Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Flow Control by Tailored Magnetic Fields Context, Basic Ideas, Some Examples Sino-German Workshop on Electromagnetic Processing of Materials (EPM) Shanghai University, Oct , 2004 G. Gerbeth Forschungszentrum Rossendorf (FZR), Dresden, Germany

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Magnetic Fields: Contactless influence on Processes and Materials Attractive R&D topic for the future Powerful research programs in China and Germany: Cooperation between Chinese and German teams (serious basis exists already) Exchange of students, Ph.D.’s, postdoc’s Joint R&D projects, joint industrial projects (?) Support by Sino-German Center for Research Promotion (founded by NSFC and DFG) is gratefully acknowledged Introduction: Sino-German Workshop on EPM

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Basic and applied studies on Magnetohydrodynamics (MHD): -20 years tradition at FZR -10 years tradition at Dresden University (TUD) -Local network in Dresden (IFW, Uni Freiberg, FhG, MPI) -Traditional cooperation and Twinning Agreement with Institute of Physics Riga (Latvia) Since 2002: Collaborative Research Centre SFB 609 at TUD “Electromagnetic flow control in metallurgy, crystal growth and electrochemistry” supported by DFG supposed to last 11 years with ~ 1.7 Mio €/a Introduction: MHD in Dresden (Germany)

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Electrically conducting fluids:liquid metals, semiconductor melts, electrolytes MHD = NSE + Lorentz Force where Context Volume force : - nice tool to play with the flow - can be arranged as needed - contactless action, perfectly controllable - several applications, industrial requests

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Up to now: Forward Strategy –What are the changes if some magnetic field is applied? Known magnetic field actions: DC fields:Flow damping AC-fields, low frequency: stirring and pumping AC-fields, high frequency: Heating and melting, levitation  MHD Catalogue Necessary: Transition to inverse approach 1) Which flow is desirable? 2) Which Lorentz force can provide this? 3) How to make this Lorentz force? Note: flow field often not the goal, just some intermediate agent Basic Idea: Tailored magnetic field systems

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Why now? 1) Strong request from applied side for smart solutions with low effort (Tesla cost money!) 2) powerful community for optimization, control theory, inverse strategies 3) new computer capabilities 4) MHD catalogue is well filled 5) new level of velocity measuring techniques for liquid metal MHD flows (liquid metal model experiments up to T  400°C) 6) new level of experimental tools for superposition of AC and DC magnetic fields Basic Idea: Tailored magnetic field systems

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 PbBi bubbly flow at T  270°C Velocity measuring technique (example)

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Experimental platform for combined AC and DC magnetic fields MULTIMAG

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Examples for partly going the inverse way 1)Industrial Cz-growth of single Si crystals 2)Float-zone crystal growth 3)Industrial Al investment casting Dr. Eckert 4)Melt extraction of metallic fibers 5)Seawater flows 6)Electromagnetic levitation Dr. Priede

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Industrial Cz-growth of single Si crystals Goals: - larger diameters (200  300) - stable growth process - homogeneous oxygen distribution Solution:AC fields for flow driving, DC fields for reduction of fluctuations Combined fields installed at Wacker Siltronic

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Float-zone crystal growth Usual HF heater gives double- vortex in molten zone Concave phase boundary is bad for the growth of single crystals of intermetallic compounds Goal: modified flow field in order to change the solid-liquid phase boundary

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Float-zone crystal growth Solution: secondary coil with phase shift acting as a pump Realization at IFW Dresden Parameters to adjust: Current amplitude and frequency, vertical distance between coils, C 1, R 1

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Float-zone crystal growth The principle action of such a two-phase stirrer Model experiments demonstration Single coil double coil double coil upwards pumping downwards pumping

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Optimum: distance  crystal radius Float-zone crystal growth Numerical simulations: electromagnetic fields, flow, temperature field Example: Variation of the vertical distance of the coils h = 1 mm h = 3 mmh = 5 mm

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Float-zone crystal growth Growth of NiSi5 Pumping action of the double inductor: downwards upwards

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Float-zone crystal growth Standard float-zone with double inductor 2 HoNi2B2C Fe87.5Si12.5 YNi2B2C Ni95Si5

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Extraction of steel fibers in an open industrial facility Melt extraction of metallic fibres

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Principle of the process Melt extraction of metallic fibres rapid quenching almost all materials (intermetallics, too) Diameter > 100 mikron Too broad distribution of fibre diameters

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Melt extraction of metallic fibers Magnetic stabilization of:the free surface (global DC field) +the meniscus oscillations (ferromagnetic edge) Model experiment Results: red – no magnet with SnPb green – with magnetic control

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Summary  Flow control by magnetic fields: nice tool to modify velocity fields inverse approach: challenging task Several industrial requests, short bridge to applications Essential tools: numerical simulations new class of velocity measuring techniques for liquid metals „cold“ model experiments Attractive basis in China and Germany Right time for a Sino-German Workshop

Forschungszentrum Rossendorf Sino-German Workshop on EPM Shanghai, Oct , 2004 Outlook for 2005 Joint 15th Riga and 6th PAMIR International Conference on Fundamental and Applied MHD Riga (Latvia), June 27 – July 1,  German-Chinese Workshop in Dresden: to be discussed