Flow Control by Tailored Magnetic Fields (FLOWCOMAG)

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Flow Control by Tailored Magnetic Fields
(FLOWCOMAG)

• April 1-2, 2004
• Jointly organized by Forschungszentrum
  Rossendorf (FZR)
• TU Dresden
• In frame of Collaborative Research Centre SFB
  609 (supported by DFG)
• Some introductory remarks
• G. Gerbeth
• Context, Basic Ideas, Some Examples

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Context

• Basic and applied studies on Magnetohydrodynamics
  (MHD)
• 20 years tradition at FZR
• 10 years tradition at TU Dresden (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
• supported by DFG
• supposed to last 11 years with 1.3 Mio /a

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Electrically conducting fluids liquid metals,
semiconductor melts, electrolytes
Context

• MHD NSE Lorentz Force
•   where

Volume force - nice tool to play with
the flow - can be arranged as needed -
contactless action, perfectly controllable -
several applications, industrial requests
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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
Basic Idea Tailored magnetic field systems

• 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

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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 strategies3) new
computer capabilities 4) MHD catalogue is well
filled
Basic Idea Tailored magnetic field systems

• 5) new level of velocity measuring techniques for
  liquid metal MHD flows (liquid metal model
  experiments up to T ? 400C)
• 6) new level of experimental tools for
  superposition of AC and DC magnetic fields

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PbBi bubbly flow at T ? 270C
Velocity measuring technique (example)
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Experimental platform for combined AC and DC
magnetic fields
MULTIMAG
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Examples for partly going the inverse way

• Industrial Cz-growth of single Si crystals
• Float-zone crystal growth
• Industrial Al investment casting
• Melt extraction of metallic fibers
• Seawater flows
• Electromagnetic levitation

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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
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Float-zone crystal growth

Solution secondary coil with phase shift acting
as a pump
Usual HF heater gives double-vortex in molten
zone Concave phase boundary is bad Goal
modified flow field in order to change the
solid-liquid phase boundary
Realization at IFW Dresden
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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
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Industrial Al investment casting

Magnetic control of the filling
process Material Al-Si-alloys
Problem high velocities lead to entrapment
of oxides and gas bubbles Solution Magnetic
brake by a) DC field ? done b) AC pump ? in
progress
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Melt extraction of metallic fibers

Magnetic stabilization of the free surface
(global DC field) the meniscus
oscillations (ferromagnetic edge)
Real process Model experiment
Results red no magnet steel fibers
with SnPb green with magnetic
control
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Electromagnetic levitation
Principle
Pronounced rotations and oscillations

Goal Stabilization of the probe Solution
Superimposed DC field no strong field needed,
but careful spatial design
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Electromagnetic levitation

DC-current added to the levitating coil
DC-field provided by permanent magnets
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Summary

• ? Flow control by magnetic fields nice tool to
  modify velocity fields
• inverse approach challenging task
• Several industrial requests, short bridge to
  applications
• Closer relation between communities of
  optimization/control and MHD very attractive
• Right time for FLOWCOMAG