1. Institute of Safety Research MHD department Experiments on the magnetic field influence on gas-liquid metal two-phase flows Chaojie Zhang, Sven Eckert, Gunter Gerbeth Forschungszentrum Rossendorf D-01314 Dresden, Germany Sino-German Workshop on Electromagnetic Processing of Materials Shanghai, China, 11 th -12 th, October, 2004

2. Institute of Safety Research MHD department Motivation Background numerous applications of magnetic fields and bubble- driven flows in metallurgy Our interest influence of external magnetic fields on the flow fields: gas bubbles and the induced liquid motions

3. Institute of Safety Research MHD department Measurements of local flow properties Difficulties opaqueness, high temperature, poor wettability, chemically aggressiveness Our approach application of the ultrasound Doppler velocimetry (UDV) DOP2000 (model 2125, Signal Processing SA )

4. Institute of Safety Research MHD department Ultrasound Doppler Velocimetry (UDV) Pulse-echo method information about the position  time of flight measurement information about velocity  Doppler relation (c - sound velocity, f D - Doppler frequency, f 0 - ultrasound frequency)

5. Institute of Safety Research MHD department Ultrasound Doppler Velocimetry (UDV) Advantages spatial-temporal velocity information non-intrusive method Prerequisites ultrasound transmission acoustic coupling reflecting particles Liquid metal applications Mercury( Takeda, 1991. Nucl. Eng. Design. Vol. 126) Gallium (Brito et al, 2001. Exp. Fluids. Vol. 31) Sodium (Eckert & Gerbeth, 2002. Exp. Fluids. Vol. 32) GaInSn (Cramer & Eckert, 2004. Flow Meas. Instrum. Vol. 15) PbBi, CuSn, Al (Eckert & Gerbeth et al, 2003 Exp. Fluids. Vol. 35)

6. Institute of Safety Research MHD department Test problem: bubble-driven flow LDA US Transducer Present experiments: bubble driven flow in water and glycerin UDV & LDA measurement Q=178mm 3 /s, 85% glycerin UDV: (channel bubbly flow) T.Wang: Chem. Eng. J., Vol. 92 Y.Suzuki: Exp. Therm Fluid Sci., Vol. 26

7. Institute of Safety Research MHD department Test problem: UDV results validation single bubble rising velocity in stagnant liquids LDA and UDV measured liquid velocity distributions along bubble chain centerline

8. Institute of Safety Research MHD department Bubble motion in a liquid metal column in a longitudinal D.C. magnetic field coil 1 coil 2 US transducer GaInSn GaInSn (melting point 10°C) singular Ar bubbles (d e = 4...8 mm) longitudinal D.C. magnetic field (B max = 0.3 T) magnetic interaction parameter N ratio between electromagnetic and inertial force (N = 0... 1.3)

9. Institute of Safety Research MHD department Bubble terminal velocity in GaInSn (B=0) waterGaInSnmercury Density 998636113610 Surface tension 0.0730.5330.482 Dynamic Viscosity 9.8e-42.2e-31.55e-3 Mendelson equation: Y.Mori: J. Heat. Transfer. Vol. 99 K. Schwerdtfeger: Chem. Eng. Sci., Vol. 23

10. Institute of Safety Research MHD department Bubble rising velocity evolutions in GaInSn

11. Institute of Safety Research MHD department The magnetic field influence on the ensemble- averaged bubble velocity evolutions

12. Institute of Safety Research MHD department Bubble drag coefficient modifications by the magnetic field

13. Institute of Safety Research MHD department Bubble velocity oscillation frequency and amplitude modification by magnetic field St = f  d e /u T.

14. Institute of Safety Research MHD department The magnetic field influence on the bubble wake B=0 B0B0 A rising gas bubble Wake region US transducer Bubble Eo=5.7

15. Institute of Safety Research MHD department Magnetic field influence on the liquid velocity distribution in the container meridional plane Q=20sccm

16. Institute of Safety Research MHD department Summary UDV was validated for the capacity in the relatively low gas flow rate gas-liquid metal two-phase flow measurements. The static longitudinal magnetic field was found to have a damping influence on the single bubble non-steady motion by modifying the bubble wake structure trailing behind. Liquid metal flow driven by the bubble swarm in the meridional plane showed that the static longitudinal magnetic field elongated the flow structures along the field line direction and damped the re-circulating flow region near the free surface.

17. Institute of Safety Research MHD department Acknowledgement The research is supported by the Deutsche Forschungsgemeinschaft (DFG) in form of the SFB 609 “Electromagnetic Flow Control in Metallurgy, Crystal Growth and Electrochemistry”. This support is gratefully acknowledged by the authors.

18. Institute of Safety Research MHD department

19. Institute of Safety Research MHD department A zigzag bubble structure in water at Re=1500 Left: visualization from Lunde & Perkins; right: interpretation by Brücker

20. Institute of Safety Research MHD department Vortex structure evolution in a static magnetic field