# gst: scanning inside a granular raft

<< Rheology of macroscopic particle-laden interfaces, called “granular rafts,” has been experimentally studied in the simple shear configuration.  >>️

<< Close to the walls of the rheometer cell, one can observe regions of large local shear rate while in the middle of the cell a quasistatic zone exists. >>

<< Measuring the probability density functions of the instantaneous local shear rate, (AA) provide evidence of a balance between positive and negative instantaneous local shear rate. This behavior is the signature of a quasistatic region inside the granular raft. >>️

️

J. Lalieu, A. Seguin, G. Gauthier. Rheology of granular rafts. Phys. Rev. E 107, 064901. June 29, 2023.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.107.064901

Also: Bavand Keshavarz, Michela Geri. Mandelbrot granular raft. Phys. Rev. Fluids 8, 110506. Nov 16, 2023.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.8.110506

Also: grain, particle, in https://www.inkgmr.net/kwrds.html 

Also: << l'invasiva scorribanda /

sull' oramai alla deriva lacerata randa. >>️ in: Schismi da vibrati di tangone. Notes. March 23, 2005. (quasi-stochastic poetry)

https://inkpi.blogspot.com/2005/03/1608b-schismi-da-vibrati-di-tangone.html

Keywords: gst, raft, particle, grain, granular raft, life

# gst: apropos of transitions, tsunami waves generated by granular collapses.

<< Tsunami waves induced by landslides are a threat to human activities and safety along coastal areas. In this paper, (AA) characterize experimentally the waves generated by the gravity-driven collapse of a dry granular column into water. Three nonlinear wave regimes are identified depending on the Froude number Fr_f based on the ratio of the velocity of the advancing granular front and the velocity of linear gravity waves in shallow water: transient bores for large Fr_f, solitary waves for intermediate values of Fr_f, and nonlinear transition waves at small Fr_f. >>️

Wladimir Sarlin, Cyprien Morize, et al. Nonlinear regimes of tsunami waves generated by a granular collapse.    

Journal of Fluid Mechanics, 919, R6. doi:10.1017/ jfm.2021.400. May 28, 2021. 

https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/abs/nonlinear-regimes-of-tsunami-waves-generated-by-a-granular-collapse/3F38B26548B891FA9AE8A4018FF992A4#

James Badham. The Science of tsunamis. University of California. Santa Barbara. Jun 21, 2021. 

https://www.sciencedaily.com/releases/2021/06/210621160524.htm

Froude number (Fr_f)

https://en.m.wikipedia.org/wiki/Froude_number

Also

keyword 'grain' in FonT

https://flashontrack.blogspot.com/search?q=grain

keyword 'grani' in Notes (quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=grani

keyword 'waves' in FonT

https://flashontrack.blogspot.com/search?q=waves

keyword 'onda' in Notes (quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=onda

# gst: apropos of transitions among granular entities, the behavior of silicone-coated sand mixtures (the 'magic sand')

<< Sand is a fascinating material. It can flow and be poured like a liquid, but retains many of the properties of solids, clogging pipes or forming sand dunes. (..) Grains interact via simple, Newtonian mechanics, but because so many particles are interacting at once, there is an emergent complexity of flow behavior that cannot yet be explained by simple equations. Scientists are thus not only looking for better theoretical models to explain granular behavior, but convenient "model systems" that can be handled and tuned in the lab to give insights into how the microscopic structure of granular materials gives rise to their macroscopic properties. >>️️

<< A team (..) has studied the properties of mixtures of silicone-coated "magic sand," a popular kids' toy, and normal sand. Silicone-coated sand particles were found to interact only with each other and not with other sand particles. The team discovered that adding silicone-coated sand beyond a certain threshold leads to an abrupt change in clustering and rigidity, a potential way to tune the flow of granular materials for industry.>>️

<< Using three independent methods involving sieving, measuring density and forming stable mounds of sand, they found that the mechanical properties of the mixture changes drastically when the fraction of magic sand to normal sand exceeds 20%. This agreed with findings from percolation theory, which governs how connections between particles span space without any breakages, letting the sand mixture behave in a significantly more solid-like way and bear its own weight. This behavior is known for polymer gels, and helps unify theoretical approaches applied to completely different materials. The team's mixtures also exhibits mechanical properties that can be easily modified. Importantly, the method provides a new, convenient, accurate and informative way to explore granular physics, >>️

️

'Magic sand' might help us understand the physics of granular matter. Tokyo Metropolitan University. Mar 08, 2021.

https://phys.org/news/2021-03-magic-sand-physics-granular.html

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Marie Tani, Honoka Fujio, Rei Kurita. Transition Behavior in Silicone-coated Sand Mixtures. Journal of the Physical Society of Japan. 90 (3): 033801. doi: 10.7566/ JPSJ.90.033801.

https://journals.jps.jp/doi/10.7566/JPSJ.90.033801

Also

keyword 'grain' in FonT

https://flashontrack.blogspot.com/search?q=grain

keyword 'sand' in FonT

https://flashontrack.blogspot.com/search?q=sand

keyword 'sand' in Notes (quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=sand

keyword 'sabbia' in Notes (quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=sabbia

keyword 'grani' in Notes (quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=grani

# gst: movers and shaker, the dynamics of granular matter

 << Granular materials are disordered systems often found in a far-from-equilibrium state. >> 

 << You can think of it like a beaker filled with loose sand, (..) At first there are big holes between the grains. So initially, it's easy for a grain to shift position by falling into an empty space. But as these spaces start to get smaller, it becomes less likely that a grain can fall through one. As the taps continue, it takes increasingly cooperative events to create the space necessary for more compaction. >> Stefan Boettcher. 

<< Previous research has shown a similar statistical pattern for the behavior of amorphous solids that don't form ordered crystals when moving from a liquid to a solid state, such as glass and many polymers. >> 

Carol Clark. Movers and shakers: New evidence for a unifying theory of granular materials. Emory University. Jan 08, 2021. 

https://phys.org/news/2021-01-movers-shakers-evidence-theory-granular.html   

Paula A. Gago, Stefan Boettcher. 

Universal features of annealing and aging in compaction of granular piles. 

PNAS. 117 (52) 33072-33076. doi: 10.1073/ pnas.2012757117. Dec 14, 2020. 

https://www.pnas.org/content/117/52/33072

# gst: how two chaotic systems can synchronize

<< For the first time the researchers were able to measure the fine grain process that leads from disorder to synchrony, discovering a new kind of synchronization between chaotic systems. They call this new phenomenon Topological Synchronization. >>

<< Chaotic systems, although unpredictable, still have a subtle global organization called strange attractor (..) Every chaotic system attracts its own unique strange attractor. By Topological Synchronization we mean that two strange attractors have the same organization and structures. At the beginning of the synchronization process, small areas on one strange attractor have the same structure of the other attractor, meaning that they are already synced to the other attractor. At the end of the process, all the areas of one strange attractor will have the structure of the other and complete Topological Synchronization has been reached. >> Nir Lahav.

Scientists reveal for first time the exact process by which chaotic systems synchronize. Bar-Ilan University. Jan 7, 2019.

https://m.phys.org/news/2019-01-scientists-reveal-exact-chaotic-synchronize.html

Nir Lahav, Irene Sendina-Nadal, et al.
Synchronization of chaotic systems: A microscopic description. Phys. Rev. E 98, 052204. Nov 6, 2018. doi: 10.1103/PhysRevE.98.052204

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.98.052204

# gst: chemical waves exhibit fascinating patterns

<< Waves are known in many very different forms; as water waves, light waves or sound waves. But here we are dealing with something quite different - chemical waves >>

<< Typically, one imagines a chemical reaction like this: from specific initial reactants one obtains specific final products. But it does not need to be as simple as that. Self-sustaining oscillations may occur, i.e. periodic changes between two different states >>

<< On a polycrystalline surface, there are then different regions in which the cyclical process occurs at different frequencies. It is precisely this effect that creates those fascinating wave patterns. When a chemical wave moves across the surface and passes from the edge of one grain of crystal to another, it speeds up or slows down, similar to light passing from the air to water.  This changes the complex spiral wave structures according to the particular orientation of the grain surface >>

Vienna University of Technology. Chemical waves guide to catalysts of the future. Feb 20, 2018.

https://m.phys.org/news/2018-02-chemical-catalysts-future.html

Yuri Suchorski, Martin Datler, et al. Visualizing catalyst heterogeneity by a multifrequential oscillating reaction. Nature Communication. 2018; 9 (600). doi: 10.1038/s41467-018-03007-3. Feb 9,  2018.

https://www.nature.com/articles/s41467-018-03007-3