Turbulent Mixing and Beyond Workshop

Mixing in Rapidly Changing Environments

04-09 August 2014
The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy

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Outline of Themes


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Young Scientist Award

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Outline of Themes

Rayleigh-Taylor (RT) instabilities and interfacial mixing control a broad variety of processes in fluids, plasmas and materials. These processes can be natural or artificial, their characterstic scales can be astrophysical or atomistic, and every densities can be low or high. In everyday life we observe Rayleigh-Taylor instability (RTI) and ensuring turbulent mixing while looking at how water flows out from an overturned glass. Somewhat similar processes influence the formation of 'hot spot' in inertial confinement fusion (ICF), limit radial compression of imploding Z-pinches, drive penetration of stellar ejecta into pulsar win nebula, determine momentum transfer in buoyancy-driven and magneto- convection, control material transformation under impact, and strongly affect the dynamics of reactive and supersonic flows, either wall-bounded or free. A good grip on mixing process is crucial for the cutting-0edge technology in laser micro-machining and for traditional industrial applications in the areas of aeronautics and aerodynamics. In some of these applications (e.g. combustion processes, supernova explosion, turbulent mixing should be enhanced., whereas in some others (inertial confinement fusion, light-material interaction, impact dynamics) it should be mitigated. However, in all circumstanced, we have to understand the fundamentals of the mixing process, be able to gather high quality data and derive knowledge from these data, and, ultimately, achieve better control of these complex processes.

RT instabilities and interfacial mixing are present everywhere, and are exceedingly difficult to study in their direct manifestations. At macroscopic scales, their properties depart substantially from those of canonical Kolmogorov turbulence. At atomistic and meso-scales, their non-equilibrium dynamics differ from a standard scenario given by the Gibbs ensemble. Their theoretical description is intellectually challenging, as it has to account for the multi-scale, nonlinear, non-local and statistically unsteady character of the dynamics. Their numerical modeling effectively pushes the boundaries of computations and demands significant improvements of numerical methods in order to capture shocks, track interfaces, and accurately account for the dissipation processes, non-equilibrium and singularities. On the experimental front, these processes are a challenge to implement and systematically study in a well-controlled laboratory environment. they are sensitive to details and are transient, and their dynamics impose unusually tight requirements on the accuracy and resolution of flow measurements, as well as on data acquisition rates. Furthermore, because of their statistical unsteadiness, systematic interpretation of these processes from experimental data alone is neither easy nor straightforward. Despite these challenges, the tremendous success that has been recently achieved in large-scale numerical simulations, in laboratory experiments (especially those in high power laser systems), in technology development (including possibilities for improvements in precision, dynamic range, reproducibility, motion-control accuracy, and data acquisition rate), and in theoretical analysis (in particular, new approaches for handling complex multi-scale non-local and statistically unsteady transport) render unparallel opportunities to explore the properties of mixing and to touch the nature at the extremes. This success, as well as the striking similarity in behavior of RT instabilities and mixing in the vastly different regimes, make this moment right for integrating our knowledge of the subject and for further enriching its development.

The TMB Workshop "Mixing in Rapidly Changing Environments - Probing Nature at the Extremes" is structured to encourage the participants’ communications with experts from different fields, to promote the exchange of ideas and suggestion of open problems, and to motivate the discussions of rigorous mathematical issues, theoretical approaches and state-of-the-art numerical simulations along with advanced experimental techniques and technological applications. The sessions are intended to run sequentially.