Type of Document Dissertation Author Hilton, David K URN etd-09012003-002313 Title Growth and Decay of Quantum Turbulence Induced by Second Sound Shock Pulses in Helium II Degree Doctor of Philosophy Department Physics, Department of Advisory Committee
Advisor Name Title James S. Brooks Committee Chair David M. Lind Committee Member Howard A. Baer Committee Member Lev P. Gorkov Committee Member Steven L. Blumsack Committee Member Steven W. Van Sciver Committee Member Keywords
- Transient Heat Transfer
- Quantum Turbulence
- Second Sound
Date of Defense 2003-06-01 Availability restricted AbstractNew to physics, the experiments of this dissertation successfully acquired clear and
extensive direct measurements in He II at 1.7 K of quantum turbulence induced by second sound shock pulses in a wide channel. Such pulses are moving volume sources of power flux density. The Vinen and Hall equation cannot be directly pplied to describe the induced quantum turbulence dynamics. Alternatively, a leaky capacitor fit (LCF) to the excess attenuation coefficient measurements, based on an electric energy analogy, was developed to extract a growth and decay characterization of the corresponding induced turbulence. The fit parameters are tabulated to give a complete description of the measurements, indexed by the initial pulse duration and power flux density, with distance from the pulse heater as a table parameter.
The quantum turbulence is induced in the presence of a background quantum turbulence resulting from the heaters of the second sound resonators monitoring in near real-time for the induced turbulence. This background is at steady-state, but not under experimental control.
However, as a reasonable assumption, the apparent propagation of the induced quantum turbulence trailing the second sound shock pulse is mediated by the background. The nucleation of the induced turbulence by the pulse is not considered, since the background is prenucleation. The background, established in about 350 ms and estimated to be 22 Gm/m3, is about one or two orders of magnitude larger than the induced turbulence measured.
Accounting for pulse energy by plotting energy transport fraction versus initial pulse energy, a breakpoint initial pulse energy concept is suggested. This is in contrast with a breakpoint initial pulse power discussed by previous researchers. This breakpoint energy is about 75 J/m2 in the absence of the background estimated above. Being in quiescent He II then, this is a characteristic of all second sound shock pulses. The energy dropped beyond the breakpoint appears in a dense quantum turbulence layer near the pulse heater, not significantly as the turbulence itself, but as Gorter-Mellink thermal diffusion, as a temperature gradient established in the turbulence. Consequently, this is not the induced quantum turbulence trailing the second sound shock pulses.
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