The Fifth International Conference 'Turbulent Mixing and Beyond'

The Fifth International Conference 'Turbulent Mixing and Beyond' (TMB-2014) has been held on 04–09 August 2014 at the Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy. It has been a part of the program 'Turbulent Mixing and Beyond' (TMB) and the regular ICTP activity 'Mixing in Rapidly Changing Environments—Probing Matter at the Extremes'. The TMB-2014 has been focused on hydrodynamic instabilities and on interfacial and turbulent mixing in fluids, plasmas and materials under extreme conditions of high energy density and sharply changing flow fields, and on their applications in nature and technology, from atomic to astrophysical scales.

The program 'Turbulent Mixing and Beyond' was developed in 2007 with the support of the international scientific community, and the international funding agencies and institutions, including the National Science Foundation, USA; European Office of Aerospace Research and Development (EOARD), UK, of the Air Force Office of Scientific Research (AFOSR), USA; Office of Naval Research Global (ONRG), UK; US Department of Energy, USA; US Department of Energy Los Alamos National Laboratory (LANL), USA; US Department of Energy Lawrence Livermore National Laboratory (LLNL), USA; US Department of Energy Argonne National Laboratory (ANL), USA; Commissariat à l'Energie Atomique et aux Energies alternatives (CEA), France; The Abdus Salam International Centre for Theoretical Physics, Italy; The University of Chicago, USA; The Carnegie Mellon University, USA; The New York University, USA; The Institute for Laser Engineering (ILE), Osaka University, Japan; The Joint Institute for High Temperatures of the Academy of Sciences, Russia; Photron (Europe) Ltd, UK; The Institute of Physics Publishing, UK. The program has been organized to bring together researchers from different areas of science, engineering and mathematics and to focus their attention on the fundamental problem of non-equilibrium dynamics and mixing.

The 'Turbulent Mixing and Beyond' is now the well-established scientific program. The goals of the program are to expose the generic problem of non-equilibrium and turbulent processes to a wide scientific community, to promote the development of new ideas in tackling the fundamental aspects of the problem, to assist in application of novel approaches in a broad range of phenomena, where these processes occur, and to have a potential impact on technology.

The TMB program was a major success on the sides of intellectual merit, broad impact, and community development. In 2007, 2009 and 2011, the TMB conferences have been hosted by the ICTP. In 2013 the TMB conference has been held as the invited mini-conference 'Mixing in fusion plasmas' at the 55 Annual Meeting of the Division of Plasmas Physics of the American Physical Society. The TMB-2014 has been held at the ICTP as the regular activity 'Mixing in Rapidly Changing Environments—Probing Matter at the Extremes'.

The TMB-2014 has been a highly informative and exciting meeting. The success of the TMB-2014 has consisted from the successful work of its participants, who work in the areas of fluid dynamics, plasmas, astrophysics, material science, nonlinear physics, and applied mathematics, and who are responsible professionals caring for the quality of their research and sharing their scientific vision.

The target problems of the TMB-2014 have included the Rayleigh–Taylor instabilities (RTI) and interfacial mixing, turbulent mixing, active and passive scalar mixing, and evolution of phase boundaries and convection in fluids, plasmas and materials, and their applications in fusion, astrophysics, reactive flows, material science, and aerodynamics. The special attention at the TMB-2014 has been paid to the mixing in fusion plasmas, including the inertial confinement fusion (ICF).

The RTI and interfacial mixing control a broad variety of processes in fluids, plasmas and materials. These processes can be natural or artificial, their characteristic scales can be astrophysical or atomistic, and energy densities can be low or high. In everyday life, we observe RTI and ensuing interfacial mixing while looking at how water flows from an overturned glass. Somewhat similar processes influence the formation of 'hot spot' in ICF, limit radial compression of imploding Z-pinches, drives penetration of stellar ejecta into pulsar wind nebula, determine momentum transfer in buoyancy-driven and magneto- convection, control material transformation under impact, and strongly affect dynamics of reactive and supersonic flows, either wall-bounded or free. A good grip on mixing processes is crucial for the cutting-edge technology in laser micromachining and for traditional industrial applications in the areas of aeronautics and aerodynamics. In some of these applications (e.g., combustion processes, supernova explosion), the mixing process should be enhanced, whereas in some others (ICF, light-material interaction, impact dynamics) it should be mitigated. In all circumstances, 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, thus addressing the goals of the 'Turbulent Mixing and Beyond' program.

The TMB community unites currently thousands of researchers. Google.com search returns for 'Turbulent Mixing and Beyond' over a million results. The TMB community is expected to grow, and its natural bounds are established by the requirements of academic credentials and quality of research. In 2014, the Fifths International TMB Conference has brought together nearly 120 international participants, from developed and from developing countries, ranging from graduate and undergraduate students to members of national academies of sciences and engineering, and including researchers at early and experienced stages of their carriers, from the leading scientific institutions in academia, national laboratories, corporations and industry.

The TMB-2014 has been structured to encourage the participants' communications with experts from various fields, to promote the exchange of ideas, 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 TMB-2014 has consisted of keynote and invited lectures by international experts, contributed talks and poster presentations by participants, and round tables discussions.

The focus topics of the TMB-2014 have included:

• Interfacial dynamics and hydrodynamic instabilities: instabilities of Rayleigh–Taylor, Kelvin–Helmholtz, Richtmyer–Meshkov, Landau–Darrieus, Saffman–Taylor; formation and evolution of phase boundaries, interfacial mixing.
• Turbulence and mixing: canonical and non-canonical turbulence, convection, rotating fluids, reactive and supersonic flows, active and passive scalar mixing.
• High energy density physics: inertial confinement, magnetic and heavy-ion fusion, Z-pinches, light-material and laser-plasma interaction, non-equilibrium heat transfer, material science, astrophysical applications.

At the same time, the TMB-2014 has covered 16 different topics, maintaining the scope and the interdisciplinary character of the Conference. These are: Canonical Turbulence and Turbulent Mixing; Wall-Bounded Flows; Non-Equilibrium Processes; Inter-facial Dynamics; High Energy Density Physics; Material Science; Astrophysics; Magneto-hydrodynamics; Canonical Plasmas; Physics of Atmosphere; Geophysics and Earth Science; Combustion; Mathematical Aspects of Non-Equilibrium Dynamics; Stochastic Processes and Probabilistic Description; Experimental Diagnostics. The focus of the TMB-2014 presentations has kept on the generic scientific problem of non-equilibrium dynamics and on achieving the Conference objectives.

The 121 contributions of 283 authors have been submitted to the TMB-2014 and have been considered by the 15 members of the Scientific Advisory Committee. The abstracts of the accepted presentations have been published in the TMB-2014 Proceedings, ISBN 978-9295003-55-2. Based on the scientific merit and quality of the results, several contributed talks have been selected as the invited lectures. Nearly 40 invited lectures, 60 regular talks and 20 poster presentations have been given.

The Round Tables have been held at the TMB-2014. The Round Table Discussions are a distinct feature and a tradition of the TMB Conferences. The objectives of the Round Tables are to encourage the information exchange among the members of the interdisciplinary and international TMB community, promote discussions of the state-of-the-art in the TMB-related scientific areas, identify directions for frontier research, and articulate recommendations for future developments.

The major scientific findings of the program 'Turbulent Mixing and Beyond' are: (i) The TMB-related problems (while spanning atomic to astrophysical scales, and low to high energy density conditions) have in common a set of outstanding research issues. (ii) Their solution has the potential to provide paradigm-shifting advances in a variety of disciplines in science, technology, and mathematics. (iii) The TMB community develops actively and yields a highly professional innovative research.

At the TMB-2014, we found that RTI and interfacial mixing control a broad variety of processes in fluids, plasmas and materials. They are crucial to study in order to understand and extend the range of applicability of traditional statistically steady approaches, and to capture the essentials of a wide range of phenomena in nature and technology. Their solution can significantly advance a range of disciplines in science, technology and mathematics.

The RTI and interfacial mixing are present everywhere, and are exceedingly difficult to study in their direct manifestation. 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 to exa-scale level and demands significant improvement 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) renders the unparalleled opportunities to explore the properties of mixing and to touch the matter at the extremes. This success, as well as the striking similarity in behavior of RT instabilities and mixing in the vastly different physical regimes, make this moment right for integrating our knowledge of the subject and for further enriching its development.

The TMB-2014 has exposed the generic problem of hydrodynamic instabilities and mixing to a wide scientific community, has promoted the development of new ideas in tackling the fundamental aspects of the problem, and has started to bridge the gap between the fundamental research and the state-of-the-art technology.

Further details on the TMB-2014 intellectual merit can be found in the TMB-2014 publications.

The aspects of development, training, and education are important for the success of the TMB program. With regard to development, the TMB-2014 has served to develop new ideas in tackling the fundamentals of the RTI and mixing, and to bridge the existing capability gap between the fundamental research and the state-of-the-art technology. With regard to the training and education, significant efforts have been undertaken at the TMB-2014 to attract young researchers and to provide them with advanced learning opportunities. These included the fundamental character of the problems considered, the emphasis on connections to technology, the scientific-merit-based evaluation criteria, the transparency of processes of selections and competitions, and the possibility to participate in the round tables. Many of the participants of the TMB-2014 were the researchers at earlier stages of their carriers, and some of them have been financially supported. These young researchers have been offered the opportunities to closely interact with experienced scientists from academia, national laboratories and corporations, and to discuss their results and ideas with scientists working at research frontiers and with cutting-edge technologies as well as with the founders of the scientific schools.

Over 40 young researchers participated in the competition for the award TMB4U 'Turbulent Mixing and Beyond for Youth'. Since 2009, this award is issued to a researcher at early stages of his/her carrier for recognition of his/her scientific contribution to the field of 'Turbulent Mixing and Beyond'. The selection has been made by the members of Scientific Advisory Committee on the basis of merit, novelty and quality of the results. At the TMB-2014 the award 'Turbulent Mixing and Beyond for Youth' (TMB4U) has been issued to Mr Nicolas Schneider from the Commissariat à l'Energie Atomique (France) and Mr Jason Olsthoorn from the University of Cambridge (UK). The Award for Best Poster has been issued to Mr Timothy Alexander de Haas from the University of California Los Angeles (USA).

The high quality publications are important for the success of 'Turbulent Mixing and Beyond' program. The TMB-2014 publications include this Focus Issue, the TMB-2014 Proceedings, the TMB-2014 Program, the TMB-2014 web-sites, and the video-recording of the TMB-2014 presentations.

The impact on the development of the principal discipline that has been provided by the program 'Turbulent Mixing and Beyond' and the TMB-2014 is in the discovery of fundamental properties of hydrodynamic instabilities and interfacial mixing, including their ordered character, in the development of new methods for tacking the fundamentals of hydrodynamic instabilities and mixing, and in the identification of a new class of scientific problems, whose solution can significantly advance a variety of disciplines in science, mathematics, and technology. The success in the solution of the highly fascinating problem of hydrodynamic instabilities and mixing requires collaborative efforts. The TMB program serves to organize this effort, to maintain the information flux in the TMB community, and to keep the focus on the quality of research.

The impact on other disciplines that has been provided by the program 'Turbulent Mixing and Beyond' and the TMB-2014 are due the essentially interdisciplinary character of the TMB program. Hydrodynamic instabilities and interfacial and turbulent mixing play a critical role in a broad variety of processes in fluids, plasmas and materials in nature and technology. Solution of this formidable problem can yield the advances in predictive modeling capabilities of the non-equilibrium dynamics, can further equip the scientific community with new methodologies for data assimilation and processing, and can help to elaborate the criteria of quality and information capacity of experimental and numerical data sets.

The impact on the community development that has been provided by the program 'Turbulent Mixing and Beyond' and the TMB-2014 are due to the following unique features of the TMB program: this program is essentially interdisciplinary and international, is focused on challenging and fundamental problems, and pays particular attention to quality of research. These features make the program attractive to both first-rate experienced researchers and for researchers at early stages of their carriers. They also enable a positive and creative environment that helps the community members to maintain professional attitude, expand their creativity, develop productive interactions and collaborations, and approach research objectives.

The development of institutional, educational and information resources that form infrastructure is an important part of the 'Turbulent Mixing and Beyond' program. In order to provide impact on the development of these resources, at the TMB conferences, the lectures and presentations are digitally recorded, and the Proceedings, the Program and the presentations are placed at the web-site. This serves to turn the frontier research and state-of-the-art technology into a great institutional, educational and information resource that is freely available to the public.

Regarding the impact on society beyond science and discipline, the 'Turbulent Mixing and Beyond', as the program developed for scientists by scientists, is grounded on the criteria of scientific merit. It brings together individuals from developed and developing countries, women, minorities and under-represented groups. It unites leading experts and researchers at experienced and early stages of their carriers from academia, national laboratories, corporations and industry, as well as undergraduate and graduate students. For their inquisitive minds, the program suggests the fundamental scientific problem, that, on the one hand, occurs in numerous and diverse circumstances, and, on the other hand, play important role in technological applications.

To conclude, the TMB program is organized to advance the state-of-the-art in understanding of fundamental physical properties of non-equilibrium and turbulent processes, and to have an impact on predictive modeling capabilities, physical description and, ultimately, control of these complex processes. The readers are cordially invited to take a look at this Focus Issue for information on the frontiers of theoretical, numerical and experimental research, and state-of-the-art technology.

Welcome to 'Turbulent Mixing and Beyond'.

The Fifth International Conference TMB-2014 has been organized by the following members of the Organizing Committee:

• Snezhana I Abarzhi (University of Western Australia, AU; Carnegie Mellon University, USA)
• Sergei I Anisimov (Landau Institute for Theoretical Physics, Russia)
• Hiroshi Azechi (Institute for Laser Engineering, Japan)
• Serge Gauthier (Commissariat à l'Energie Atomique, France)
• Joseph J Niemela (International Centre for Theoretical Physics, Italy)
• Evgeny E Meshkov (National Nuclear Research University, Russia)
• Bruce R Remington (Lawrence Livermore National Laboratory, USA)
• Katepalli R Sreenivasan (New York University, USA)

The Conference has been supported by several international institution and funding agencies. The Organizing Committee of the TMB-2014 gratefully acknowledges the financial support of:

• The Abdus Salam International Centre for Theoretical Physics (ICTP), Italy
• The National Science Foundation (NSF), USA
• The European Office of Aerospace Research and Development (EOARD), UK, of the Air Force Office of Scientific Research (AFOSR), USA
• The Office of Naval Research Global, UK
• The Department of Energy, Office of Science, USA
• The US Department of Energy Lawrence Livermore Natl. Laboratory (LLNL), USA
• The Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), France
• The Carnegie Mellon University, USA
• The Institute for Laser Engineering (ILE), Japan
• The Institute of Physics Publishing (IOP), UK

We thank the ICTP Activity Secretariat for making this event possible:

• Ms Ave Lusenti (activity secretary, ICTP, Trieste, Italy)
• Ms Patricia Wardell (activity secretary, ICTP, Trieste, Italy)

We express our gratitude to the members of the Scientific Advisory Committee:

• S I Abarzhi (University of Western Australia, AU; Carnegie Mellon University, USA)
• Y Aglitskiy (Science Applications International Corporation, USA)
• H Azechi (Institute for Laser Engineering, Osaka, Japan)
• M J Andrews (Los Alamos National Laboratory, USA)
• S I Anisimov (Landau Institute for Theoretical Physics, Russia)
• E Bodenschatz (Max Plank Institute for Dynamics and Self-Organization, Germany)
• A Casner (Commissariat à l'Energie Atomique, France)
• S Cowley (Imperial College, UK)
• S Dalziel (DAMTP, Cambridge University, UK)
• R Ecke (Los Alamos National Laboratory, USA)
• Y Fukumoto (Kyushu University, Japan)
• S Gauthier (Commissariat à l'Energie Atomique, France)
• W Gekelman (University of Calfornia Los Angeles, USA)
• J J Glimm (SUNY Stony Brook, USA)
• W A Goddard III (California Institute of Technology, USA)
• L P Kadanoff (The University of Chicago, USA)
• D I Meiron (California Institute of Technology, USA)
• E E Meshkov (VNIIEF, Russia)
• P Moin (Stanford University, USA)
• A Nepomnyashchy (Technion, Israel)
• J Niemela (International Center for Theoretical Physics, Italy)
• K Nishihara (Institute for Laser Engineering, Osaka, Japan)
• N Peters (RWTS, Aachen, Germany)
• A Pouquet (National Center for Atmospheric Research, USA)
• B A Remington (Lawrence Livermore National Laboratory, USA)
• A J Schmitt (Naval Research Laboratory, USA)
• V Smalyuk (Lawrence Livermore National Laboratory, USA)
• K R Sreenivasan (New York University, USA)
• A L Velikovich (Naval Research Laboratory, USA)
• V Yakhot (Boston University, USA)
• F A Williams (University of California at San Diego, USA)

We deeply appreciate the work of the members of Steering Committee for Financial Support:

• Snezhana I Abarzhi (Carnegie Mellon University, USA)
• Serge Gauthier (Commissariat à l'Energie Atomique, France)
• Joseph J Niemela (International Centre for Theoretical Physics, Italy)
• Katepalli R Sreenivasan (New York University, USA)

We thank the members of the Committee for Young Scientist Award:

• Hiroshi Azechi (Institute for Laser Engineering, Japan)
• Boris Galperin (University of South Florida, USA)
• Serge Gauthier (Commissariat à l'Energie Atomique, France)
• Walter Gekelman (University of California at Los Angeles, USA)
• Joseph J Niemela (International Centre for Theoretical Physics, Italy)
• Bruce R Remington (Lawrence Livermore National Laboratory, USA)
• Katepalli R Sreenivasan (New York University, USA)

We gratefully acknowledge the effort of the member of the Committee for Best Poster Award:

• Serge Gauthier (Commissariat à l'Energie Atomique, France)
• Walter Gekelman (University of California at Los Angeles, USA)
• Joseph J Niemela (International Centre for Theoretical Physics, Italy)
• Katsunobu Nishihara (Institute for Laser Engineering, Osaka, Japan)
• Bruce R Remington (Lawrence Livermore National Laboratory, USA)

We gratefully appreciate the work of the TMB program web-master:

• Dan Ilyin (California Institute of Technology, USA)

We thank for the technical support:

• Daniil V Ilyin (California Institute of Technology, USA)
• Zachary Dell (Carnegie Mellon University, USA)
• Maher H Khan (Carnegie Mellon University, USA)
• Syed H Mehdi (Carnegie Mellon University, USA)
• Nora Swisher (Carnegie Mellon University, USA)

We gratefully appreciate the publishing support of:

• Brian Andrew Chavez (Lawrence Livermore National Laboratory, USA)
• Raffaele Corona (International Centre for Theoretical Physics, Italy)
• Fabrizio Coana (International Center for Theoretical Physics
• Arun Pandian (Carnegie Mellon University, USA)
• Ulrich Singe (International Centre for Theoretical Physics, Italy)

We warmly acknowledge the logistics assistance of the ICTP offices and officers:

• Conference Support Office, and Ms Ave Lusenti and Ms Patricia Wardell
• Financial Office, and Mr Andrej Michelcich, Mr Ulrich Singe and Ms Alessandra Ricci
• Visa Office, and Mr Erich Jost and Mr Adriano Maggio
• Housing Office, and Ms Tiziana Bottazzi and Ms Dora Photiou
• Publications Office, and Mr Guido Comar and Mr Raffaele Corona
• Computer Office, and Dr Johannes Grassberger
• Science Dissemination Unit, and Dr Enrique Canessa, Dr Carlo Fonda and Dr Marco Zennaro

We gratefully appreciate the support of the members of the Program Coordination Board:

• Snezhana I Abarzhi (University of Western Australia, AU; Carnegie Mellon University, USA)
• Malcolm J Andrews (Los Alamos National Laboratory, USA)
• Sergei I Anisimov (Landau Institute for Theoretical Physics, Russia)
• Hiroshi Azechi (Institute for Laser Engineering, Osaka, Japan)
• Vladimir E Fortov (Institute for High Energy Density, Russia)
• Serge Gauthier (Commissariat à l'Energie Atomique, France)
• Christopher J Keane (Lawrence Livermore National Laboratory, USA)
• Joseph J Niemela (International Centre for Theoretical Physics, Italy)
• Katsunobu Nishihara (Institute for Laser Engineering, Osaka, Japan)
• Sergei S Orlov (Physical Optics Corporation, USA)
• Bruce A Remington (Lawrence Livermore National Laboratory, USA)
• Robert Rosner (University of Chicago, USA)
• Katepalli R Sreenivasan (New York University, USA)
• Alexander L Velikovich (Naval Research Laboratory, USA)