# gst: apropos of bubble rearrangements, transition from slip to scraping as critical-like behavior in foam dynamics.

<< Jamming systems, including colloids, emulsions, foams, and biological tissues, undergo significant deformation during processes like material scraping or wound self-healing. To adequately spread a foam or cream over a surface, external force must be applied to artificially scrape it. Notably, the transition from slip to scraping when foam is manipulated using a rigid plate remains poorly understood. >>

<< Systematic observations of the internal foam structure during scraping were conducted, and the scraping length was qualitatively analyzed by varying the scraping velocity. (AA) study reveals that the transition from slip to scraping is driven by the sequential propagation of bubble rearrangements. Furthermore, the scraping length diverges towards the transition point, with a critical exponent of approximately 0.61. >>

<< These findings align with directional percolation theory, underscoring the robustness of the theoretical framework. >>

Masaya Endo, Rei Kurita. Critical-like behavior in foam dynamics: Transition from slip to scraping. Phys. Rev. Research 7, 023013. Apr 3, 2025.

https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.7.023013

Also: bubble, foam, jamming, transition, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, bubble, bubble rearrangements, foam, jamming, transition, criticality, scraping,  percolation

# gst: friction-induced bubble edge curvature in flowing 2D confined foams

AA << investigate the flow of quasi-2D liquid foams, composed of a single monolayer of bubbles in close contact and confined between two glass plates in a Hele-Shaw cell, with a specific emphasis on understanding how bubble shapes evolve in response to varying flow speeds. Utilizing an experimental setup capable of displacing a substantial number of bubbles in the spanwise direction, while the bubble shapes remain stationary as the bubbles themselves are advected in a plug flow, (They) reveal an average bubble anisotropy characterized by elongated bubbles in the streamwise direction and curved bubble edges in a preferential orientation. >>

<< Notably, these effects intensify with increasing flow speeds. While the bubble anisotropy is created at the entrance of the cell, (AA) study establishes a clear connection between bubble edge curvature and orientation, confinement thickness, frictional forces with the plates, and the inherent anisotropy of the bubbles. >>

Christophe Raufaste, Lauren Rose, et al. Friction-induced bubble edge curvature in flowing two-dimensional confined foams. Phys. Rev. Fluids 10, 023301. Feb 5, 2025. 

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.10.023301 

Also: bubble, foam, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, bubble, foam, friction, surface tension

# gst: porous substrates and foams on the structure of turbulent boundary layers over them.

<< Turbulent flow over and past porous surfaces is encountered in many engineering problems, ranging from flow over forest canopies (..) to flows over and past river beds (..). This makes the understanding or the flow behaviour over porous surfaces crucial. >>

️

<< The present study shows that transition from thick to thin substrate flow behavior depends not only on thickness-to-pore ratio (..) but also on substrate density relative to viscous scales of the flow. >>️

Prateek Jaiswal, Bharathram Ganapathisubramani. Effects of porous substrates on the structure of turbulent boundary layers. arXiv: 2301.04102v1 [physics.flu-dyn]. Jan 10, 2023.

https://arxiv.org/abs/2301.04102

Also

keyword 'turbulence' in FonT

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

keyword 'turbolento' | 'turbolenza' in Notes (quasi-stochastic poetry)

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

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

Keywords: gst, turbulence, turbulent layers, porosity, porous substrates, foam

# gst: apropos of (multitudes) of transitional droplets, when a liquid film collapses in a foam ...

<< Foams have unique properties that distinguish them from ordinary liquids and gases, and are ubiquitously observed in nature, both in biological systems and industrial products. >>

️

<< Once a crack appears near the border and a collapse front is formed, (AA) find that the curvature of the front reverses as it migrates, followed by the emergence and emission of droplets. (they) elucidate the origins of this behavior and discuss the stability of foams, establishing how the characteristic time scales of the process relate to each other. >>️

Naoya Yanagisawa, Marie Tani, Rei Kurita. Dynamics and mechanism of liquid film collapse in a foam. Soft Matter. 17, 1738-1745. Feb 17, 2021.

https://pubs.rsc.org/en/content/articlelanding/2021/SM/D0SM02153A#

Also

keyword 'foam' in FonT

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

keyword 'collapse' in FonT

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

keyword 'schiuma' in Notes

(quasi-stochastic poetry)

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

# gst: the dynamics of a collective bubble (in a foam) that collapse in a droplet

<< Foams have unique properties that distinguish them from ordinary liquids and gases, and are ubiquitously observed in nature, both in biological systems and industrial products. (..) understanding how bubbles in a foam collapse is an important aspect for product longevity and tailoring physical properties. >>

<< Once a crack appears near the border and a collapse front is formed, (AA) find that the curvature of the front reverses as it migrates, followed by the emergence and emission of droplets. >>

<<  It is particularly interesting to note how the shape of the front changes as it migrates. >>

Naoya Yanagisawa, Marie Tani, Rei Kurita. Dynamics and mechanism of liquid film collapse in a foam. Soft Matter 17, 1738-45. doi: 10.1039/ D0SM02153A. Feb 17, 2021.

https://pubs.rsc.org/en/content/articlelanding/2021/SM/D0SM02153A#!divAbstract   

<< An initial crack in a film creates a RVPB (released vertical plateau border). A second crack event in the film causes a "collapse front" to be formed which sweeps up the RVPB before its shape begins to flatten and invert, finally leaving a droplet. >>

When foams collapse (and when they don't). Tokyo Metropolitan University. Mar 01, 2021. 

https://phys.org/news/2021-03-foams-collapse-dont.html   

Also

keyword 'drop' or 'droplet' in FonT

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

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