Article
Physics, Fluids & Plasmas
Tobias Baetge, Michael Wilczek
Summary: The study focuses on the influence of small-scale mixing on large-scale dynamics, showing that small-scale averaging can effectively mimic the diffusivity of phenomenological eddy viscosity models and reduce the effective Reynolds number of the advecting velocity field. A filtering procedure has been established to accurately map second-order statistics of the fully resolved passive scalar field to the one obtained by small-scale averaging, capturing higher-order large-scale statistics of passive scalar fields.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Subharthi Chowdhuri, Giovanni Iacobello, Tirtha Banerjee
Summary: The study demonstrates that large-scale intermittency in convective surface layer turbulence is related to strong nonlinear dependencies in temperature signals, while similar phenomena are not observed in velocity signals. A competition between linear and nonlinear effects tends to inhibit temperature-like intermittency behavior in streamwise and vertical velocities. This suggests new research avenues may be opened up in studying large-scale intermittency in convective turbulence.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Multidisciplinary
Jose M. Angulo, Ana E. Madrid
Summary: Intermittency is a heterogeneous behavior that is of interest in various fields, such as system dynamics and risk assessment. Wavelets are useful for analyzing intermittency, especially when considering the effect of deformation on the energy transfer and the distribution of energy at different scales. This paper investigates the impact of deformation on intermittency indicators and evaluates the changes in generalized entropy and complexity measures.
Article
Materials Science, Multidisciplinary
Eduard A. Podshivaylov, Maria A. Kniazeva, Alexander O. Tarasevich, Ivan Yu. Eremchev, Andrei V. Naumov, Pavel A. Frantsuzov
Summary: Despite extensive research, the cause of the blinking phenomenon in single semiconductor colloidal quantum dots (QDs) is still not well understood. This study proposes an enhanced model that attributes the blinking to fluctuations in the rate of nonradiative relaxation due to temporal variations in the electron-phonon interaction coupling. The model successfully reproduces the results of spectroscopy experiments on single CdSeS/ZnS core/shell QDs. To analyze the temporal properties of blinking, a new method of power spectral density estimation based on the second-order cross-correlation function of the PL intensity is proposed, which extends the frequency range significantly.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Mechanics
Ron Shnapp
Summary: This study focuses on the intermittency in Lagrangian velocity statistics in canopy flows, observing non-Gaussian and not self-similar statistics at small scales and a dependence of energy increments on the direction of trajectories' time-averaged turbulent velocity. The results suggest similarities with homogeneous isotropic turbulence and the presence of large-scale intermittency in Lagrangian statistics in canopy flows.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Multidisciplinary Sciences
Alexei A. Mailybaev, Simon Thalabard
Summary: This article reveals a hidden scaling symmetry of the Navier-Stokes equations in the limit of vanishing viscosity. Through dynamical space-time rescaling, this symmetry projects solutions that differ only up to Galilean invariance and global temporal scaling onto the same representative flow. This symmetry statistically repairs the broken scale invariance caused by intermittency in the original formulation.
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2022)
Article
Mechanics
Amitesh Roy, Jason R. R. Picardo, Benjamin Emerson, Tim C. C. Lieuwen, R. I. Sujith
Summary: The inner intermittency of a premixed turbulent V-flame is experimentally revealed, which is distinct from the large-scale outer intermittency. The frequency spectrum of flame fluctuations follows a power-law distribution with an exponent close to -2, while the temporal increment of the flame position shows anomalous scaling. High-curvature, cusp-like structures on the flame surface are found to be responsible for the small-scale inner intermittency, which is important for modeling premixed turbulent flames.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Mathematical
Alexei A. A. Mailybaev, Artem Raibekas
Summary: This paper introduces a class of multi-scale systems with discrete time, which are motivated by the problem of inviscid limit in fluid dynamics in the presence of small-scale noise. These systems are infinite-dimensional and defined on a scale-invariant space-time lattice. The paper proposes a qualitative theory describing the vanishing regularization (inviscid) limit as an attractor of the renormalization group operator acting in the space of flow maps or respective probability kernels. The results are illustrated with solvable models: symbolic systems leading to digital turbulence and systems of expanding interacting phases.
COMMUNICATIONS IN MATHEMATICAL PHYSICS
(2023)
Article
Astronomy & Astrophysics
Tommaso Alberti, Davide Faranda, Reik Donner, Theophile Caby, Vincenzo Carbone, Giuseppe Consolini, Berengere Dubrulle, Sandro Vaienti
Summary: The study found that large-scale transitions in the solar wind magnetic field are induced by small-scale dynamics through an inverse cascade mechanism, while electron contributions may be hidden by instrumental noise.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Riccardo Uglietti, Daniele Micale, Damiano La Zara, Aristeidis Goulas, Luca Nardi, Mauro Bracconi, J. Ruud van Ommen, Matteo Maestri
Summary: This study demonstrates the potential of combining numerical and experimental approaches in understanding catalytic reactors, particularly fluidized beds. Through experiments and data analysis, the effectiveness of the in-house first-principles multiscale Computational Fluid Dynamic-Discrete Element Method (CFD-DEM) model is validated, and the fundamental insights that can be achieved through detailed numerical methods are reported. The integration of experimental information and numerical simulations allows for optimal design and scale-up procedures for reactor configurations with promising prospects in the energy transition.
REACTION CHEMISTRY & ENGINEERING
(2023)
Article
Neurosciences
Michael X. Cohen, Bernhard Englitz, Arthur S. C. Franca
Summary: Neural activity is coordinated across multiple spatial and temporal scales, with patterns of coordination implicated in both healthy and impaired cognitive operations. A constellation of multidimensional, inter-regional networks was identified, reproducible within animals across different recording sessions but varied across different animals. The theta band networks showed several prominent features, including equal contribution from all regions and strong inter-network synchronization.
Article
Mechanics
Alberto Vela-Martin
Summary: This work provides evidence of the relationship between intense events in the dissipative range of turbulence and the energy cascade. The study constructs signals using generalized means to track the temporal evolution of these events in isotropic turbulence simulations. The results show significant time correlation between these signals and the average dissipation signal, indicating the role of the energy cascade in driving intense events in the dissipative range.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Yann Carteret, Dominik Schleicher, Jennifer Schober
Summary: Fluctuation dynamos play an important role in amplifying and maintaining cosmic magnetic fields in turbulent plasmas in astrophysics. Analytical models, such as the Kazantsev model, have been developed to describe their behavior, but they rely on simplifying assumptions that may not hold in the interstellar medium. In this study, we use the renewing flow method to extend Kazantsev's results to a more general class of turbulent flows and investigate the effects of compressibility and finite correlation time.
Article
Mechanics
Yanguang Long, Jinjun Wang, Chong Pan
Summary: The study reveals the significant impact of large-scale motions on the turbulent/nonturbulent interface and turbulent entrainment in turbulent boundary layers. High-speed large-scale motions enhance the engulfment process and result in a more distorted TNTI. These mechanisms are universal for turbulent boundary layers with different wall shapes.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Subharthi Chowdhuri, Khaled Ghannam, Tirtha Banerjee
Summary: This study investigates the intermittent dynamics of momentum transport and its underlying time scales in the near-wall region of the atmospheric boundary layer, with a focus on the impact of a vegetation canopy. The results suggest that canopy-induced coherent structures have a significant influence on momentum transport, with long-lived events being responsible for the majority of momentum transport above the canopy.
JOURNAL OF FLUID MECHANICS
(2022)