Modeling of Induced Surface Oscillation Damping Behavior in Levitated Molten Metal Droplets
Xiao, Xiao.
2017
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Abstract: Measurement
of thermophysical properties including the temperature-dependent viscosity of molten
metals is important in material research. Microgravity Electromagnetically levitation
(EML) experiments on board the International Space Station (ISS) were launched to
measure the viscosity of levitated molten metal droplets through the analysis of the
damping behavior of oscillations ... read moreinduced by pulse excitations. The work presented here
contributes in the following areas. Firstly, the damping behavior of the oscillating
droplet could be evaluated from the two-dimensional projected image signals of the
sample droplet using an elliptical fit, and the time-temperature-dependent damping rate
of the oscillating droplet could be derived through appropriate segmentations of the
oscillating signals. Secondly, possible factors that would influence the damping rate
analysis and viscosity measurement are evaluated, including the power settings of EML
coil, test temperature of the molten metal liquid, and the magnitude and distribution of
oscillation modes for droplet deformation. Thirdly, the oscillation transition behavior
of the damped signal is presented which reflects in an overestimated damping rate and an
increased apparent viscosity of the droplet primarily due to the turbulent convection
inside the droplet induced from the heater pulse. An empirical estimation of the time
scale for turbulence decay is established based on the experimental data and
Magnetohydrodynamic(MHD) simulation results. Finally, a guideline is provided for
parameter design for viscosity measurement experiments using the ISS EML facility. Based
on these analyses, space results are compared to previous containerless results and
although each data set shows similar accuracy, the precision of the measurements is
shown to vary by 10.7% for ground-based electrostatic levitation, and 13.8% for
parabolic flight EML as compared to 7.4% for the new space EML results presented in this
work.
Thesis (Ph.D.)--Tufts University, 2017.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Douglas Matson.
Committee: Anil Saigal, Xiaozhe Hu, and Jonghyun Lee.
Keywords: Mechanical engineering, and Materials Science.read less - ID:
- v692tj52p
- Component ID:
- tufts:23112
- To Cite:
- TARC Citation Guide EndNote
