# 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. >>

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<< 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

# chem: it can stay squishy at the coldest temperatures

<< Normal materials become brittle in deep cryogenic conditions, but a new graphene-based foam (..) stays as flexible as ever. >>

Maria Temming. A new graphene foam stays squishy at the coldest temperatures. Apr 12, 2019.

https://www.sciencenews.org/article/new-graphene-foam-squishy-coldest-temperatures

AA << report wide temperature–invariant large-strain super-elastic behavior in three-dimensionally cross-linked graphene materials that persists even to a liquid helium temperature of 4 K, a property not previously observed for any other material. >>

Kai Zhao, Tengfei Zhang, et al. Super-elasticity of three-dimensionally cross-linked graphene materials all the way to deep cryogenic temperatures. Science Advances  12 Apr 2019: Vol. 5, no. 4, eaav2589. doi: 10.1126/sciadv.aav2589

https://advances.sciencemag.org/content/5/4/eaav2589

# gst: apropos of bubbles, how simple foams collapse

<< When a bubble breaks, (AA) found that a collapse event propagates via impact with the receding film and tiny scattered droplets breaking other bubbles. >>

<< A key finding was that changing the viscosity of the fluid did not lead to a significant change in the number of bubbles broken. Methods to stabilize foams commonly rely on changing the viscosity, yet the team's findings clearly show how both the number of bubbles collapsed and the velocity of the receding film are unaffected. >>

Two distinct physical mechanisms identified for how simple foams collapse. Tokyo Metropolitan University. June 10, 2019.

https://m.phys.org/news/2019-06-distinct-physical-mechanisms-simple-foams.html

Naoya Yanagisawa, Rei Kurita. In-situ observation of collective bubble collapse dynamics in a quasi-two-dimensional foam. Scientific Reports 9, Article number: 5152. March 26, 2019

https://www.nature.com/articles/s41598-019-41486-6

# 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. >>

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<< 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 instability, bubbles may have unexpected chills

<< Bubbles are ubiquitous, existing in everything from the foam on a beer to party toys for children. Despite this pervasiveness, there are open questions on the behavior of bubbles, such as why some bubbles are more resistant to bursting than others. >>️

AA << created a soap bubble from a mixture made of dishwashing liquid, water, and glycerol. They then measured the soap film’s temperature under a variety of environmental conditions. They found that the film could be up to 8 °C colder than the surrounding air. They also found that glycerol content of the soap film impacted this temperature difference, with films containing more glycerol having higher temperatures. Boulogne (Francois Boulogne) says that such a large temperature difference could impact bubble stability.  >>️

Anna Napolitano. Bubbles Have an Unexpected Chill. Physics 15, s173. Dec 19, 2022. 

https://physics.aps.org/articles/v15/s173

Francois Boulogne, Frederic Restagno, Emmanuelle Rio. Measurement of the Temperature Decrease in Evaporating Soap Films. Phys. Rev. Lett. 129, 268001. Dec 19, 2022.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.268001

Also

keyword "bubble" in FonT

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

keyword "bolla" | "bolle" in Notes (quasistochastic-poetry): 

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

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

Keywords: gst, bubble, stability, evaporation, burst