2 nd sino-german workshop on epm (dresden)
DESCRIPTION
2 nd Sino-German Workshop on EPM (Dresden) Experimental studies of bubble-driven liquid metal flows in a static magnetic field C. Zhang, S. Eckert, G. Gerbeth Forschungszentrum Rossendorf, Dresden - Germany. Background & Motivation. - PowerPoint PPT PresentationTRANSCRIPT
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MHD DepartmentInstitute of Safety Research
2nd Sino-German Workshop on EPM (Dresden)
Experimental studies of bubble-driven liquid metal flows in a static magnetic field
C. Zhang, S. Eckert, G. Gerbeth
Forschungszentrum Rossendorf, Dresden - Germany
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MHD DepartmentInstitute of Safety Research
Background & Motivation
• Numerous applications of bubble-driven flows and magnetic fields in metallurgical engineering
• Combination of gas bubble injections and magnetic fields
• Comprehensive understandings of such MHD two-phase flows
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MHD DepartmentInstitute of Safety Research
Scalar quantity transportations in MHD flows
• A static magnetic field might both increase and decrease the heat transfer rate in enclosed thermal convections
– T. Tagawa & H.Ozoe, J. Heat Transfer 120, 1027-1032
– U. Burr & Mueller, 2002. J. Fluid Mech 453, 345-369
– G. Authie, et al., 2003, Eur. J. Mech. B/Fluids 22, 203-220
• Flow field information are highly desirable
• How about bubble-driven flow in a magnetic field?Single bubble motion; bubble plume flow
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MHD DepartmentInstitute of Safety Research
Bubble-driven flow: experimental setup
• Cylindrical container aspect ratio=2.5
• Liquid metal – GaInSn
• Single Ar bubble or bubble plume Qmax=8cm3/s
• A vertical longitudinal magnetic field or a horizontal transverse magnetic field, B=0 - 0.2T
• UDV measurements of the vertical and radial component velocity
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MHD DepartmentInstitute of Safety Research
Single bubble rising in a longitudinal magnetic field
Rising bubble
Bubble wake
US transducer
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MHD DepartmentInstitute of Safety Research
Bubble wake modified by the longitudinal magnetic field
B=0 B0
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MHD DepartmentInstitute of Safety Research
Bubble drag coefficient modified by the longitudinal magnetic field
0.01 0.1 1 100.7
0.8
0.9
1.0
1.1
1.2
CD /
CD(N
=0)
N
Eo=2.2 Eo=2.5 Eo=3.4 Eo=4.9 Eo=6.62
el TN B L /( u )
Magnetic interaction number:
ratio between electromagnetic and inertial force (N = 0 ... 1.3)
2egd
Eo
Bubble Eötvös number
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MHD DepartmentInstitute of Safety Research
Bubble velocity oscillation frequency and amplitude modified by the longitudinal magnetic field
0.02 0.1 1 30.7
0.8
0.9
1.0
1.1
St /
St(
N=
0)
N
Eo=2.2 Eo=2.5 Eo=3.4 Eo=4.9 Eo=6.6
0.02 0.1 1 3
0.6
0.7
0.8
0.9
1.0
1.1
A/A
(N=
0)
N
Eo=2.2 Eo=2.5 Eo=3.4 Eo=4.9 Eo=6.6
St = fde/uT
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MHD DepartmentInstitute of Safety Research
Bubble plume-driven flow in the transverse magnetic field- Spatial properties (Q=0.37cm3/s)
B=0 B=0.06T
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MHD DepartmentInstitute of Safety Research
Bubble plume-driven flow in the transverse magnetic field- Spatial properties (Q=0.37cm3/s)
B=0.11T B=0.17T
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MHD DepartmentInstitute of Safety Research
Bubble plume-driven flow in the transverse magnetic field- Spatial properties (Q=3.7cm3/s)
B=0 B=0.06T
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MHD DepartmentInstitute of Safety Research
Bubble plume-driven flow in the transverse magnetic field- Spatial properties (Q=3.7cm3/s)
B=0.11T B=0.17T
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MHD DepartmentInstitute of Safety Research
Bubble plume-driven flow in the transverse magnetic field-Radial component void fraction distribution measurements
B
Container cross-section view 0.0 0.2 0.4 0.6 0.8 1.0
0.00
0.01
0.02
0.03
0.04
0.05 B=0 radius perpendicular to B B=0 radius parallel to B B=0.13T radius perpendicular to B B=0.13T radius parallel to B
void
frac
tion
R
Q=7cm3/s
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MHD DepartmentInstitute of Safety Research
Bubble plume-driven flow in the transverse magnetic field- Temporal properties (Q=4.0cm3/s)
Q=5cm3/s R=0.87
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MHD DepartmentInstitute of Safety Research
Bubble plume-driven flow in the transverse magnetic field- Temporal properties (Q=4.0cm3/s)
Q=5cm3/s R=0.87
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MHD DepartmentInstitute of Safety Research
Summary
• The non-intrusive UDV measuring technique allows us to look into the opaque liquid metal flows
• A DC transverse magnetic field modifies both the spatial and temporal properties of the ordinary bubble-driven flow
• DC magnetic field may enforce flow instabilities!(Continuous casting + EMBR)
• Potential tools for controlling liquid metal flows in metallurgical engineering
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MHD DepartmentInstitute of Safety Research
Perspectives for future research projects
Potential topics of interest:– Liquid metal mixing enhancement
(control of heat and mass transfer in bubble plumes)– Gas phase distributions– Free surface stabilization– Continuous casting– …
FZR: Capacity of EPM model experiments in metallurgical engineering– Liquid metal model experiments– Magnetic fields (tailored fields MULTIMAG facility)– Measuring techniques
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MHD DepartmentInstitute of Safety Research
Acknowledgement
The research is supported by the Deutsche
Forschungsgemeinschaft (DFG) in the form of the SFB
609 “Electromagnetic Flow Control in Metallurgy,
Crystal Growth and Electrochemistry”.
This support is gratefully acknowledged by the authors.
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MHD DepartmentInstitute of Safety Research
Magnetic field influence on the liquid velocity distribution in the container meridional plane
-50 -25 0 25 500
50
100
150
200
Radius [mm]
He
igh
t [m
m]
-50 -25 0 25 500
50
100
150
200
-35.0-30.0
-25.0
-20.0
-15.0
-10.0
-5.00
0
5.00
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.055.0
60.0
65.0
Radius [mm]
Q=20sccm
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MHD DepartmentInstitute of Safety Research
Vortex structure evolution in a static magnetic field
P. Davidson. 1995, JFM, 299, 153-186
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MHD DepartmentInstitute of Safety Research
)( Buj el
BuuBBuuBBu
)()()()()(
uBj el
)( 0
j
0 j
02
0wallu
0/ wallwally yj
const
when the velocity is uniform in the direction of the magnetic field, then
current density is a potential, namely
so there is no Joule dissipation in such case. Accordingly, the Joule dissipation can be reduced by forming the two-dimensional vortical structures along the magnetic field line direction.
D. Lee & H. Choi, JFM, 2001, 439. 367-394
by taking the curl of both sides and using the equation
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MHD DepartmentInstitute of Safety Research
Bubble drag coefficient modified by the longitudinal magnetic field
lT
eD
u
gdC
23
4
0.1 0.2 0.4 0.6 0.8 1 20.7
0.8
0.9
1.0
1.1
1.2C
D(N
) / C
D(N
=0)
N
Eo=2.7 Eo=4.1 Eo=4.4 Eo=5.9 Eo=6.4 Eo=6.9
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MHD DepartmentInstitute of Safety Research
Bubble velocity oscillation frequency and amplitude modified by the longitudinal magnetic field
0.1 0.2 0.4 0.6 0.8 1 20.9
1.0
1.1
1.2
1.3
1.4
St(
N)
/ St(
N=
0)
N
Eo=2.7 Eo=4.1 Eo=4.4 Eo=5.9 Eo=6.4 Eo=6.9
0.1 0.2 0.4 0.6 0.8 1 20.0
0.2
0.4
0.6
0.8
1.0
1.2
A(n
) / A
(N=
0)
N
Eo=2.7 Eo=4.1 Eo=4.4 Eo=5.9 Eo=6.4 Eo=6.9