# gst: apropos of transitions, droplet trajectories during single and collective bursting bubbles

<< Mechanisms of droplet production from bursting bubbles have been extensively studied for single bubbles, but remain sparsely investigated in more complex collective settings. >>️

<< In the collective bubbling experiment, subsurface quasimonodisperse bubbles are rising up to the surface where, depending on the surfactant concentration, they can either merge or assemble in rafts of monodisperse bubbles. Drop trajectories are recorded, analyzed, and shown to exhibit uniquely distinctive features for the different production mechanisms: centrifuge film drops are ejected sideways, and jet drops are ejected vertically. Different single-burst scalings are finally compared to the experimental size-velocity relationships, and reveal that drops coming from collective bubble bursting appear slower and more scattered than when coming from single bursting bubbles. >>️

B. Neel and L. Deike. Velocity and size quantification of drops in single and collective bursting bubbles experiments. Phys. Rev. Fluids 7, 103603. Oct 5, 2022. 

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.7.103603

Also: 'when a superbubble can generate trains of shock waves'. Mar 6, 2019.

https://flashontrack.blogspot.com/2019/03/gst-astro-when-superbubble-can-generate.html

Also: 'transition', 'droplet', 'droploid', 'bubble', in: https://www.inkgmr.net/kwrds.html

Keywords: gst, transition, drop, droplet, droploid, bubble, collective dynamics,  fluid dynamics

PS: << they can either merge or assemble in rafts of monodisperse bubbles >> ; this is poetry, without unnecessary adjectives, anzicheforse ... FonT. Wed June 14, 2023 16:58 (cest)

# gst: the physiological emergence and evolution of cell-spanning vortices (inside Drosophila oocytes).

<< Life in complex systems, such as cities and organisms, comes to a standstill when global coordination of mass, energy, and information flows is disrupted. Global coordination is no less important in single cells, especially in large oocytes and newly formed embryos, which commonly use fast fluid flows for dynamic reorganization of their cytoplasm. Here, (AA) combine theory, computing, and imaging to investigate such flows in the Drosophila oocyte, where streaming has been proposed to spontaneously arise from hydrodynamic interactions among cortically anchored microtubules loaded with cargo-carrying molecular motors. >>️

Sayantan Dutta, Reza Farhadifar, et al. Self-organized intracellular twisters. arXiv: 2304.02112v2 [physics.bio-ph].  Apr 6, 2023. 

https://arxiv.org/abs/2304.02112

Also

keyword 'vortex' in FonT

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

keyword 'vortice' in Notes

(quasi-stochastic poetry)

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

Keywords: gst, fluid dynamics, vortex, vortices, vortexes, vorticity,

# gst: even a single bubble can produce creative musical outcomes

<< Producing original and arranging existing musical outcomes is an art that takes years of learning and practice to master. Yet, despite the constant advances in the field of AI-powered musical creativity, production of quality musical outcomes remains a prerogative of the humans. Here we demonstrate that a single bubble in water can be used to produce creative musical outcomes, when it nonlinearly oscillates under an acoustic pressure signal that encodes a piece of classical music. >>️

Ivan S. Maksymov. Musical creativity enabled by nonlinear oscillations of a bubble in water. arXiv:2304.00822v1 [cs.SD]. Apr 3, 2023. 

https://arxiv.org/abs/2304.00822

keyword "bubble" in FonT

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

Keywords: gst, ai, fluid dynamics, bubble, sound, music, audio processing

# gst: behavior of microswimmers in a vortex with translational and rotational noise

AA << propose a theoretical model to investigate the dynamics of elongated microswimmers in elementary vortices, namely active particles in two- and three-dimensional rotlets. A deterministic model first reveals the existence of bounded orbits near the centre of the vortex and unbounded orbits elsewhere. (AA) further discover a conserved quantity of motion that allows (..) to map the phase space according to the type of the orbit (bounded vs unbounded). (They) next introduce translational and rotational noise into the system. Using a Fokker--Planck formalism, (AA) quantify the quality of trapping near the centre of the vortex by examining the probability of escape and the mean time of escape from the region of deterministically bounded orbits. (AA) finally show how to use these findings to formulate a prediction for the radius of the depletion zone, which compares favourably with the experiments of Sokolov and Aranson (2016). >>

Ivan Tanasijevic, Eric Lauga. Microswimmers in vortices: Dynamics and trapping. arXiv: 2211.05866v1 [physics.bio-ph].  Nov 10, 2022. 

https://arxiv.org/abs/2211.05866

Also

'microswimmers' in FonT 

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

Keywords: gst, behav, translation,  rotation, trapping, noise, swimmer, swimming,  microswimmers, fluid dynamics, vortex, vortices, vortexes, vorticity

# gst: the effect of noise on the dynamics of microswimmers in externally-driven fluid flows.

AA << have quantified the effect of noise on swimmer dynamics in a steady, two-dimensional hyperbolic fluid flow. In such a flow, swimmers are ultimately forced to escape to the left or the right, with their transient dynamics near the passive unstable fixed point determining which way they go. >>

<< Without noise, a swimmer’s fate is sealed based on its position relative to the SwIM (swimming invariant manifolds) in the xθ phase space. With noise, the swimmer’s motion is a stochastic process. >>

AA << calculated the steady-state orientation distributions of diffusive, run-and-tumble, or mixed swimmers in the hyperbolic flow. The fluctuations give some swimmers greater opportunity to cross the SwIM and exit on the opposite side than they would have without noise. There is however a maximal distance that swimmers can get on either side of the passive fixed point and still be able to swim back to the other side—this is where the stable BIMs (burning invariant manifolds) block inward swimming particles. >>

<< Fluctuations make it increasingly likely that a swimmer close to one of these BIMs does indeed end up crossing it, causing irreversible changes to the fluctuating swimmers’ trajectories (assuming negligible translational diffusion).  >>️

Simon A. Berman, Kevin A. Mitchell. Swimmer dynamics in externally-driven fluid flows: The role of noise. arXiv: 2108.10488v1 [physics.flu-dyn]. Aug 24, 2021.

https://arxiv.org/abs/2108.10488

keywords: gst, swimmer, swimming particle, fluid dynamics, chaotic dynamics, rotational diffusion, random fluctuation, tumbling, noise

# gst: streak-vortex instabilities in heterogeneous turbulent boundary layers

AA << re-examine the turbulent boundary layers developing over surfaces with spanwise heterogeneous roughness of various roughness wavelengths 0.32≤S/δ¯¯≤3.63, where S is the width of the roughness strips and δ¯¯ is the spanwise-averaged boundary-layer thickness. >>

<< The heterogeneous cases induce counter-rotating secondary flows, and these are compared to the large-scale turbulent structures that occur naturally over the smooth wall. Both appear as meandering elongated high- and low-momentum streaks in the instantaneous flow field. >>

<< Results suggest that the secondary flows might be spanwise-locked turbulent structures, with S/δ¯¯ governing the strength of the turbulent structures and possibly the efficacy of the surface in locking the structures in place (most effective when S/δ¯¯≈1). >>

<< Conditional averages of the fluctuating velocity fields of both spanwise heterogeneous and smooth wall cases result in structures that are strongly reminiscent of the streak-vortex instability model. (proposed in Jeong et al.,1997) >>

<< One outstanding question that remains unanswered in the present study is the cause of the prominent meandering of the turbulent structures, which is only observed when S/δ¯¯≈1 >>️️

️

Dea Daniella Wangsawijaya, Nicholas Hutchins. Investigation of unsteady secondary flows and large-scale turbulence in heterogeneous turbulent boundary layers. arXiv: 2110.02268v1 [physics.flu-dyn]. Oct 5, 2021.

https://arxiv.org/abs/2110.02268

keywords: gst, fluid dynamics, vortices, vortex instability, streak-vortex instability,  roughness, heterogeneous roughness, turbulence, turbulent boundary layers.

# gst: the sounds that occur when a soap bubble pops.

<< The popping sound of a bursting soap bubble is acquired using microphone arrays and analyzed using spherical harmonics decomposition. >>

the << acoustic emission originates mainly from the capillary stresses exerted by the liquid soap film on the air and that it quantitatively reflects the out-of-equilibrium evolution of the flowing liquid film. (..) the acoustic signature of violent events of physical or biological origin could be used to measure the forces at play during these events. >>

Adrien Bussonniere, Arnaud Antkowiak, et al. Acoustic Sensing of Forces Driving Fast Capillary Flows. Phys. Rev. Lett. 124, 084502 Feb 27, 2020.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.084502

Bob Yirka. Measuring the sound of a soap bubble popping. Phys.org. Mar 2, 2020.

https://m.phys.org/news/2020-03-soap.html

# gst: apropos of turbulences close to a wall, the repetitive structure of a vortex

<< At the boundary where a fluid flows over a fixed structure, a turbulent boundary layer is created where the fluid interacts with the wall, creating eddies in the current. These eddies may seem to be random on first glance, but they actually create distinct patterns, with countless tiny eddies close to the wall; fewer but larger eddies located a little farther out; and even fewer, but still larger, eddies beyond those. >>

<< "We knew that, underlying these very complicated structures, there had to be a very simple pattern. We just didn't know what that pattern was until now," says McKeon, who next plans to dig deeper into the model to quantify just how many eddies should be included to create an accurate representation of the whole. >>

Engineers exploit the repeating structure of turbulence to create a more complete model of the phenomenon. California Institute of Technology. Nov 6, 2019.

https://m.phys.org/news/2019-11-exploit-turbulence-phenomenon.html

Beverley J. McKeon. Self-similar hierarchies and attached eddies. Phys. Rev. Fluids 4, 082601(R). Aug 26, 2019.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.4.082601

# gst: exploring the lifespan of a liquid droplet

<< Current theories state that the droplet's diameter-squared decreases in proportion to time (classical law); however, this period only accounts for a small portion of the drop's evolution. As the diameter approaches the unobservable micro- and nano-scale, molecular dynamics have to be used as virtual experiments and these show a crossover to a new behaviour, with the diameter now reducing in proportion to time (nano-scale law). >>

<< It is fascinating that intuition based on everyday observations are a hindrance when attempting to understand nanoscale flows, so that, as in this research, one has to lean on theory to enlighten us. >>  James Sprittles.

The lifespan of an evaporating liquid drop. University of Warwick. Oct 10, 2019.     https://m.phys.org/news/2019-10-lifespan-evaporating-liquid.html

Rana A.S., Lockerby D.A., Sprittles J.E.  Lifetime of a Nanodroplet: Kinetic Effects and Regime Transitions. Phys. Rev. Lett. 123, 154501 Oct 9, 2019.     https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.154501   

# gst: the creation of giant bubbles is underappreciated in sci res

<< In the pantheon of scientific achievement, the creation of giant soap bubbles is sadly underappreciated. >>

<< "How are such large films created, and how do they remain stable?" ask Frazier (Stephen Frazier) and co. >>

The chemistry behind how you make a record-breaking giant soap bubble.
The art of creating giant bubbles is more mysterious than it seems, but researchers are at last teasing apart the chemistry of thin soapy films. Emerging Technology from the arXiv.  Aug 24, 2019.  
https://www.technologyreview.com/s/614181/the-chemistry-behind-how-you-make-a-record-breaking-giant-soap-bubble/      

https://twitter.com/techreview/status/1166167505246871552

Stephen Frazier, Xinyi Jiang, Justin C. Burton. How to make a giant bubble.
arXiv:1908.00537v1 [physics.flu-dyn] Aug 1, 2019. 

https://arxiv.org/abs/1908.00537

FonT

a proposito di generica "creation of giant bubbles", una entita' AI, anche di "media forza", opportunamente orientata per le pulsioni sperimentali, ci giochera' alla grande, io penso ...

Anomalous formation of molecules after vapor deposition. FonT. Dec 31, 2015.   

https://flashontrack.blogspot.com/2015/12/rmx-s-gst-anomalous-formation-of.html