# gst: apropos of drift-waves, their coherent puff and slugs in transitional turbulence.

<< The long-term development of the transitional regime of drift-wave turbulence is studied in a magnetized plasma column by means of the conditional-average technique. >>

<< In the transitional regime, small changes in the magnetic-field strength as control parameter lead to large changes in the correlation times, indicating the existence of a critical point of an underlying nonequilibrium continuous phase transition. >>

<< This and the spatiotemporal dynamics shows similarities to puff splitting, slug-gap splitting, and puff jamming. >>️

P. Manz, S. Knauer, et al. Coherent puff and slugs in transitional drift-wave turbulence. Phys. Rev. E 111, 045203. April 8, 2025.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.111.045203

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

Keywords: gst, waves, drift-waves, turbulence, jamming, transition, puff splitting, slug-gap splitting, puff jamming 

# gst: experimental investigation of turbulence modulation by deformable bubbles

<< In this work (AA) experimentally investigate the turbulence modulation in the wake of deforming bubbles in homogeneous and isotropic turbulence, in the regime where the turbulence fluctuation is stronger than or comparable to the bubble rising velocity. >>

<< In a quiescent or weak turbulence, the wake has a persistent direction due to the buoyancy. In turbulence, however, (Their) results suggest that the decorrelation time for the slip velocity roughly equals the bubble-sized eddy turn over time. It suggests that, when turbulence becomes intense enough, the slip velocity changes its direction and magnitude so frequently that a wake barely has time to develop. >>

<< As a result, both the intensity and length of the wake are significantly modified. Nevertheless, with sufficient bubble Reynolds number, the wake, albeit limited, can still modulate surrounding turbulence. >>

<< The results suggest that the local turbulence is augmented by the bubble wake, and the amount of augmentation depends heavily on the bubble Reynolds number, the orientation of the bubble semimajor axis relative to the slip velocity, and the bubble deformation. >>️

Xu Xu, Shiyong Tan, et al. Experimental investigation of turbulence modulation by deformable bubbles. Phys. Rev. Fluids 10, 033605. March 31, 2025.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.10.033605

Also: bubble, disorder & fluctuations, turbulence, vortex, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, bubble, deformable bubbles, bubble wake, bubble-bubble interaction, disorder & fluctuations, turbulence, turbulence modulation, surrounding turbulence, vortex, slip velocity, buoyancy

# gst: switching from active Brownian motion to stationary rotation of Janus particles in a viscoelastic fluid.

<< Swimming micro-objects exist in viscoelastic fluids. Elucidating the effect of viscoelasticity on the motion of these objects is important for understanding their behavior. >>

AA << examined the motion of Janus particles self-propelled by induced charge electrophoresis over a wide range of speeds in semidilute polymer solutions. In (Their) system, the motion of Janus particles changed from active Brownian motion to stationary rotation as the speed increased. The torque for stationary rotation originates from the difference between the direction of self-propulsion and that of the time-delayed restoring force from the polymer solution, which has been reported in another self-propelled particle system. The switch from active Brownian motion to stationary rotation at different polymer concentrations can be explained by the Weisenberg number, which is defined as the ratio of the relaxation time of the polymer network to the travel time of the Janus particle to its size. >>

Keita Saito, Ryunosuke Kawano, et al. Self-propelled motion of induced-charge electrophoretic Janus particles in viscoelastic fluids. Phys. Rev. E 111, 045409. Apr 10, 2025.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.111.045409

️

Also: Janus, transition, particle, in FonT:

Janus https://flashontrack.blogspot.com/search?q=janus 

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

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

Keywords: gst, Janus, transitions, particles, self-propelled particles

# gst: chaotic and time-periodic edge states in square duct flow.

AA << analyse the dynamics within the stability boundary between laminar and turbulent square duct flow with the aid of an edge-tracking algorithm. As for the circular pipe, the edge state turns out to be a chaotic attractor within the edge if the flow is not constrained to a symmetric subspace. The chaotic edge state dynamics is characterised by a sequence of alternating quiescent phases and regularly occurring bursting episodes. These latter reflect the different stages of the well-known streak-vortex interaction in near-wall turbulence: the edge states feature most of the time a single streak with a number of flanking quasi-streamwise vortices attached to one of the four surrounding walls. The initially straight streak undergoes the classical linear instability and eventually breaks in an intense bursting event due to the action of the quasi-streamwise vortices. At the same time, the vortices give rise to a new generation of low-speed streaks at one of the neighbouring walls, thereby causing the turbulent activity to `switch' from one wall to the other. >>

<< When restricting the edge dynamics to a single or twofold mirror-symmetric subspace, on the other hand, the outlined bursting and wall-switching episodes become self-recurrent in time. These edge states thus represent the first periodic orbits found in the square duct. In contrast to the chaotic edge states in the non-symmetric case, the imposed symmetries enforce analogue bursting cycles to simultaneously appear at two parallel opposing walls in a mirror-symmetric configuration. Both localisation of the turbulent activity to one or two walls and wall switching are shown to be a common phenomenon in low Reynolds number duct turbulence. (They) therefore argue that the marginally turbulent trajectories transiently visit the identified edge states during these episodes, so that the edge states become actively involved in the turbulent dynamics. >>️

Markus Scherer, Markus Uhlmann, Genta Kawahara. Chaotic and time-periodic edge states in square duct flow. arXiv: 2503.22519v1 [physics.flu-dyn]. Mar 28, 2025️. 

https://arxiv.org/abs/2503.22519

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

Keywords: gst, turbulence, duct turbulence, chaos, chaotic edge states, vortex, instability, wall-switching episodes, bursting cycles 

# gst: apropos of odd droplets; fluids with broken symmetries could self-control their mechanics.

<< Flows with deformable interfaces are commonly controlled by applying an external field or modifying the boundaries that interact with the fluid, (..) Here, (AA) demonstrate that fluids with broken symmetries can self-control their mechanics. (They) demonstrate that odd viscosity dramatically disrupts conventional symmetric spreading by inducing asymmetric deformations and chiral flow patterns. (Their) analysis reveals a variety of dynamic regimes, including leftward and rightward bouncing, as well as rolling, depending on the relative strength of the odd viscosity. >>️

Hugo França, Maziyar Jalaal. Odd Droplets: Fluids with Odd Viscosity and Highly Deformable Interfaces. arXiv: 2503.21649v1 [cond-mat.soft]. Mar 27, 2025.

https://arxiv.org/abs/2503.21649

Also: drop, droplet, droploid, chiral, bouncing, rolling, slipping, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, drop, droplet, droploid, chirality, bouncing, rolling, slipping, oddity, odd viscosity, self-control

# gst: multiparticle dispersion in rotating-stratified turbulent flows (when stratification increases turbulent fluctuations may not be weaker)

AA << study the relative movement of groups of two (pairs) and four (tetrahedra) Lagrangian particles using direct numerical simulations of the stably stratified Boussinsesq equations, with Brunt-Väisälä frequency 𝑁 and Coriolis parameter 𝑓. >>

<< In all cases considered, (AA) demonstrate that the relative particle motion differs depending on whether dispersion is considered forward or backward in time, although the asymmetry becomes less pronounced when stratification and rotation increase. On the other hand, the strong fluctuations in the dispersion between two particles become more extreme when 𝑁 and 𝑓  increase. (They) also find evidence for the formation of shear layers, which become more pronounced as 𝑁 and 𝑓  become larger. Finally, (They) show that the irreversibility on the dispersion of a set of particles initially forming a regular tetrahedron becomes weaker when the influence of stratification and rotation increases, a property that (They) relate to that of the perceived rate-of-strain tensor. >>️

<< Unexpectedly, (AA) observe that the higher moments of particle separation, in particular the normalized fourth-order central moment of the separation (the kurtosis Kr) is an increasing function of stratification and rotation. This is surprising, as when stratification increases the turbulent fluctuations are expected to be weaker, (..) >>️

Sebastian Gallon, Fabio Feraco, et al. Multiparticle dispersion in rotating-stratified turbulent flows. Phys. Rev. Fluids 10, 034605. Mar 17, 2025. 

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.10.034605

Also: particle, turbulence, disorder & fluctuations, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, particle, turbulence, disorder, fluctuations

# gst: conventional and anomalous mobility edges in a quasiperiodic chain.

<< Mobility edges (MEs) constitute the energies separating the localized states from the extended ones in disordered systems. Going beyond this conventional definition, recent proposal suggests for an ME which separates the localized and multifractal states in certain quasiperiodic systems - dubbed as the anomalous mobility edges (AMEs). >>

<< In this study, (AA) propose an exactly solvable quasiperiodic system that hosts both the conventional and anomalous mobility edges under proper conditions. (They) show that with increase in quasiperiodic disorder strength, the system first undergoes a delocalization to localization transition through an ME of conventional type. >>

<< Surprisingly, with further increase in disorder, (They) obtain that a major fraction of the localized states at the middle of the spectrum turn multifractal in nature. Such unconventional behavior in the spectrum results in two AMEs, which continue to exist even for stronger quasiperiodic disorder. >>

AA << numerically obtain the signatures of the coexisting MEs complement it through analytical derivation using Avila's global theory. In the end (They) provide important signatures from the wavepacket dynamics. >>️

Sanchayan Banerjee, Soumya Ranjan Padhi, Tapan Mishra. Emergence of distinct exact mobility edges in a quasiperiodic chain. arXiv: 2503.19834v1 [cond-mat.quant-gas]. Mar 25, 2025.️

https://arxiv.org/abs/2503.19834

Also: edge, order, disorder, waves, transition,  in https://www.inkgmr.net/kwrds.html 

Keywords: gst, edge, order, disorder, waves, transition