Optimal tracking strategies in a turbulent flow in Communication Physics

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ISC researcher, M. Cencini  coauthored  an interesting work recently published in Communications Physics, C. Calascibetta, L.  Biferale, F. Borra, F.  and M. Cencini, Optimal tracking strategies in a turbulent flow,  Commun. Phys. 6, 256 (2023).

Abstract

Pursuing a drifting target in a turbulent flow is an extremely difficult task whenever the searcher has limited propulsion and maneuvering capabilities. Even in the case when the relative distance between pursuer and target stays below the turbulent dissipative scale, the chaotic nature of the trajectory of the target represents a formidable challenge.

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Heat flow on the nanoscale in La Rivista del Nuovo Cimento (2023)

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ISC researcher Stefano Lepri and ISC associate Roberto Livi coauthored an interesting review article  showing how heat flow is different on the nanoscale.

G. Benenti, D. Donadio, S. Lepri and R. Livi, Non Fourier heat transport in nanosystems, La Rivista del Nuovo Cimento (2023)

Energy transfer in small nano-sized systems can be very different from that in their macroscopic counterparts due to reduced dimensionality, interaction with surfaces, disorder, and large fluctuations.

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Epidemic spreading under mutually independent intra- and inter- host pathogen evolution – Nature Communications

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Stefano Boccaletti, researcher @ ISC – Firenze, coauthored an interesting work discussing how evolving pathogens impact the reproduction number and macroscopic dynamics of spreading processes. The article is also featured in  the Applied Physics and Mathematics Focus page selecting “the most interesting papers published in Nature Communications in the interdisciplinary areas where diverse approaches at the boundaries of physics, mathematics, materials science and engineering take place to create new research opportunities”

Epidemic spreading under mutually independent intra- and inter-host pathogen evolution, X.… Read the rest

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Chaos, Solitons and Fractals ranked 1 out of 108 in Mathematics, Interdisciplinary Applications by Clarivate.

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The 2021 Impact Factor of Elsevier’s Chaos, Solitons and Fractals: the interdisciplinary journal of Nonlinear Science, and Nonequilibrium and Complex Phenomena  is 9.922, ranking it 1 out of 108 in Mathematics, Interdisciplinary Applications.

ISC researchers strongly contributed to the success of Chaos, Solitons and Fractals, as Editors as well as Authors through publications of high scientific value.  Congratulations to ISC researchers Stefano Lepri and Stefano Boccaletti who have been respectively Editor and Chief Editor of this journal for many years.

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A Random Walk in Physics – Book

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A Random Walk in Physics: Beyond Black Holes and Time-Travels is a book by
Massimo Cencini, Andrea Puglisi, Davide Vergni and Angelo Vulpiani.

Read a review in italian at Galileo… Read the rest

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Coexistence of Plasmoid and Kelvin–Helmholtz Instabilities in Collisionless Plasma Turbulence published in Astrophysical Journal April 2022

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ISC researchers Dario Borgogno e Daniela Grasso have  recently published the following interesting work,
Abstract
The plasmoid formation in collisionless plasmas, where magnetic reconnection within turbulence may take place
driven by the electron inertia, is analyzed. We find a complex situation in which, due to the presence of strong
velocity shears, the typical plasmoid formation, observed to influence the energy cascade in the
magnetohydrodynamic context, has to coexist with the Kelvin–Helmholtz (KH) instability.
… Read the rest
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Nature Reviews: The physics of financial networks

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ISC associates Guido Caldarelli  and Gulio Cimini coauthored an interesting review on modelling the financial systems and networks now published in Nature Reviews, M. Bardoscia, P. Barucca, S. Battiston, F. Caccioli, G. Cimini, D. Galaschelli, F. Saracco, T. Squartini, and G. Caldarelli. Nat. Rev. Phys. June (2021).

As the total value of the global financial market outgrew the value of the real economy, financial institutions created a global web of interactions that embodies systemic risks.… Read the rest

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Nature Communications: Stochastic sampling effects favor manual over digital contact tracing

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ISC researcher Claudio Castellano and collaborators unveil the roles of contact tracing procedures in mitigating COVID-19 pandemic, now published in Nature Communications, see M. Mancasroppa, C. Castellano, A. Vezzani and R. Burioni, Stochastic sampling effects favor manual over digital contact tracing, Nature Communications 12, 1919 (2021).

 

Abstract

Isolation of symptomatic individuals, tracing and testing of their nonsymptomatic contacts are fundamental strategies for mitigating the current COVID-19 pandemic.… Read the rest

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Analytical Model for Particle Capture in Nanopores, ACS Nano (2020)

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Our researcher, Fabio Cecconi, has developed an analytical model elucidating the competition among electrophoresis, electroosmosis, and dielectrophoresis. The work is published on ACS Nano, M. Chinappi, Misa Yamaji, Ryuji Kawano, and Fabio Cecconi, “Analytical Model for Particle Capture in Nanopores Elucidates Competition among Electrophoresis, Electroosmosis, and Dielectrophoresis” ACS Nano, 14, 15816 (2020).

 

Abstract

The interaction between nanoparticles dispersed in a fluid and nanopores is governed by the interplay of hydrodynamical, electrical, and chemical effects.… Read the rest

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k-statistics approach to epidemiology – Scientific Reports

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Antonio Maria Scarfone and co-authors have published The k-statistics approach to epidemiology in Scientific Reports 10, Article number: 19949 (2020)
G. Kaniadakis, M.M. Baldi, T.S. Deisboeck, G.Grisolia, D.T. Hristopulos, A.M. Scarfone, A. Sparavigna, T. Wada, U. Lucia
Keywords: Plague, Pandemics, Epidemics, -Statistics; -deformed Weibull; survival function

Abstract

A great variety of complex physical, natural and artificial systems are governed by statistical distributions, which often follow a standard exponential function in the bulk, while their tail obeys the Pareto power law.… Read the rest

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Communicating sentiment and outlook reverses inaction against collective risks – pnas

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Zhen Wang, Marko Jusup, Hao Guo,Lei Shi, Sunčana Geček, Madhur Anand, Matjaž Perc, Chris T. Bauch, Jürgen Kurths, Stefano Boccaletti, and Hans Joachim Schellnhuber have published
Communicating sentiment and outlook reverses inaction against collective risks

Collective risks trigger social dilemmas that require balancing selfish interests and common good. One important example is mitigating climate change, wherein without sufficient investments, worldwide negative consequences become increasingly likely.… Read the rest

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Cumulative Merging Percolation and the Epidemic Transition of the Susceptible-Infected-Susceptible Model in Networks

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Claudio Castellano and Romualdo Pastor-Satorras published this article in Phys. Rev. X 10, 011070 – Published 24 March 2020

Complex networks represent the interaction pattern for many real-world phenomena such as epidemic spreading. The simplest and most fundamental model for the diffusion of infectious diseases without acquired immunity predicts a vanishing epidemic threshold in the limit of large systems. In other words, no matter how small the infectiousness of the disease, there is always a finite fraction of the overall population which is infected for long times.… Read the rest

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Alignment of Nonspherical Active Particles in Chaotic Flows – Physical Review Letters

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Massimo Cencini has published Alignment of Nonspherical Active Particles in Chaotic Flows in Physical Review Letters.

Active particles, such as motile microorganisms or artificial microswimmers, swim in a surrounding flow, either externally imposed or self-generated. Besides transporting the active particles, the flow velocity change their swimming direction by exerting a shape-dependent torque through the velocity gradients. The complex interplay of flow advection, particle orientation and self-propulsion is fundamental to understand key processes at the crossroad between aquatic ecology, active matter modeling, and nano/micro- technology with application to drug delivery.… Read the rest

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Optical networks as complex lasers

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A review article in the physics-central, physics-buzz blog has appeared presenting the recent results of G. Giacomelli, S. Lepri (ISC) and C.Trono (IFAC) about the LANER (lasing network):

http://physicsbuzz.physicscentral.com/2019/02/meet-laner-network-laser.html
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.99.023841… Read the rest

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Andrea Cavagna wins ERC Advanced Grant

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Congratulations to Andrea Cavagna for winning an ERC Advanced Grant (panel PE2) with the project:
Renormalization group approach to the collective behaviour of strongly correlated biological systems (RG.BIO)

Biological systems displaying collective behaviour are characterized by strong spatio-temporal correlations, which partly transcend the multiform diversity of their microscopic details, much as it happens in statistical physics systems close to a critical point.… Read the rest

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NAR: Energetic funnel facilitates facilitated diffusion

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Massimo Cencini has published Energetic funnel facilitates facilitated diffusion in Nucleic Acid Research.

Gene transcription is regulated by proteins – Transcription Factors (TFs) – that by binding to short target sequences are able to promote or impede the binding of RNA-Polymerase (RNAP) and, consequently, activate or repress tran-
scription. Fast and accurate control of gene expression is crucial for many biological functions, and relies on the ability of TFs to rapidly find their transcription factor binding site (TFBS) among a multitude of competing DNA sequences,
and to establish with it a stable complex.… Read the rest

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PRX: Relating Topological Determinants of Complex Networks to Their Spectral Properties: Structural and Dynamical Effects

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Claudio Castellano has published Relating Topological Determinants of Complex Networks to Their Spectral Properties: Structural and Dynamical Effects in Physical Review X.

In many social and biological systems, the pattern of interactions is described by complex networks—mathematical constructions composed of points (vertices) representing individuals, joined by lines (edges), standing for pairwise interactions between them. These structures are important because they affect the behavior of the dynamical processes they mediate.… Read the rest

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Nonequilibrium statistical physics: A modern perspective (book)

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Paolo Politi and Roberto Livi have published a book:
Nonequilibrium statistical physics: A modern perspective.
Statistical mechanics has been proven to be successful at describing physical systems at thermodynamic equilibrium. Since most natural phenomena occur in nonequilibrium conditions, the present challenge is to find suitable physical approaches for such conditions: this book provides a pedagogical pathway that explores various perspectives.… Read the rest

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EPL Editor’s Choice: Effective mobility and diffusivity in coarsening processes

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Congratulations to Paolo Politi whose letter Effective mobility and diffusivity in coarsening processes has been selected as editor’s choice in Europhysics Letters.… Read the rest

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Economic Fitness: Evolving Economic Complexity for Development

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See also A Better Way to Make Economic Forecasts

Il 14 settembre alla Banca Mondiale di Washington
Questo evento è totalmente dedicato ai risultati e alle prospettive della collaborazione
tra il gruppo della Sapienza (Fisica) e dell’Istituto dei Sistemi Complessi del CNR,
coordinato dal Prof. Luciano Pietronero, con la World Bank.
Economic Fitness (EF) consiste in un nuovo paradigma sviluppato dal gruppo di
Pietronero in cui si descrivono le economie come processi evolutivi di ecosistemi di
tecnologie e infrastrutture industriali e finanziarie che sono globalmente
interconnesse.… Read the rest

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Dynamic scaling in natural swarms – Nature Physics

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Andrea Cavagna, Daniele Conti, Chiara Creato, Lorenzo Del Castello, Irene Giardina, Tomas S. Grigera, Stefania Melillo, Leonardo Parisi & Massimiliano Viale have published an article on the collective behaviour in biological systems which presents theoretical challenges beyond the borders of classical statistical physics.… Read the rest

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The LANER: optical networks as complex lasers

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Complex Active Optical Networks as a New Laser Concept by Stefano Lepri, Cosimo Trono and Giovanni Giacomelli has been published in Physical Review Letters.

The introduction of one or more active sections in a complex network may lead to laser emission. We call this system LANER (lasing network). As in the usual laser, when the gains are sufficiently high coherent emission is produced; in this case, the full network becomes a complicated, multipath and multigain cavity for the optical field.… Read the rest

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Meccanica statistica di non equilibrio

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Meccanica statistica di non equilibrio: trasporto e diffusione in sistemi complessi

Relatore: Stefano Lepri

Gli argomenti di tesi sono di tipo teorico e riguardano il comportamento di sistemi fuori equilibrio. Una preparazione di base in meccanica statistica e’ essenziale. La conoscenza di un linguaggio di programmazione per lo sviluppo di codici di simulazione e’ auspicabile.

 

Diffusione anomala

Il moto di una particella soggetta a forze aleatorie e’ descritto dalle leggi del moto browniano (diffusione).… Read the rest

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Forthcoming book on Nonequilibrium Statistical Physics

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Roberto Livi and Paolo Politi
Nonequilibrium Statistical Physics – A modern perspective
(Cambridge University Press, 2017)

 

Statistical mechanics has been proven to be successful at describing physical systems at thermodynamic equilibrium.  Since most natural phenomena occur in nonequilibrium conditions, the present challenge is to find suitable physical approaches for such conditions: this book provides a pedagogical pathway that explores various perspectives.… Read the rest

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Review on Spatio-temporal phenomena in complex systems with time delays

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Serhiy Yanchuk and Giovanni Giacomelli published a topical review in Journal of Physics A: Mathematical and Theoretical.

Real-world systems can be strongly influenced by time delays occurring in self-coupling interactions, due to unavoidable finite signal propagation velocities. When the delays become significantly long, complicated high-dimensional phenomena appear and a simple extension of the methods employed in low-dimensional dynamical systems is not feasible.… Read the rest

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Rules and Exceptions in Language Dynamics

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In all languages, rules have exceptions in the form of irregularities. Since rules make a language efficient, the persistence of irregularity is an anomaly. How language systems become rule governed, how and why they sustain exceptions to rules? Frequent words are unlikely to change over time (e.g., frequent verbs tend to maintain an irregular past tense form). What is the role of frequency in maintaining exceptions to rules?… Read the rest

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Mixing by degree in signed social networks

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Social networks have empirically been found to be assortative (i.e., the degree of neighboring nodes are positively correlated), while other networks (e.g., technological, biological) show the opposite pattern (disassortative). Why is that so?
How do these patterns change in signed networks, where relations indicate trust/distrust, friendship/enmity? Do individuals who dislike many others tend to dislike each other, or do they dislike those who dislike only very few others?… Read the rest

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Fractures and crack propagation

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The intermittent and self-similar fluctuations displayed by a slow crack during the propagation in a heterogeneous medium can be quantitatively described by an extension of a classical statistical model for fracture. The model yields the correct dynamical and morphological scaling, and allows to demonstrate that the scale invariance originates from the presence of a non-equilibrium, reversible, critical transition which, in the presence of dissipation, gives rise to self-organized critical behaviour.… Read the rest

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Synchronization of extended systems

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Synchronization is a long known phenomenon dating back to Huygens experiments who observed that suspending two pendula “…in the same wooden beam, the motions of each pendulum in opposite swings were so much in agreement that they never receded the least bit from each other and the sound of each was always heard simultaneously“. In spite of the early discovery, the phenomenon was fully understood much later with the experiments and theoretical analysis of E.… Read the rest

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Statistical physics modeling of social dynamics

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In recent years it has become widely recognized that many large-scale phenomena observed in social systems are the “macroscopic” complex effect of the “microscopic” simple behavior of a large number of interacting agents. This has led social scientists to the introduction of elementary models of social behavior (cellular automata, agent-based models). Many of these models are somehow relatives of models that have been introduced in modern traditional statistical physics, and it is natural to approach them using the same concepts and tools that have been successfully applied in physics.… Read the rest

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Regularities and universality in large-scale social phenomena

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In social phenomena every individual interacts with a limited number of peers, usually negligible as compared with the total number of people in the system. In spite of that, human societies are characterized by stunning global regularities. There are transitions from disorder to order, like the spontaneous emergence of a common language/culture or the creation of consensus about a specific topic.… Read the rest

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Fractal analysis of planetary topographies

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There exists an overwhelming diversity of landscapes on Earth. A cornerstone of modern geomorphology came with the realization that all the different features of the terrestrial surface result from the accumulated effect of current geological agents [Lyell, 1830]. This principle established for the first time a qualitative relationship between pattern and process in geology.
More than one century later, fractal geometry gave a theoretical framework able to provide quantitative measures for the patterns of landscapes, which were identified in a first approximation as self-similar, and triggered the research on mechanistic and theoretical models to identify the underlying constructive rules responsible for their appearance.… Read the rest

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GZIP: Galaxy morphology classification by zip algorithm

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Even before the identification of galaxies as stellar systems, astronomers have classified them based on their visual appearance. Galaxies in the local universe can organized in a sequence of morphologies (e.g. the Hubble sequence) which must be the result of the specific processes that originated them.
The relative roles over cosmic time of processes such as the merging of dark matter haloes, dissipation, starburst, feedback, active galactic nuclei (AGN) activity, etc.,… Read the rest

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Tidal tail characterization

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Introduction

A globular cluster (GC) is a spherical collection of stars that orbits a galactic core as a satellite.
Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is derived from the Latin globulus—a small sphere. Globular clusters are fairly common; there are about 158 currently known globular clusters in the Milky Way, with perhaps 10–20 more undiscovered.… Read the rest

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Spatially correlated random walks and turbulence

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The wide applicability of the random walks (RW) to natural phenomena relies just on the possibility to introduce appropriate generalizations on the probabilistic nature of displacements. A straightforward generalization is realized by assuming correlations in displacements to obtain the so called correlated random walks (CRW).

This possibility extends also to a set of particles distributed in space leading to the definition of spatially correlated random walks.… Read the rest

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Dynamics of self-gravitating systems

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A System with long-range interactions is characterized by an inter-particle potential which decays at large distances with a power law exponent which is smaller than the dimension of the embedding space. Classical examples include for instance: self-gravitating systems, unscreened Coulomb systems, ion beams, wave-particle systems of relevance to plasma physics and others.

The behaviour of the above mentioned systems is interesting both from the point of view of stable (or metastable) states, because equilibrium statistical mechanics shows new types of phase transitions and cases of ensemble inequivalence, and from the dynamical point of view, because they display peculiar fast relaxation followed by the formation of quasi-stationary states that are related to the underlying Vlasov-like equation.… Read the rest

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Matter density fields in the early universe

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The most prominent feature of the initial conditions of the matter spatial distribution in the early universe, in standard theoretical models, derived from inflationary mechanisms, is that matter density field presents on large scale super-homogeneous features. This means the following. If one considers the paradigm of uniform distributions, the Poisson process where particles are placed completely randomly in space, the mass fluctuations in a sphere of radius R growths as the volume of the sphere.… Read the rest

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Total gravitational force and the classification of long range interactions

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In equilibrium statistical mechanics the distinction between short and long range interactions is given by the integrability or not of the pair potential. However for what concerns only the clustering dynamics of a particle distribution under the effect of an attractive pair interaction, it seems by recent works that the distinction is given by the integrability of the pair force instead of the potential.… Read the rest

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Role of microscopic chaos to macroscopic transport

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The discovery that simple deterministic nonlinear systems could display dynamical evolution characterized by a randomness similar to stochastic processes changed very much researchers’ attitude toward determinism and predictability of natural phenomena. Determinstic chaos has been successfully invoked to interpret several irregular behaviors, however its role to the fundaments of statistical physics still remains debated in modern statistical mechanics. In other terms, one is tempted to think that a macroscopic system with chaotic microscopic interactions is more robust with respect to statistical mechanical principles thant the same system with non-chaotic interactions.… Read the rest

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Disorder driven non-equilibrium phase transition: the Random field Ising model

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In hard magnetic materials, the domain walls movement or even creation is suppressed, and other mechanisms, like domains nucleation and coherent spin rotation enter in the process of magnetization reversal. For these kind of materials a description in terms of spin models is more appropriate. We focused on the non-equilibrium properties of the random field Ising model (RFIM), to describe the competition between quenched disorder and exchange interactions and their effect on the hysteretic behavior.… Read the rest

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Systems with multiplicative noise

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Problems susceptible to be mathematically represented by stochastic Langevin equations including a multiplicative noise abound not only in physics, but also in biology, ecology, economy, or social sciences. In a broad sense a Langevin equation is said to be multiplicative if the noise amplitude depends on the state variables themselves. In this sense, problems exhibiting absorbing states, i.e. fluctuation-less states in which the system can be trapped, are described by equations whose noise amplitude is proportional to the square-root of the (space and time dependent) activity density, vanishing at the absorbing state.… Read the rest

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Metastable states and supersymmetry

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Both the static and the dynamical behaviour occurring in mean field spin glass models models can be interpreted as consequences of the complex (free) energy landscape that spin glasses have, with many minima, valleys and saddles. Traditionally, much attention has been devoted in the past to the analysis of absolute minima, i.e. equilibrium states. More recently, we have understood that also metastable states, i.e.… Read the rest

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Field theory for finite dimensional spin glasses

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Many features predicted by mean field spin glass models, such as the behaviour of susceptibilities and correlation functions or the occurrence of aging and off-equilibrium dynamics, are qualitatively observed in experiments, suggesting that the mean field scenario may hold for finite dimensional systems also. To investigate this hypothesis a field theory for the fluctuations around the mean field solution has been developed.… Read the rest

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The growth of amorphous order in supercooled liquids

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Close to the glass transition supercooled liquids display an impressive increase of the relaxation time, without any clear sign of growing thermodynamic order, nor correlation length. This is at variance with physical intuition, which suggests that a large relaxation time is always associated to a large correlation length. Even though dynamical length scales were introduced and measured, nothing similar was thought to be possible for thermodynamic lengths.… Read the rest

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Crackling noise: the Barkhausen effect

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The term “crackling noise” refers to the signal that some disordered systems produce as a response to an external driving field smoothly changing in time. Due to the presence of disorder, crackling signals are extremely irregular, despite the steady increase of the external forcing. They are typically characterized by a sequence of pulses of very different sizes and durations, separated by quiescence intervals.… Read the rest

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Dynamic hysteresis in thin and ultra-thin films

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The physics of thin and ultra-thin magnetic films has been extensively studied in the recent past, because of its important implications for applications to high frequency devices. Power losses in ferromagnetic materials generally depend on the frequency of the applied field, a phenomenon referred to as dynamic hysteresis. The problem has great importance from a purely theoretical point of view, for the understanding of the dynamics of disordered magnetic systems, which represents a central issue in non–equilibrium statistical mechanics.… Read the rest

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Dynamical Processes on Networks

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During the last decade it has become clear that the topology in many systems, ranging from technological to social to biological, is not well described by regular lattices nor by random graphs. Complex networks, characterized by small-world effects, large connectivity fluctuations, clustering, correlations and other nontrivial features are often a better description of many natural and man-made systems. Since many of such networks describe the topological patterns that mediate various sorts of interactions among nodes, it is natural and interesting to wonder what is the effect of complex topologies on dynamical processes taking place on them.… Read the rest

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Human Dynamics

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Until now, the study of human dynamics has been done only qualitatively. Actually, the present possibility to have quantitative data on the kind and nature of social relationships through social networks is driving a rapid change in the field. Thanks to the emergence of detailed datasets that capture human behavior, we can now follow specific human actions in ultimate detail. One of the first measurable quantity with which one can describe the relationship between humans is the timing and order with which we perform specific tasks.… Read the rest

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Random Lasers

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In a nutshell, a random laser is the coherent emission from active stochastic resonators.

In a series of articles around 1966, a Russian scientist V. S. Letokhov, of the Lebedev Physics Institute in Dubna considered the generation of light in the interstellar medium. In the presence of scatterers, as for example dust particles, photons diffuse like neutrons and, if some mechanism (following Letokhov a “negative absorption”) is able to increase their number, a sort of photonic reactor can be realized.… Read the rest

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Spin Glasses: a brief introduction

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Spin Glasses are dilute magnetic alloys where the interactions between spins are randomly ferromagnetic or anti-ferromagnetic, and are considered as paradigmatic examples of frozen disorder. The presence of disorder (the random interactions) induces frustration and a greater difficulty for the system to find optimal configurations. As a consequence, these systems exhibit non trivial thermodynamic and dynamic properties, different and richer than those observed in their non disordered counterpart.… Read the rest

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What is Econophysics?

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Collective phenomena in economics, social sciences and ecology are very attractive for statistical physicists, especially in view of the empirical abundance of non-trivial fluctuation patterns and statistical regularities — think of returns in financial markets or of allometric scaling in ecosystems — which pose intriguing theoretical challenges. On an abstract level, the problems at stake are indeed not too different from, say, understanding how spontaneous magnetization may arise in a magnetic system, since what one wants in both cases is to understand how the effects of interactions at the microscopic scale can build up to the macroscopic scale.… Read the rest

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Scale-free networks

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Scale-Free Networks are present in a wide list of phenomena. Examples range from the structure of the Internet and that of the WWW (we shall see in the following that they are different systems) to the interconnections between financial agents or species predation in ecological food webs. Thanks to the simplicity of graph theory it is very easy to provide a network description for different systems.… Read the rest

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Transport in binary mixtures

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When a binary fluid mixture at the critical concentration is cooled from a high temperature to a sufficiently low temperature (below a critical one), the original homogeneous phase becomes unstable and spontaneously evolves into two phases separated by an interface. As time advances, an out-of-equilibrium process of phase ordering takes place through the formation of domains of a single phase that grows algebraically in time as L(t)~t1/3.… Read the rest

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Lagrangian Turbulence

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Recently, part of the research activity on turbulence has focused on temporal properties of turbulent statistics which are much less known than the equivalent spatial properties, and are expected to bring information on some of the mechanisms responsible for intermittency in turbulence, for example lagrangian motion is strongly affected by the presence of vortical motion around vortex filaments (see Figure 1).… Read the rest

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Scalar Turbulence

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The ability of efficiently mixing transported substances is one of the most distinctive properties of turbulence. For instance, it is turbulence (induced by the spoon) that allows cream to rapidly invade a cup of coffee, indeed if only molecular diffusion would be at play in the coffee at rest the same process would require many hours! Given the statistical complexity of a turbulent velocity field, it is natural to wonder about the resulting complexity in the statistical features of the transported concentration field of a substance (e.g.… Read the rest

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Inertial Particles in Turbulent Flows

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We already mentioned that enhanced mixing is probably one of the most distinguishing feature of turbulence. When a turbulent flow is seeded with particulate matter having a finite size and/or density different from that of the carrier fluid, new features appear. The figure on the left show the instantaneous position particles which are heavier (e.g. water drops in air) resp. lighter (e.g.… Read the rest

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