PREFACE

A. Jakoviċs

Laboratory for Mathematical Modelling of Environmental and Technological Processes, University of Latvia, 8 Zeļļu str., LV-1002, Riga, Latvia

Abstract
The 6th International Scientific Colloquium "{ċ Modelling for Material Processing}" took place in Riga on 16--17 September, 2010. The first colloquium of this traditional series had taken place in 1999. All colloquia were organised by the Laboratory of Mathematical Modelling of Environmental and Technological Processes, University of Latvia, in cooperation with the Institute of Electrotechnology, Leibniz University of Hannover (Germany) what continues a long tradition (since 1988) of scientific cooperation in the field of electrothermal process modelling between researchers -- physicists and engineers of these two universities. During the latter colloquium, a wide range of mathematical modelling applications for industrial electromagnetic processing of materials was represented including -- heating of metallic materials; -- melting, alloying and crystallisation of melts; -- single crystal growth technologies; -- application of electromagnetic forces; -- multiphase mass and heat exchange. The total number of 45 attendants coming from 12 countries has met completely the expectations of the hosts. The 53 contributions were divided between 33 oral presentations and 20 posters. The most representative reports in the field of MHD have been selected to be published in the form of a special issue of the international journal Magnetohydrodynamics. The submitted reports demonstrate that the complexity of models for simulation of turbulent heat and mass exchange in liquid metal flows in different melting technologies for crystallization of alloys and single crystal growth under electromagnetic impact has significantly grown. An adequate description of occurring physical phenomena, their interaction and the use of high performance computer clusters allow to reduce essentially the number of experiments in industrial facilities needed for parameter studies. A new trend is the use of not only commercial modelling software like FLUENT, ANSYS, CFX, COMSOL or self-developed specific software for particular applications, but also the licence-free codes like OpenFoam with user specific implementations. This approach finds more and more success not only in researches performed at universities, but also in industrial companies. In all cases, the success in numerical modelling and in achieving industrially relevant results, in particular, in case of multiphysical models with a complex system geometry is determined by optimal solutions of "technical" problems, e.g., the creation of well-balanced meshes with high resolution in relevant sub-regions but with a moderate total number of nodes; optimal parallelization of the calculation scheme for a given number of processors and structure of the cluster; highly efficient coupling from different solvers and accelerating of data exchange between the system components, and, the last but not the least, the development of effective methods for post processing and visualization of transient 3D multi-field calculation results for their further physical interpretation and for application in engineer designs of equipment. The European Union co-financing projects (ERDF and ESF) in the field of numerical modelling realised since 2006 haves a very high positive effect involvement and motivation of PhD students and young scientists to make industrial-orientated MHD researches and on promotion of successful collaboration of Latvian scientists with universities and industrial companies in Germany, France, United Kingdom, Sweden and Switzerland. Currently, engineering physics, the core of which is the computer modelling of technological and environmental processes, is one of the largest and most successfully developing trends of research and study programs at the Department of Physics of the University of Latvia, with very good perspectives in the future aimed at the development of new technologies and sharing of knowledge.