporating, the residues warp, bend, and crack. In this video, researchers set their science to the music of Leonard Cohen. The results resemble blooming flowers and flying water fowl. If you’d like to learn more about the science behind the art, check out the two open-access papers linked below. (Video and image credit: P. Lilin and I. Bischofberger; submitted by Irmgard B.; see also P. Lilin and I. Bischofberger and P. Lilin et al.)

#coffeeRings #cracking #droplets #drying #evaporation #fluidDynamics #fluidsAsArt #granularMaterial #particleSuspension #physics #science