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Visualizzazione dei post in ordine di data per la query turbulence. Ordina per pertinenza Mostra tutti i post
Visualizzazione dei post in ordine di data per la query turbulence. Ordina per pertinenza Mostra tutti i post

lunedì 6 maggio 2024

# gst: random walk model for dual cascades in wave turbulence.

<< Dual cascades in turbulent systems with two conserved quadratic quantities famously arise in both two-dimensional hydrodynamic turbulence and also in wave turbulence based on four-wave interactions. >>

<< in wave turbulence the systematic spectral fluxes observed in a dual cascade do not require an irreversible dynamical mechanism, rather, they arise as the inevitable outcome of blind chance. >>️️

Oliver Bühler. Random walk model for dual cascades in wave turbulence. Phys. Rev. E 109, 055102. May 1, 2024. 

Also: waves, turbulence, random, weak, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, waves, turbulence, weak turbulence, random, random walks


giovedì 14 dicembre 2023

# gst: pulsating active matter.

<< the mechanical pulsation of locally synchronized particles is a generic route to propagate deformation waves. >>
AA << consider a model of dense repulsive particles whose activity drives periodic change in size of each individual. >>️

They << show that the competition between repulsion and synchronization triggers an instability which promotes a wealth of dynamical patterns, ranging from spiral waves to defect turbulence. >>️

Yiwei Zhang, Etienne Fodor. Pulsating Active Matter. Phys. Rev. Lett. 131, 238302. Dec 8, 2023. 

Also: waves, particle, transition, instability, turbulence, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, waves, particle, transition, instability, turbulence


lunedì 27 novembre 2023

# gst: when a turbulence can be confined

<< Turbulence is hard to control. Its ephemeral nature prevents us from treating it as an ordinary state of matter. Here (AA) create a stationary and isolated blob of turbulence using only elemental building blocks: vortex rings.  The turbulence is confined in a spherical region, surrounded by a quiescent environment, initiated and sustained by vortex rings. Crucially, vortex rings can be endowed with conserved quantities such as energy and helicity, which can be transferred to the turbulent state. Using 2D particle image velocimetry and 3D particle tracking velocimetry, (AA) demonstrate how confinement of turbulence occurs when vortex rings repeatedly collide, in contrast to coherent vortex reconnections. The pathlines depict the difference between these states of flow. >>️

Takumi Matsuzawa, Noah P. Mitchell, Stéphane Perrard, William T. M. Irvine. Turbulence through sustained vortex ring collisions. Phys. Rev. Fluids 8, 110507. Nov 16, 2023.

75TH ANNUAL MEETING OF THE APS DIVISION OF FLUID DYNAMICS (NOVEMBER 20, 2022 — NOV 22, 2022). V0008: Turbulence through sustained vortex ring collisions. 

Also: turbulence, vortex, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, turbulence, vortex, vortex ring collisions



martedì 26 settembre 2023

# gst: apropos of transitions, three distinct new families of long-wave instabilities and potential new pathways to turbulence.


AA << reveal three previously unknown instabilities, distinct from the well-known Kelvin-Helmholtz Instability (KHI) and Holmboe Wave Instability (HWI), in that they have longer wavelengths (..) and often slower growth rates. >>

<< The circumstances under which turbulence can persist in strongly stratified flows remains a fascinating debate within the community. [AA] demonstrated that weakly unstable (very) long waves may trigger turbulence and mixing after long periods of time, even under initially very strongly stratified conditions. >>

Lu Zhu, Amir Atoufi, Adrien Lefauve, Rich R. Kerswell, P. F. Linden. Long-wave instabilities of sloping stratified exchange flows. arXiv:2309.10056v1 [physics.flu-dyn]. Sep 18, 2023.

Also: waves, instability, transition, turbulence, chaos, in https://www.inkgmr.net/kwrds.html

Keywords: gst, waves, instability, long-wave instability, transition, turbulence, chaos





mercoledì 20 settembre 2023

# gst: apropos of collisions of a vortex dipoles, vortex unbinding, vortex pinning to the edge, and emission of rarefaction pulses.

<< Vortices and dark solitons are fundamental defects that appear in nonlinear physics at all scales, from nonlinear optics to cosmic fluids. In two or three dimensions, dark solitons are fundamentally connected to highly ordered vortex states through an intrinsic modulation instability in the surrounding matter. >>️

<< Here, [AA] report an experimental realization of ring dark soliton (RDS)  generation in a two-dimensional atomic superfluid trapped in a circular box. By quenching the confining box potential, [they] observe an RDS emitted from the edge and its peculiar signature in the radial motion. As an RDS evolves, [they] observe transverse modulations at discrete azimuthal angles, which clearly result in a patterned formation of a circular vortex dipole array. Through collisions of the vortex dipoles with the box trap, [they] observe vortex unbinding, vortex pinning to the edge, and emission of rarefaction pulses. >>

Hikaru Tamura, Cheng-An Chen, Chen-Lung Hung. Observation of Self-Patterned Defect Formation in Atomic Superfluids–from Ring Dark Solitons to Vortex Dipole Necklaces. Phys. Rev. X 13, 031029. Sep 14, 2023. 

Also: soliton, vortex, turbulence, waves, in: https://www.inkgmr.net/kwrds.html  

Keywords: gst, soliton, dark soliton, vortex, turbulence, waves. 


giovedì 13 luglio 2023

# gst: complex flows by hairpin vortices behind hills with different scales


 << In the flow around protuberance, separation bubbles occur ahead and behind the protuberance, and a coherent vortex structure exists in the wake. In such a flow field, heat, substance, and momentum are actively transported by the vortex. (..) When multiple protuberances are set in the flow, the wakes of the protuberances interfere with each other, resulting in complicated flows. >> 

 << This study performed a numerical analysis of the hairpin vortex and heat transport generated by the interference of the wakes behind two hills in a laminar boundary layer. In the case of hills with the same scale, the interference between hairpin vortices in the wake is more intensive than in the different-scale hills. When the hills with different scales are installed, hairpin vortices with different scales are periodically shed. >> 
 
  << Regardless of the scale ratio of the hills, when the hill spacing in the spanwise direction is narrowed, the asymmetry of the hairpin vortex in the wake increases due to the interference between the wakes. At this time, the turbulence caused by the leg and the horn-shaped secondary vortex on the spanwise center side in the hairpin vortex increases, and heat transport around the hairpin vortex becomes active. >> 
 
Hideki Yanaoka, Tatsuya Hamada. Hairpin vortices and heat transfer in the wakes behind two hills with different scales. arXiv: 2306.17365v1 [physics.flu-dyn]. Jun 30, 2023. 

Also: vortex, turbulence in https://www.inkgmr.net/kwrds.html

Keywords: gst, vortex, hairpin vortex, turbulence


martedì 11 luglio 2023

# life: declining towards turbulence, thus ecstatic (detotuthec)


(1/3) for our birthdays on July 11th (*1th) and July 25th (*9th) ... forever Nomads (*), curious, young.  
@flashontrack  11:36 11lug21

(2/3) (*) e.g. exotic, maverick, agnostic,  track seeker, meta-mechanic pulsating manipulator, ockhamistic, erratic, chaotic, #detotuthec (declining towards turbulence, thus ecstatic), ab-normal ...
@flashontrack 11:37 11lug21

(3/3) with mindfulness, compassion and tenacity, where also vengeance consists in (try) saving others (whatever 'others' means).
@flashontrack 11:38 11lug21

Keywords: detotutech, detect thou

martedì 27 giugno 2023

# gst: laminar and turbulent flows detected in music, a fluid framework approach

<< The relationship between musical material and physical phenomena has become a topic in the musicological literature over the last several decades, particularly concerning elements of the musical system itself, and constructions found in the work of contemporary classical composers such as Gyorgy Ligeti and Iannis Xenakis. Most scholars, who adopt this approach, explore the physical phenomena of fractals in the analysis of musical works, but fluid mechanical frameworks, such as laminar and turbulent flows, offer a new avenue to be explored. In this paper (AA) will propose a novel method of musical analysis for examining musical structures in terms of fluid-like behaviour such that Ligeti etude no. 9 serves as a model, whereby the metaphors of laminar and turbulent flows take precedence. >>

Noah Chuipka. Musico-acoustic Depictions of Laminar and Turbulent Flows in Ligeti Piano Etude No. 9 and a Novel Method of Analysis. arXiv: 2306.10093v1 [cs.SD]. Jun 17, 2023. 

Also: music, jazz, turbulence, in https://www.inkgmr.net/kwrds.html

Keywords: gst, music, jazz, turbulence


giovedì 22 giugno 2023

# gst: the effects of order- disorder on a system of swarmalators that move on a one-dimensional ring.


<< Swarmalators are phase oscillators that cluster in space, like fireflies flashing on a swarm to attract mates. >>

<< In this work, (AA) explore the effects of disorder induced by phase frustration on a system of Swarmalators that move on a one-dimensional ring. >>

They find << numerically and analytically, the ordered and disordered states that emerge in the system. The active states, not present in the model without disorder, resemble states found previously in numerical studies for the 2D Swarmalators system. One of these states, in particular, shows similarities to turbulence generated in a flattened media. (AA) show that all ordered states can be generated for any values of the coupling constants by tuning the phase frustration parameters only. Moreover, many of these combinations display multi-stability. >>️

Joao U.F. Lizarraga, Marcus A.M. de Aguiar. Sakaguchi Swarmalators. arXiv: 2305.08615v1 [nlin.PS]. May 15, 2023. 

Also:  'swarm', 'turbulence', 'noise', 'particle' in: https://www.inkgmr.net/kwrds.html

Keywords: gst, swarm, turbulence, noise, particle




domenica 14 maggio 2023

# jazz: when turbulence underneath it and on top of it.


<< The album title comes from poet and scholar Fred Moten, who described Gamedze's drumming in the internet forum Poesis as an "amazing interplay between turbulence and pulse. Pulse is supposed to regulate and also be regular, but the turbulence underneath it and on top of it, it's just extraordinary." >>️

Thom Jurek. Turbulence and Pulse. allmusic.com. May 5, 2023. 

Also: jazz, turbulence, in  https://www.inkgmr.net/kwrds.html

Keywords: jazz, turbulence



sabato 6 maggio 2023

# gst: nematic order condensation and topological defects in inertial active nematics


<< Living materials at different length scales manifest active nematic features such as orientational order, nematic topological defects, and active nematic turbulence. Using numerical simulations (AA) investigate the impact of fluid inertia on the collective pattern formation in active nematics. >>️

<< an incremental increase in inertial effects due to reduced viscosity results in gradual melting of nematic order with an increase in topological defect density before a discontinuous transition to a vortex-condensate state. The emergent vortex-condensate state at low enough viscosities coincides with nematic order condensation within the giant vortices and the drop in the density of topological defects. (AA) further show flow field around topological defects is substantially affected by inertial effects. (..) no evidence of universal scaling at higher viscosities. >>
Roozbeh Saghatchi, Mehmet Yildiz, Amin Doostmohammadi. Nematic order condensation and topological defects in inertial active nematics. Phys. Rev. E 106, 014705. July 25, 2022.

Also: 'turbulence', 'vortex', 'defect', 'drop' in https://www.inkgmr.net/kwrds.html

Keywords: gst, behavior, collective behavior, patterns, turbulence, nematic turbulence, viscosity, vortex, defect, drop


sabato 29 aprile 2023

# gst: pattern generation through turbulent cascades


<< Fully developed turbulence is a universal and scale-invariant chaotic state characterized by an energy cascade from large to small scales where the cascade is eventually arrested by dissipation. In this Letter, (AA) show how to harness these seemingly structureless turbulent cascades to generate patterns. Conceptually, pattern or structure formation entails a process of wavelength selection: patterns typically arise from the linear instability of a homogeneous state. By contrast, the mechanism (they) propose here is fully non-linear and triggered by a non-dissipative arrest of turbulent cascades. Instead of being dissipated, energy piles up at intermediate scales. Using a combination of theory and large-scale simulations, (AA) show that the tunable wavelength of these cascade-induced patterns is set by a non-dissipative transport coefficient called odd or gyro viscosity. This non-dissipative viscosity is ubiquitous in chiral systems (..). Beyond chiral fluids, cascade-induced pattern formation could occur in natural systems (..) as well as in industrial processes (..). >>

Xander M. de Wit, Michel Fruchart, et al. Pattern formation by non-dissipative arrest of turbulent cascades. arXiv: 2304.10444v1 [cond-mat.soft]. Apr 20, 2023.

Also: 'turbulence', 'vortex', 'game', 'evolution', 'ai' in https://www.inkgmr.net/kwrds.html

Keywords: gst, vortex, vorticity,  turbulence, turbulent cascade, pattern formation, game, evolution, ai (artificial intelligence)




martedì 14 marzo 2023

# 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.

Also

keyword 'turbulence' in FonT

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


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


martedì 21 febbraio 2023

# gst: towards (insights into) intermittency and inhomogeneity of turbulent mixing

<< Fluid elements deform in turbulence by stretching and folding. In this work, by projecting the material deformation tensor onto the largest stretching direction, the dynamics of folding is depicted through the evolution of the material curvature. Results from direct numerical simulation (DNS) show that the curvature growth exhibits two regimes, first a linear stage dominated by folding fluid elements through a persistent velocity Hessian which then transitions to an exponential growth driven by the stretching of already strongly bent fluid elements. This transition leads to strong curvature intermittency at later stages, which can be explained by a proposed curvature-evolution model. The link between velocity Hessian to folding provides a new way to understand the crucial steps in energy cascade and mixing in turbulence beyond the classical linear description. >>

Yinghe Qi, Charles Meneveau, Greg Voth, Rui Ni. Folding dynamics and its intermittency in turbulence. arXiv: 2301.10341v1 [physics.flu-dyn]. Jan 24, 2023. 

Also

keyword 'intermittency' in FonT

keyword 'turbulence' in FonT

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


keyword 'transition' | 'transitional' in FonT


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



Keywords: gst, intermittency, turbulence, transition


lunedì 30 gennaio 2023

# gst: towards the characterization of lines, links, writhes and twists in a vortex.


<< Vorticity in turbulent flows is often organized into complex geometries that influence the dynamics. (AA) use a relatively novel approach to describe these geometries: that of obtaining segments of vortex lines embedded in the flow. This enables to quantify the geometric features of these objects. >>

<< Vortex lines differ widely in their behaviour but (AA) find some unifying features. The decay from high levels of vorticity is shown to happen over a short fraction of the vortex length. The local curvature is inversely related with the vorticity magnitude. Strong parts of vortex lines bundle together. >>

Saumav Kapoor, Rama Govindarajan, Siddhartha Mukherjee. Geometric characterization of vortex lines in turbulence. arXiv: 2301.06808v1 [physics.flu-dyn]. Jan 17, 2023.

Also

keyword 'vortex' in FonT


keyword 'vortice' in Notes
 (quasi-stochastic poetry)


Keywords: gst, vortex, vortices, vortexes, vorticity



mercoledì 6 luglio 2022

# gst: when turbulence is driven by a strongly compressive guide

<< it is not fully understood how shocks drive turbulence, in particular whether shock driving is a more solenoidal (rotational, divergence-free) or a more compressive (potential, curl-free) mode of driving turbulence. >>️

<< Here, (AA) use hydrodynamical simulations of a shock inducing turbulent motions in a structured, multi-phase medium. >>️

<< Using simulations in which a shock is driven into a multi-phase medium with structures of different sizes and Γ<1, (AA) find b∼1 for all cases, showing that shock-driven turbulence is consistent with strongly compressive driving. >>️

Saee Dhawalikar, Christoph Federrath,  et al. The driving mode of shock-driven turbulence. arXiv:2205.14417v1 [astro-ph.GA]. May 28, 2022. 


Also

keywords 'turbulence' in FonT


keywords 'turbolento' in Notes 
(quasi-stochastic poetry)


keyword 'waves' in FonT


keyword 'onda' in Notes 
(quasi-stochastic poetry)


keyword 'instability' | 'instabilities' in FonT



keyword 'instabile' in Notes 
(quasi-stochastic poetry)


Keywords: gst, turbulence, instability, waves, shock waves








sabato 21 maggio 2022

# gst: apropos of transitions, two aspects of intermittency


<< intermittency produces significant probability of rare events that may locally accelerate the collision rates by a large factor in comparison with estimates using typical events. >>

<< Increasing intermittency of turbulence destroys the theory not via stronger bursts, but rather via increase of characteristic sizes of regions of calm and quiescent flow. ([AA️] remind that these two aspects of intermittency go together: increase of regions of calm flow and at the same time increased probability of strong bursts ([8] U. Frisch, Turbulence: The Legacy of A. N. Kolmogorov, (Cambridge University Press, New York, 1995).). >>

Itzhak Fouxon, Seulgi Lee, Changhoon Lee. Intermittency and collisions of fast sedimenting droplets in turbulence.  arXiv:2205.06972v1 [physics.flu-dyn]. May 14, 2022. 


Also

keyword 'intermittency' in FonT


keyword 'intermittenza|e' | 'intermittente|i' in Notes (quasi-stochastic poetry)





Keywords: gst, intermittency, collision, drop, droplet, turbulence


martedì 15 febbraio 2022

# gst: transitional dynamics among gyrotactic (prolate spheroid) swimmers in turbulence


<< In this study, (AA) consider small, elongated, gyrotactic, swimming particles in homogenous isotropic turbulence (..). Many motile phytoplankton species are gyrotactic, i.e., their swimming direction results from the competition between shear-induced viscous torque and the stabilizing torque due to bottom-heaviness. (..)  Moreover, both single phytoplankton cells and multicellular phytoplankton chains can have elongated shapes, which makes the study of gyrotactic active particles with prolate shapes necessary. >>

AA addressed the following problems:
<< (i) How the clustering is affected by the swimming number Φ and the stability number Ψ? In particular, how to characterize the extent of clustering based on the three-dimensional Voronoi analysis?
(ii) How the clustering is related to the flow structures? This question has two perspectives.  From the space perspective, what are the regions that particles accumulate in? From the time perspective, how long do particles exist in an aggregated state? >>

Zehua Liu, Linfeng Jiang, Chao Sun. Accumulation and alignment of elongated gyrotactic swimmers in turbulence. arXiv:2202.04351v1 [physics.flu-dyn]. Feb 9, 2022.


Also

The effect of noise on the dynamics of microswimmers in externally-driven fluid flows.  


keywords 'turbulence' in FonT   


keywords 'turbolento' in Notes (quasi-stochastic poetry)


keywords: transition, swimmers,  gyrotactic swimmers, spheroids,  prolate spheroids, stability, turbulence


mercoledì 1 dicembre 2021

# gst: small-scale random perturbations, Arnold's cat spontaneously stochastic

<< Multi-scale systems (..) may possess a fascinating property of spontaneous stochasticity: a small-scale initial uncertainty develops into a randomly chosen largescale state in a finite time, and this behavior is not sensitive to the nature and magnitude of uncertainty (..). >>

A << intriguing form is the Eulerian spontaneous stochasticity (ESS) of the velocity field itself: an infinitesimal small-scale noise triggers stochastic evolution of velocity field at finite scales and times. >>

AA << prove that a formally deterministic system with scaling symmetry yields a stochastic process with Markovian properties if it is regularized with a vanishing small-scale random perturbation. Besides its significance for understanding turbulence, (their) model extends the phenomenon of ESS beyond the scope of fluid dynamics: (AA) discuss a prototype of a feasible experiment for observing ESS in optics or electronics, as well as potential applications in other physical systems.>>

Alexei A. Mailybaev, Artem Raibekas. Spontaneously stochastic Arnold's cat. arXiv:2111.03666v1 [nlin.CD]. Nov 5,  2021.


keywords: gst, Arnold's cat, randomness, stochasticity, spontaneous stochasticity, small-scale random perturbations, noise, turbulence, chaos 


sabato 30 ottobre 2021

# gst: apropos of transitions, perspectives on viscoelastic flow instabilities; the 'porous individualism'

<< given the observation that disorder can suppress the transition to elastic turbulence in 2D porous media (..), it has been unclear whether and how this transition manifests in disordered 3D media — though elastic turbulence has been speculated to underlie the long-standing observation that the macroscopic flow resistance of an injected polymer solution can abruptly increase above a threshold flow rate in a porous medium, but not in bulk solution >>️

AA << found that the transition to unstable flow in each pore is continuous, arising due to the increased persistence of discrete bursts of instability above a critical value of the characteristic (Weissenberg no.) Wi; however, the onset value varies from pore to pore. This observation that single pores exposed to the same macroscopic flow rate become unstable in different ways provides a fascinating pore-scale analog of “molecular individualism” [P.  De Gennes, Molecular individualism. Science 276, 1999–2000 (1997)], in which single polymers exposed to the same extensional flow elongate in different ways; the authors therefore termed it “porous individualism”, although it is important to note that here, this effect is still at the continuum (not molecular) scale. Thus, unstable flow is spatially heterogeneous across the different pores of the medium, with unstable and laminar regions coexisting >>

AA << quantitatively established that the energy dissipated by unstable pore-scale fluctuations generates an anomalous increase in flow resistance through the entire medium that agrees well with macroscopic pressure drop measurements. >>

Sujit S. Datta, Arezoo M. Ardekani, et al. Perspectives on viscoelastic flow instabilities and elastic turbulence. arXiv: 2108.09841v1 [physics.flu-dyn]. Aug 22, 2021. 



keywords: gst, droplet, fluctuations, disorder, instability, viscoelastic flow instability, turbulence, elastic turbulence, individualism, porous individualism, transition