# gst: apropos of breaking mechanisms, crack of a floating particle raft caused by waves.

<< When particles of a few tens of microns are spread on the surface of water, they aggregate under the action of capillary forces and form a thin floating membrane, a particle raft. >>

<< For a sufficiently strong wave amplitude, the raft breaks up progressively by developing cracks and producing fragments whose sizes decrease on a timescale long compared to the period of the wave. (AA)  characterize the breaking mechanisms.  >>️️

<< The visual appearance of the fragments distributed in size and surrounded by open water bears a notable resemblance to the floes produced by the fracturing of sea ice by waves in the polar oceans. Fragmentation concepts and morphological tools built for sea ice floes can be applied to (AA) macroscopic analog, on which the entire dynamic evolution is accessible. However, the mechanics of the two systems differ, as (AA) particle raft breaks due to the viscous stresses, whereas the sea ice fractures due to its bending by the waves. >>️

Louis Saddier, Ambre Palotai, et al. Breaking of a floating particle raft by water waves. Phys. Rev. Fluids 9, 094302. Sep 27, 2024.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.9.094302 

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

Also: 'break' in  https://flashontrack.blogspot.com/search?q=break

Also: 'raft' in  https://flashontrack.blogspot.com/search?q=raft

Also: 'zattera' (quasi-stochastic poetry) in  https://inkpi.blogspot.com/search?q=zattera  'randa' (quasi-stochastic poetry) in https://inkpi.blogspot.com/search?q=randa

Keywords: gst, crack, break, particle, raft, particle raft

# gst: compression and fracture of ordered and disordered droplet rafts

AA << simulate a two-dimensional array of droplets being compressed between two walls. The droplets are adhesive due to an attractive depletion force. As one wall moves toward the other, the droplet array is compressed and eventually induced to rearrange. The rearrangement occurs via a fracture, where depletion bonds are quickly broken between a subset of droplets. >>

<< For monodisperse, hexagonally ordered droplet arrays, this fracture is preceded by a maximum force exerted on the walls, which drops rapidly after the fracture occurs. >>

<< In small droplet arrays a fracture is a single well-defined event, but for larger droplet arrays, competing fractures can be observed. These are fractures nucleated nearly simultaneously in different locations. >>

AA << also study the compression of bidisperse droplet arrays. The addition of a second droplet size further disrupts fracture events, showing differences between ideal crystalline arrays, crystalline arrays with a small number of defects, and fully amorphous arrays. >>

️

Pablo Eduardo Illing, Jean-Christophe Ono-dit-Biot, et al. Compression and fracture of ordered and disordered droplet rafts. Phys. Rev. E 109, 014610. Jan 17, 2024.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.014610

Also: drop, defect, fracture, crack, in https://www.inkgmr.net/kwrds.html

Also:  raft   https://flashontrack.blogspot.com/search?q=raft  

zattera (quasi-stochastic poetry) https://inkpi.blogspot.com/2005/04/1864-onda-di-liberazione.html  

randa (quasi-stochastic poetry) https://inkpi.blogspot.com/search?q=randa

Keywords: gst, drop, droplet, raft, defect, fracture, crack

# behav: mechanics of fire ant rafts as an active self-healing membrane

<< The unique ability of fire ants to form a raft to survive flooding rain has enchanted biologists as well as researchers in other disciplines. (..) a three-dimensional aggregation of fire ants exhibits viscoelasticity with respect to external compression and shearing among numerous unusual mechanical properties. >>️

AA << study the ant raft in its natural form, i.e., composing no more than two layers. This allowed to focus on the cracks that are unique to membranes and see how their patterns are influenced by the fact that these ants are mobile and can self-repair the damage to keep their raft from disintegration. >>️

They << show that vertical and horizontal shaking can also prompt fire ants to aggregate.  (..)  the pull force expedites the alignment of fire ants, in analogy to the effect of an electric field on liquid crystal polymers. >>️

<< One major finding is that the raft can exhibit zero Poisson's ratio without resorting to specific geometry structures. This is enabled by the active recruitment of ants from the top layer to the bottom layer to keep the raft from disintegrating. >>️

️

Chung-Hao Chen, Ting-Heng Hsieh, et al. Formation and mechanics of fire ant rafts as an active self-healing membrane. Phys. Rev. E 109, 014607. Jan 9, 2024. 

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.014607

David Ehrenstein. Material Properties of Fire-Ant Rafts. Physics 17, s5. Jan 9. 2024. 

https://physics.aps.org/articles/v17/s5

Also:  raft   https://flashontrack.blogspot.com/search?q=raft  

zattera (quasi-stochastic poetry) https://inkpi.blogspot.com/2005/04/1864-onda-di-liberazione.html  

randa (quasi-stochastic poetry) https://inkpi.blogspot.com/search?q=randa

Also: behav, behavior, in  https://www.inkgmr.net/kwrds.html

Keywords behavior, behaviour, ant, raft, self-healing

# 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. >>️

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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