Fundamentals of technical applications of MHD

A summary of MHD effects and technical applications will be given based on a classification of the different actions of external magnetic fields and/or external electrical currents. An overview of the different alternating fields (rotating, pulsating, travelling) and static magnetic fields, and their interaction with liquid metal melts will be given. Special emphasis will be put on applications in crystal growth where a contactless melt flow control is important for the convective motions in many growth technologies. Typically steady magnetic fields are used to damp such flows. Surprisingly, active flow driving forces due to alternating magnetic fields can be of stabilizing character, too. Numerical results for the combined action of DC and AC magnetic fields will be presented for two problems: vertical Bridgeman and silicon Czochralski crystal growth. Recent results on MHD turbulence and some destabilizing actions of steady magnetic fields will shortly be mentioned. Special attention will be given to the problem of measuring techniques in liquid metal melts since this is a crucial question for any experimental activities in the field. For instance, any activity for code validation will require model experiments which, in turn, quickly lead to serious measuring problems. Some new results and ideas will be discussed.