Life in a Turbulent Environment

Life in a Turbulent Environment: How the Dynamic Ocean Shapes the Distribution, Diversity and Growth of Microorganisms 
Workshop at the Radcliffe Institute for Advanced Study at Harvard University, February 19-20, 2015
Link: http://projects.iq.harvard.edu/life_in_a_turbulent_environment

Executive Summary

This two-day workshop convenes expertise from the physical, biological and ocean sciences to stimulate a multidisciplinary discussion on how the dynamics of the ocean environment shapes life — ranging from individual plankton and microbes, to their collective ecosystems. How can we scale up our understanding from micro-environments to large-scale distributions, and from individual plankton to populations? How do the growth, transformation and transport of these populations therein affect the large-scale oceanic distributions of carbon, oxygen and nutrients? How does physical variability affect biological growth and patchiness, and how are physical and biological processes coupled through multiple space- and time-scales? From turbulence to ocean eddies — how does the dynamic ocean homogenize and differentiate environments to support growth? How do bio-diversity, species-composition, and size relate to the physical environment? And importantly, what changes can we anticipate in the evolution of planktonic and microbial marine ecosystems in the future? These are some of the questions that we will tackle through a series of talks and discussions in the convivial setting of the Radcliffe Institute at Harvard University.

Workshop Leaders

Amala Mahadevan

Homepage:  http://www.radcliffe.harvard.edu/people/amala-mahadevan

Federico Toschi

Homepage:  http://www.tue.nl/en/employee/ep/e/d/ep-uid/20089361/

David Nelson

Homepage:  https://www.physics.harvard.edu/people/facpages/nelson

Non-Spherical Particles and Aggregates in Fluid Flows

June 17, 2013 — June 21, 2013

Coordinators:
Cristian Marchioli (Università di Udine, Italy)
Federico Toschi (Eindhoven University of Technology, The Netherlands)

Dynamics of non-spherical particles and aggregates in fluid flow are encountered both in nature and in industrial applications. Examples for non-spherical particles include airborne solid particles or aerosols, carbon nanotubes, micro-organisms like phytoplankton, sediment-laden flows and wood-fibre suspensions. Particle aggregates are found in chemical, industrial or material processes for colloids and in polymer manufacturing. In these processes, particle size ranges from several nanometers to several centimeters, with loadings that may substantially change the macroscopic (rheological) properties of the suspension flow. On the other hand, transport and interaction of particles/aggregates in complex (e.g. turbulent) flows is governed by a number of physical processes occurring at a wide range of different scales. The rapidly increasing computational power has recently made feasible three-dimensional, time-dependent simulations of non-ideal particles in fluid flows, producing an entire branch of flourishing literature which is fostering research in dispersed multiphase flow. Progress has been substantial also from an experimental viewpoint, with improved measurement techniques based on optics or magnetic resonance flow imaging. Due to the multiscale nature of the problem, investigation and modelling require synergetic use of such approaches.
Objective of the course is to provide a general and unified frame of the current research on the dynamical behaviour of non-spherical particles and particle aggregates in complex flows and put future research paths in perspective. The focus will be on generic aspects and physics of non-ideal particle suspensions (e.g. rheological properties in suspensions of anisotropic deformable particles, and modulation of turbulence induced by particles/aggregates). Issues related to modelling and physical understanding at all various length scales will be covered: from the scale resolving the complex flow around individual non-spherical particles, to large eddy simulation models for flows with particles, to large-scale Eulerian-Eulerian models. Among the topics to be included are particle dynamics in free and wall-bounded turbulence, fluid-particle interactions, collision modelling, break-up and agglomeration, advances in measurement and simulation techniques, and rheological modelling.
The lectures will also provide a wide overview of cutting-edge work in this very active area of multiphase flow research and focus in more detail on a few advanced topics of significant practical and theoretical value in several areas of engineering and applied physics. This will reinforce understanding of the fundamental phenomena and their importance, providing participants with varied conceptual and methodological tools applicable to problems at hand. After the lectures, students should possess the necessary knowledge of the basic capabilities, potentials and limitations of the various numerical and experimental methods taught and, hence, should be able to critically evaluate the reliability and accuracy of the information these methods can provide when applied to practical situations.

Please register on the website

Particles in turbulence 2013

Please register on the website

July 1, 2013 — July 5, 2013

Prof. dr. Federico Toschi (Eindhoven University of Technology, Eindhoven)
Prof. dr. Eberhard Bodenschatz (Max Planck Institute for Dynamics and Self-Organization, Goettingen)

The transport, distribution and collisions of particles in turbulent flows is of fundamental interest, as well as being present in a variety of engineering and naturally occurring flows. Examples of related scientific challenges include rain formation in clouds, pollution dispersion in the atmosphere, emission reduction in combustion and plankton population dynamics. In such flows, particle inertia is an important parameter, but in many cases finite particle size and deformation play important roles. In most real life flows, the flow geometries are complex due to mixed forcing at various scales. This in addition to the complex relationship between large scale structures, intermittency and anisotropy at the small scales of motion in turbulence present us with a rare challenge increase the scope of our understanding, by systematically investigate complex flows from the numerical, theoretical and the experimental point of view.

The purpose of the conference is to bring together experts from various fields of turbulence research, exchange ideas and discuss new methodologies for addressing these challenging issues.

Please register on the website

Analysis, Modeling and Simulation of Collective Dynamics from Bacteria to Crowds 2012

Analysis, Modeling and Simulation of Collective Dynamics from Bacteria to Crowds

July 9, 2012 — July 13, 2012

Coordinators:

  • Federico Toschi (Eindhoven University of Technology, The Netherlands)
  • Adrian Muntean (Eindhoven University of Technology, The Netherlands)

The collective motion of individuals (correlated motion of ants or migration of bacteria, flocks of birds, just to mention but a few) is a fascinating phenomenon capturing our attention. Besides the aesthetic aspects induced by such an expression of collective behavior, there are many crucial aspects of practical nature that attracted the interest of various scientific communities ranging from logistics, theoretical biology, and ecology to statistical physics and mathematics. On one hand, we wish to better understand, for instance, the formation of swimming patterns in large communities of fish to improve large scale fishing strategies. On the other hand, in congested flows, pedestrians display significantly different behaviors from those typical to situations when they are walking in free conditions. If panic situations occur, then small microscopic (individual-level) interactions can lead to disastrous macroscopic patterns (e.g. shock-like waves) leading to the jamming of a desired evacuation option or even to losses of human lives.

The aim of this school is to present, by means of 6 mini-courses, the state-of-the-art of the theoretical (statistical mechanics and mathematics) understanding of collective motions of crowds. The topics we include here are:

• Kinetic models for self-organized collective motion.
• Discrete and continuum dynamics of reacting and interacting
individuals.
• Finite-speed propagation models of chemo-tactic movements.
• Modeling with measures:
(i) Multiscale modeling of pedestrian motions by time-evolving measures;
(ii) Motions and interactions in heterogeneous domains.
• Handling contacts in pedestrian dynamics: On the concept of pressure.

Multiscale models in social (networks) applications, eventually combining mean-field and kinetic equations with either microscopic or macroscopic objects, are approaches of strongly increasing importance and high potential for future quantitative research. Typically, individual-based models need to be intelligently coarse-grained to translate the relevant microstructure information to a mesoscopic (Boltzmann-level) or to a macroscopic (continuum) level.

Relevant questions include: What is the natural scaling for the averaging? How much microstructure information needs to be kept to capture the specific individual-level interaction responsible for the formation and propagation of the macroscopically-observed pattern (for instance, lane formation in pedestrian counterflow). What are the main microscopic interactions responsible for the macroscopic cross-diffusion transport mechanism sometimes arising in pedestrian’s motion?

Within the frame of this school, we emphasize on one hand the role played by measure theory in deriving averaged equations, while on the other hand we show how measure theory can be used to prove rigorously the mean-field derivation of chemo-tactic movements, e.g. Numerical simulations of generic collective motions as well as experimental findings and simulations of pedestrian flows hosting macroscopic patterns will be pointed out.

The target audience of this summer school are graduate students, PhD candidates and young faculty members in mathematics, applied theoretical physics and biology, as well as (chemical, transportation, mechanical, ...) engineering having a strong research interest in understanding the multiscale complexity of the collective motion behavior. The participants are expected to have a good mathematical background. We hope that everybody will be willing to actively participate in both discussion and poster sessions.
KEYWORDS: Lanes and Flocks Formation, Social and Behavioral Sciences, Conservation laws, Micro and Macro Models, Mass Measures, Averaging, Social Networks, Initial and Boundary Value Problems.

http://www.cism.it/courses/C1207/

Non ideal particles and aggregates in turbulence 2012

Suspensions of small aggregates are found in many different situations, such as environmental, chemical, industrial or material processes for colloids, polymer manufacturing and aerosols. The control of small aggregates size distribution is a key question for the theoretical investigation, and more importantly for the processing of the suspensions. In turbulent fluid flows, the existence of a stationary mass distribution of such small aggregates is crucially linked to the properties of the flow (magnitude of the shear, shear distribution etc..). However, the role which is played by the turbulence is still the matter of investigation and debate.
The goal of this workshop is to gather experts in colloidal and non ideal particles suspensions, together with specialists of turbulent transport, to discuss about particles dynamics and statistics, and about the way aggregates breakup and coalesce in turbulent flows.

Organising Committee:

Alessandra S. Lanotte
Cosimo Elefante
Giovanni Lella
Fabio Massimo Grasso
(CNR Istituto di Scienze dell’Atmosfera e del Clima)

Scientific Committee:

Luca Biferale (Dept. Physics, University of Tor Vergata, Rome, Italy)
Ulrike Feudel (Institut für Chemie und Biologie des Meeres, University of Oldenburg, Germany)
Alex Liberzon (School of Mechanical Engineering, Tel Aviv University, Israel)
Cristian Marchioli (Dipartimento di Energetica e Macchine-DIEM, University of Udine, Italy)
Federico Toschi (Technische Universiteit Eindhoven, The Netherlands)

Sponsored by:

MPNS COST Action MP0806 "Particles in Turbulence"
FPS COST Action FP1005 "Fibre suspension flow modelling"

http://frag2012.le.isac.cnr.it/

New Directions in Turbulence 2012

SCIENTIFIC CONTENT

This six-week program (12 March 2012 to 20 April 2012) will focus on recent development in the understanding of fluid dynamics turbulence with the goal to identify promising breakthrough directions.

From the point of view of theoretical physics, turbulence is a classical field theory, out of equilibrium and in a strong coupling  regime.

Turbulence is one of the great problems of classical physics still mainly unsolved. With turbulence we mean a physical state of a flow with many  dynamically active variables and far from equilibrium. The first  difficulty in theoretical approaches to turbulence consists in the large number of active degrees of freedoms. The scales where energy is  injected is typically  strongly separated from the scales where energy  is dissipated. Non-linear interactions lead to a strong coupling  between all degrees of freedoms. Energy transfer may be in average  positive, leading to formation of small-scales fluctuations superposed  to large scale structures or in average  negative, leading to  an  accumulation of energy at larger and larger scales. Moreover, fluctuations around the mean can be Gaussian or strongly intermittent, depending on the direction of the energy cascade and on the  dimensionality of the system.  The situation is complicated in  presence of active scalar fields, like for the case of thermal convection, active vector fields, as in magnetohydrodynamics and/or by  the presence of boundaries, where also a net transfer of momentum is established in the system. The Lagrangian point of view, measuring  underlying fluid velocity riding tracers or inertial particles,  point-like or with a finite size, is also crucial to control statistical properties at different frequencies.

Among the questions that will be address during the program we cite: is the energy cascade in isotropic turbulence  universal?  What are  the corrections expected in presence of large scale anisotropy? What  happens if external or internal mechanism breaks parity invariance?  What happens at changing the embedding dimensionality? Can we improve   sub grid modeling by a better understanding of the energy cascade mechanism? What are the effects of strong active fields, like in thermal  convection and MHD? Are large scale structures universal in these latter cases? What are the statistical connections between Eulerian  and Lagrangian descriptions. Can 2d and 3d physics coexist? Can we smoothly change from a 2d to a 3d systems?   What about turbulence in  1d turbulence (Burgers equations) in 0d (Shell Models) in larger and  larger dimension  or even in non-integer dimensions?

A partial answer to even only a small sub-set of these questions will require important synergies between scientists from theory, numerics and experiments and would qualify the program as big success.

The program will be organised in "focused" weeks concerning one or two of  the above topics.

TENTATIVE PROGRAM

12/03-18/03 : sub-grid modeling, wall bounded flows, Non Newtonian flows.

19/03-25/03 : 2d and 3d systems. Turbulence in rotating systems; Geophysical flows.

26/03-01/04 : Lagrangian and Eulerian turbulence.

02/04-06/04 : INTERNATIONAL CONFERENCE.

07/04-13/04 : Thermal convection & Magnetohydrodynamics.

14/04-20/04 : Turbulence modeling and theory.

Particles in Turbulence 2012

Aim & Description

The goal of the workshop is to bring together scientists working in the fundamental physics of particle transport in turbulence and related phenomena. The idea is to focus on a short but intense period (the workshop is organized over 3 full days) and to bring together scientists working on: experimental, numerical, theoretical as well as applied aspects.

The format is designed to allow exchange amongst scientists with different interests (plenary meetings, time for individual discussions amongst participants) as well as to stimulate technical discussions and collaborations (the four parallel working group, WGs, meetings). Exchange will further be stimulated by assembly, before the workshop, a list of topics and key themes to be discussed. During this workshop, this list will then be discussed from the point of view of experiments, numerical simulation, theory and applications.

There will be few keynote plenary lectures (including time for discussion) in order to provide an update on the state-of-the-art and on the outstanding open issues for each of the WGs themes. These lectures are expected to be tutorial-like and to be accessible to all attendees. The workshop is then composed by several slots during which the four WGs will convene in parallel sessions. Slots where WGs convene in a joint session are also scheduled and are believed to be the distinguish feature of this LC workshop. Large time is left for individual interaction amongst participants. On the last day there will be a discussion on what has been achieved during the week and outlook for the future activities, exchanges and challenges. Particular care will be devoted in choosing the chair for this last session. The scientific presentations will be made available on the MP0806 website. We plan to write a short document highlighting the research directions and collaboration possibilities that emerged during the workshop.

http://www.lorentzcenter.nl/lc/web/2012/488/description.php3?wsid=488

Particles in complex flows 2012

The transport, distribution and collisions of particles in turbulent flows is of fundamental interest, as well as being present in a variety of engineering and naturally occurring flows. Examples of related scientific challenges include rain formation in clouds, pollution dispersion in the atmosphere, emission reduction in combustion and plankton population dynamics. In such flows, particle inertia is an important parameter, but in many cases finite particle size and deformation play important roles. In most real life flows, the flow geometries are complex due to mixed forcing at various scales. This in addition to the complex relationship between large scale structures, intermittency and anisotropy at the small scales of motion in turbulence present us with a rare challenge increase the scope of our understanding, by systematically investigate complex flows from the numerical, theoretical and the experimental point of view.

http://mp0806.cineca.it/reykjavik/