Actions for THE SCATTERING CORRECTION AND HYDRODYNAMIC DRAG IN SUPERLEAKS EXHIBITING VARYING DEGREES OF ISOTROPY AND HOMOGENEITY (SUPERFLUIDS, ACOUSTICS, FOURTH SOUND).

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THE SCATTERING CORRECTION AND HYDRODYNAMIC DRAG IN SUPERLEAKS EXHIBITING VARYING DEGREES OF ISOTROPY AND HOMOGENEITY (SUPERFLUIDS, ACOUSTICS, FOURTH SOUND).

Author
ROTH, JAMES ANTHONY
Physical Description
147 pages
Additional Creators
Pennsylvania State University
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Summary
The acoustic scattering correction of several types of superleaks has been measured, providing information about Kelvin inertial drag effects in the flow of Superfluid Helium. Al(,2)O(,3) packed powder, Grafoil, and Grafoil foam superleaks have been used. Fourth sound velocity and Doppler shift measurements have been used to compare the hydrodynamic behavior of the different superleaks.
A 15 centimeter diameter annular resonator packed with Al(,2)O(,3) powder was used to probe the low-velocity Landau flow region of persistent currents. The Doppler shift of the sound velocity gives a value for the Kelvin drag parameter g(or (lamda)) equal to that determined from the scattering correction; g = 0.80 for this superleak having a scattering correction n = 1.12. Measurements were made both during rotation of the cryostat and with a persistent current established by rotating while cooling down from above the lambda point.
The Kelvin drag effects were too large in the Grafoil, as evidenced by a scattering correction of n = 4.41, to permit a persistent current that could be detected with the rotating cryostat constructed for these experiments.
The distribution of pore sizes for the Grafoil foam sample included sufficient large pores to allow movement of the normalfluid component. The observed scattering correction was a function of pressure, temperature, and frequency, and exhibited metastability. Values of n between 2.1 and 3.1 were obtained. No evidence of a persistent current in the foam superleak was detected.
Direct comparison of the behavior of the three superleaks showed the Al(,2)O(,3) superleak to be isotropic and homogeneous, the Grafoil superleak to be anisotropic and homogeneous, and the Grafoil foam superleak to be anisotropic and inhomogeneous.
Other Subject(s)
Dissertation Note
Ph.D. The Pennsylvania State University 1985.
Note
Source: Dissertation Abstracts International, Volume: 46-06, Section: B, page: 1974.
Part Of
Dissertation Abstracts International
46-06B
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