Collective Dynamics of Particles: from Viscous to Turbulent Flows

May 26 - May 30 2014

Venue: CISM, Palazzo del Torso, Piazza Garibaldi 18, 33100 Udine

Course description

Rationale - The course delivers a comprehensive overview of particulate flows, from low Re numbers to full turbulent flows, and hence will be particularly attractive to graduate students,PhD candidates, young researchers and faculty members in applied physics and chemical-mechanical engineering. The advanced topics, and the presentation of the current progress in this very active field will also be of considerable interest to many senior researchers, as well as industrial practitioners having a strong interest in understanding the multi-scale complex behavior of such multiphase flows.Workshop sessions on Tuesday will be chaired by Cristian Marchioli (U. Udine).

The course is organised underthe auspices of ERCOFTAC and with the support of COST, through Action FP1005 "Fibre suspension flow modelling" and ANR CoDSPit "Collective dynamics of settling particles in turbulence"

 Scope- Particulate flows are present in many natural and industrial processes. Transport of sediment in rivers and estuaries, convection of pollutants in the atmosphere, biconvection of zooplankton, gravity and turbidity currents near coastal shore, pyroclastic flows from volcanic eruptions are a few examples that can be encountered in natural phenomena. In industry, processes involving flows of particles are numerous: among others, fluidized bed reactors, the treatment of waste materials in clarifiers, food processing, and ink technologies. In all the above-mentioned instances,proper understanding and accurate modelling of such complex flows are crucial aspects from scientific and engineering perspectives, as they directly impact the environment we live in.

The understanding of such flows is a duanting task for several reasons. The most straightforward is the very large number of particles one needs to account for. Another , equally significant difficulty arises from the subtle coupling between particle-particle and particle-fluid interactions: particle have an effect of the fluid flow (and sometimes even drive it) by exerting stresses on the fluid around them, and in turn the fluid flow modifies the motion of the suspended particles. This two-way coupling often makes attempts at comprehending such flows highly difficult, other than in very simplified settings.

Particulate flows have been examined in the past in a wide variety of situations. A very large number of studies have focused on highly viscous flows in which inertial forces can be neglected. This low-Reynolds-number limit is a valid approximation in small-scale systems or very slow flows, and is often justified when the size of the particles involved in the process is small. In many practical applications, however, fluid inertia cannot be neglected  owing the large system sizes, even when the suspended particles are small. In some cases, it is of fundamental importance such as in pyroclastic flows or in fluidized bed reactors where the flows are highly turbulent in spite of the microscopic size of the particles involved. Several studies have focused on the Lagrangian properties of particles in turbulence (e.g. Lagrangian acceleration) to gain further insight on the relevant forces acting on isolated particles.

Preferential concentration and clustering effect of inertial particles in a turbulent flow have been also examined in many recent works. However, collective effects in turbulent particle laden flows have been not thoroughly examined and there is a compelling need to provide a robust body of knowledge in this active field of research.

The scope of the course is therefore to provide a state-of-the-art and accessible survey of numerical and experimental approaches as well as modelling tools for the analysis of collective dynamics of particles in flows. The general approach will be made specific through the most tractable analytically case of low-Reynolds flows but will go beyond viscous flows and will tackle inertial and turbulent flows. The course will also cover the two basic avenues for addressing particulate flows, one being discrete particle simulations and the second being continuum two-phase modelling. In the later , the influence of particles is captured through constitutive relations often resulting from simulations or experiments. The most common discrete methods for the description of particle-laden lows, both in the Stokes regime and in the inertial and turbulent regimes, will be presented and discussed. Among the topics to be included are finite-size particles , deformable particles and particles of different shape, in particular, rod-like particles or fibres whose interest lies in part in the availability of methods for slender bodies as well as in their importance in industrial applications, such as the fabrication of fibre-reinforced materials of pulp and paper.


 Gilles BOUCHET  - Aix -Marseille University, CNRS (FRANCE)
 Michael BOURGOIN- Uni.  of Grenoble, CNRS (FRANCE)
 Jason BUTLER  - Uni. of Florida (USA)
 Holgert HOMANN - Observatoire de la Côte d’Azur, Nice (FRANCE)
 John HINCH  - University of Cambridge (UK)
 Martin MAXEY - Brown University (USA)

Course homepage:

Registration :

Travel - How to reach Udine

Udine is situated in the North Eastern part of Italy, about 90 km from Austria and 40 km from Slovenia.

By plane
There are three main airports serving the North East of Italy:
– Venezia (Marco Polo airport)
– Trieste (Ronchi dei Legionari airport)
– Treviso (Antonio Canova airport).

The best international connections are through Venice airport “Marco Polo” (IATA code VCE).
From this airport you may easily reach Udine by train using the close railway station of Mestre. Mestre railway station is connected by bus to the Marco Polo airport (ask for the bus to Mestre, not to Venezia, piazzale Roma). There are two bus services:
1. ATVO Fly Bus ( runs daily, every 20 minutes approximately. Journey time is 20 minutes. Tickets may be purchased inside the arrival hall at the ATVO box, € 5,00 luggage included.
2. ACTV (town transport service, bus number 15 – orange): runs daily, every 30 minutes. Journey time is 25-30 minutes approximately. Tickets: inside the arrivals hall, € 1,30 luggage not included. Both ACTV and ATVO lines also provide bus service to Venezia (piazzale Roma). From Mestre railway station there are several trains to Udine, on the line Venezia-Vienna. Trains run almost every hour: . Some require supplements or seat reservation. The journey takes about 2 hours.

For more information on Venice airport and connecting services check:

For train connections:

The nearest airport to Udine is at Ronchi dei Legionari also known as Trieste airport (IATA code TRS). Routing is mainly through Milano and Roma.
From this airport there is a bus service to/from Udine run by APT Gorizia (line number 51). Schedules and fares are available at APT Gorizia ( or calling the bus operator (+39–0481–593511). Arrival in Udine is at the central bus station, in front of the railway station. Journey time is approximately 45 minutes. Tickets can be purchased at the airport in the arrivals hall, with an automatic machine for self-ticketing and at Tourist Information Counter (Turismo FVG). Leaving Udine, tickets can be found at the bus station.
For more information on Trieste airport and connecting services check:

Treviso airport  (IATA code TSF) is about 30 km from Venice and 3 km from the CITY centre. public bus service (number 6) operates every 30 minutes from/to Treviso railway station. The journey takes about 15-20 minutes. From the railway station you may catch a train to Udine on the Venezia/Mestre – Udine line (no need to go to Venezia).
For more information on Venice airport and connecting services check:
For train connections:

By train
Udine is on the line Venezia-Vienna. Trains run almost every hour. The journey takes about 2 hours. Some trains require supplements or seat reservation. For train connections:

By car
Udine is on the A23 motorway Udine-Tarvisio. If you are approaching via the A4 Venezia-Trieste motorway, exit at “Udine Sud”. Detailed information is available at




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