# gst: apropos of 1or2achoos (e.g. from Wuhan), the dynamics of turbulence in a fluid puff

<< Turbulence is everywhere -- in the movement of the wind, the ocean waves and even magnetic fields in space. It can also be seen in more transient phenomena, like smoke billowing from a chimney, or a cough. (..) Understanding this latter type of turbulence -- called puff turbulence -- is important not only for the advancement of fundamental science, but also for practical health and environmental measures, >>️

<< The very nature of turbulence is chaotic, so it's hard to predict, (..) Puff turbulence, which occurs when the ejection of a gas or liquid into the environment is disrupted, rather than continuous, has more complicated characteristics, so it's even more challenging to study. But it's of vital importance -- especially right now for understanding airborne transmission of viruses like SARS-CoV-2. >>️ Marco Edoardo Rosti. 

<< The new model, (..) includes how minute fluctuations within the puff behave, and how both large-scale and small-scale dynamics are impacted by changes in temperature and humidity. (..) at cooler temperatures (15°C or lower), (AA) model deviated from the classical model for turbulence. >>️

<< In the classical model, turbulence reigns supreme -- determining how all the little swirls and eddies within the flow behave. But once temperatures dipped, buoyancy started to have a greater impact. >>

<< The effect of buoyancy was initially very unexpected. It's a completely new addition to the theory of turbulent puffs,>> Marco Edoardo Rosti. ️

Secrets of COVID-19 transmission revealed in turbulent puffs. Okinawa Institute of Science and Technology (OIST). Aug 26, 2021. 

https://www.sciencedaily.com/releases/2021/08/210826111729.htm

Andrea Mazzino, Marco Edoardo Rosti. Unraveling the Secrets of Turbulence in a Fluid Puff. Phys. Rev. Lett. 127, 094501. Aug 25, 2021. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.094501

Also

keyword 'drop' | 'droplet' in FonT:

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

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

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

keyword 'virus' | 'sars-cov-2' | 'sars' in FonT: 

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

https://flashontrack.blogspot.com/search?q=sars-cov-2

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

keyword 'virus' in Notes (quasi-stochastic poetry):

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

# 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

# gst: apropos of 'transitions', slow dynamics of complex connected networks can control the rate of demixing

<< A space- spanning network structure is a basic morphology in phase separation of soft and biomatter, alongside a droplet one. Despite its fundamental and industrial importance, the physical principle underlying such network- forming phase separation remains elusive. >>

AA << find that phase- separation dynamics is controlled by mechanical relaxation of the network- forming dense phase, whose limiting process is permeation flow of the solvent for colloidal suspensions and heat transport for pure fluids. This universal coarsening law would contribute to the fundamental physical understanding of network-forming phase separation. >>

Michio Tateno, Hajime Tanaka. Power-law coarsening in network-forming phase separation governed by mechanical relaxation. Nat Commun 12, 912. doi: 10.1038/  s41467-020-20734-8. Feb 10,  2021.

https://www.nature.com/articles/s41467-020-20734-8

️

Discovery of a new law of phase separation. University of Tokyo. Feb 10, 2021. 

https://phys.org/news/2021-02-discovery-law-phase.html

Also

keyword 'transition' in FonT

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

keyword 'transition' | 'transizion*' in Notes (quasi-stochastic poetry)

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

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

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

# gst: observing the crystallization process in a droplet

<< Crystallization is the assembly of atoms or molecules into highly ordered solid crystals, which occurs in natural, biological, and artificial systems. However, crystallization in confined spaces, such as the formation of the protein shell of a virus, is poorly understood. Researchers are trying to control the structure of the final crystal formed in a confined space to obtain crystals with desired properties, which requires thorough knowledge of the crystallization process. >>

AA << used a droplet of a colloid—a dispersion of liquid particles in another liquid, like milk—as a model for single atoms or molecules in a sphere. Unlike single atoms or molecules, which are too small to easily observe, the colloid particles were large enough to visualize using a microscope. This allowed the researchers to track the ordering of single particles in real time during crystallization. >>

<< We visualized the organization process of colloid particles in numerous droplets under different conditions to provide a picture of the crystallization process in a sphere, >> Peng Tan

<< Based on their observations, the team proposed that the crystallization process involved three stages: initial ordering on the surface "skin" of the droplet, nucleation and growth in the core of the droplet, and then slow ripening of the whole structure. First, a skin consisting of a single layer of ordered colloid particles rapidly formed on the droplet surface. Next, crystallization occurred in the core of the droplet, far from the crystallized skin. The competition between crystallization in these two regions controlled the structure of the final crystal. The researchers found that the "soft" (long-range) interactions between the negatively charged colloid particles affected their organization and the resulting crystal structure. These soft interactions are dominated by kinetics, that is, the interactions that form the fastest, rather than those that use the least energy to give the thermodynamically stable structure, illustrating that kinetics plays an important role in crystallization in a confined space. It was already known that thermodynamics contributes strongly to the final structure of crystals. >>

Having a ball: Crystallization in a sphere. University of Tokyo. Sep 21, 2020.

https://phys.org/news/2020-09-ball-crystallization-sphere.html

Chen Y., Yao Z., et al. Morphology selection kinetics of crystallization in a sphere. Nat. Phys. doi: 10.1038/ s41567-020-0991-9. Sep 21, 2020.

https://www.nature.com/articles/s41567-020-0991-9

Also

Control of material crystallization by agitation. Osaka University. Jun 08, 2017.

https://phys.org/news/2017-06-material-crystallization-agitation.html

keyword 'drop' or 'droplet' in FonT

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

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

# gst: apropos of the variety in the ways liquid jets break up

<< When a liquid exits a nozzle and encounters something it cannot immediately mix into—a gas, for example—it forms a cylinder. Quickly, small surface perturbations and various forces cause the liquid tube to break apart into droplets. The entire cylinder either pinches off into droplets one at a time at the tip, takes on a wavy or corkscrew-like structure, or atomizes into a fine spray. >> 

<< Our results show that the gas and liquid flows are equally important in the interface region, an idea neglected by most other studies, (Nathan Speirs).  The irregular shapes of the droplets formed are quite interesting as well, (Kenneth Langley) >> 

<< There's so much variety in the ways liquid jets break up. (Nathan Speirs) >>  

King Abdullah. Slippery superfluids push jets to breaking point. University of Science and Technology. Aug 31, 2020. 

https://phys.org/news/2020-08-slippery-superfluids-jets.html 

<< Past studies have shown that liquid jet breakup behavior can be classified into five regimes: Rayleigh, first wind, sinuous, second wind, and atomization. By experimentally examining the breakup of superfluid and normal liquid 4^He in an atmosphere of its own vapor, (AA) investigate the evolution of the jet behavior >>

N. B. Speirs, K. R. Langley, et al. Jet breakup in superfluid and normal liquid  4^He. Phys. Rev. Fluids 5, 044001. Apr 2, 2020.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.5.044001    

# gst: interface mobility enhances the bounce effect of bubbles

<< Theoretically, when a bubble reaches the surface of a pure liquid, the thin film of liquid between the bubble and the air above should quickly drain away, allowing the bubble to coalesce with the air. The same would be expected when two bubbles meet within the liquid or when two droplets of oil come together in water.  >>

<< Counterintuitively, bubbles or droplets reaching the highly mobile fluorocarbon liquid-air interface bounced off of the interface much more strongly than from the immobilized interface. The reason is that there is less friction on the mobile interface and thus less energy is lost during the bounce. "To our knowledge, our studies and simulations are the first to demonstrate an enhanced bounce effect due to interface mobility," >> Ivan U. Vakarelski.

When bubbles bounce back.  King Abdullah University of Science and Technology. Nov 13, 2019.

https://m.phys.org/news/2019-11-when-bubbles-bounce-back.html

Ivan U. Vakarelski, Fan Yang, et al. 

Mobile-surface bubbles and droplets coalesce faster but bounce stronger. Science Advances  25 Oct 2019:

Vol. 5, no. 10, eaaw4292 DOI: 10.1126/sciadv.aaw4292 

https://advances.sciencemag.org/content/5/10/eaaw4292

# gst: spontaneous spin-sliding of volatile drops

<< When a volatile solvent droplet is deposited on a freely floating swellable sheet, it can spontaneously become lobed, asymmetric, and either spin, slide or move via a combination of the two.  This process of symmetry-breaking is a consequence of the solvent droplet swelling the membrane and its inhomogeneous evaporation from the membrane, coupled with the hydrodynamics within the droplet. By tuning the membrane thickness and the droplet size, (AA) find a critical threshold that determines the transition from a quiescent spherical cap state to a self-piloted motile state.>>

Aditi Chakrabarti, Gary P. T. Choi, L. Mahadevan. Spontaneous spin-sliding of volatile drops on swelling sheets. arXiv:1910.07064v1 [cond-mat.soft]  Oct 15, 2019. 

https://arxiv.org/abs/1910.07064