Liu, Shuchen

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59th Annual Meeting of the APS Division of Fluid
Dynamics, Tampa Bat, Florida
Towed-Grid Studies of Quantum Turbulence

• Liu, Shu-chen
• Department of Physics
• University of Florida
• November 19th, 2006

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Outline

• Grid Turbulence in Liquid 4Helium
• Shielded Superconducting Linear Motor for
• Towed- Grid Turbulence Experiments
• Model Design
• Simulation Programs
• Experimental Cell Construction
• Superconductor Shield Construction
• Test Results
• Future Work

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Quantization of Vortices Lines
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Classical Grid Turbulence
Classical Homogeneous Isotropic Turbulence
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Differentiating between the Kolmogorov and
Kelvin-Wave Energy Spectra
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Kelvin Waves rotating helical wave
Quantized vortices can support a transverse and
circularly polarized wave motion (a Kelvin wave)
produced by vortex reconnections
or due to Donnelly-Glaberson instability.
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The Decay of Turbulence in Superfluid Helium 4
at Very Low Temperatures
Kelvin waves damp only by phonon radiation at a
high frequency Energy is injected at a low
frequency and dissipates by phonon emission at a
high frequency
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Shielded Superconducting Linear Motor for
Towed-Grid Turbulence Experiments

• -- Model Design

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Schematic Model
? Producing homogeneous isotropic turbulence
(HIT) within 20 ms
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Working Principles
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Magnetic force distribution along the z- axis of
the solenoid
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Grid Reynolds Number Re at Motor Testing
Temperature
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Current v.s. Time Curves for Superconducting
Shielded Motor System
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Velocity v.s. Position of Niobium Can 1 Curves
for Superconducting Shielded Motor System
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Experimental Cell
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Superconductor Shield Construction
Lead Electroplating
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Masterpieces with Lead Superconductor Shield
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Circuitry of the Motor Experiments
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Velocity v.s. Position of Armature Curves for
Unshielded Test Motor System
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Future Work

• Run the superconducting shielded
• linear motor system at 20mK in the
• dilution refrigerator.
• Explore the energy spectra and the
• decay mechanism in HIQT at 20mK.

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The End
Acknowledgement Professor Ihas
Greg Labbe Physics Cryogenic
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