Author: toschi

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/

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.

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

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/