Flowing matter lies at the crossroads between industrial processes, fundamental physics, engineering and Earth Sciences. Depending on the microscopic interactions, an assembly of molecules or of mesoscopic particles can flow like a simple Newtonian fluid, deform elastically like a solid or behave in a complex manner. When the internal constituents are active, as for biological entities, one generally observes complex large-scale collective motions. The phenomenology is further complicated by the invariable tendency of fluids to display chaos at the large scales or when stirred strong enough. A fundamental understanding of flowing matter is still missing impeding scientific progress, effective control on industrial processes, as well as accurate predictions of natural phenomena. Flowing matter frequently presents a tight coupling between small-scale structures and large-scale flow urging for a unifying approach. The Action will coordinate existing research efforts into a synergetic plan of collaborations and exchanges to develop an innovative multi-scale approach able to encompass the traditional micro-, meso-, and macro-scales descriptions. Breakthroughs in the understanding of flowing matter will impact on fundamental key scientific issues, such as the glass, the elasto-plastic and the jamming transitions, as well as industrial applications including health, energy, cosmetics, detergents, food, paints, inks, oil and gas.
Fluid turbulence is ubiquitous and so is its ability to transport particulate matter such as dust, soot or droplets. The dynamics of particles in a turbulent flow is fundamental to everyday life - examples of open scientific and technological issues include rain formation in clouds, pollution dispersion in the atmosphere, optimization and emission reduction in combustion, plankton population dynamics - and constitute a major scientific challenge with immediate practical implications and applications. Open scientific issues such as inertia, finite particles sizes, collisions, advection in complex flow geometries are examples of fundamental key ingredients which pose challenging theoretical problems and need to be understood in order to have an impact on applications. By joining forces within the experimental and numerical community of turbulence major breakthroughs can be achieved. The present COST action will create the needed platform for direct communication and interaction between participating laboratories and towards the wider scientific community alike.
Various recent studies have revealed amazing phenomena in the dynamics of bacterial colonies where biology meets physics, in particular statistical physics, fluid dynamics, and (soft) con- densed matter. These biological systems reveal analogies with complex fluids (isotropic- nematic phase transitions), spinodal decomposition phenomena in physics and materials sci- ence, and diffusion-limited reaction kinetics in chemistry. Moreover, gene segregation phe- nomena can be studied with tools from statistical physics (e.g., Potts-like models).
Life on Earth is invariably associated with (flowing) water. Fluid flows determine the fate of bacterial colonies and supply nutrients. Many studies focused on population dynamics in absence of fluid motion, e.g. bacteria living on a Petri dish or in a well-mixed medium. The life of plankton and cyanobacteria in oceans and lakes, however, is ruled by fluid transport, compressibility effects and particle-number fluctuations. Thus we face fundamental questions of how fluid mechanics and turbulence will affect the dynamics of bacterial colonies and their genetic evolution.