Scattering correction and hydrodynamic drag in superleaks exhibiting varying degrees of isotropy and homogeneity
The acoustic scattering correction of several types of superleaks was measured, providing information about Kelvin inertial drag effects in the flow of superfluid helium. Al/sub 2/O/sub 3/ packed powder, Grafoil, and Grafoil foam superleaks were used. Fourth sound velocity and Doppler shift measurements were used to compare the hydrodynamic behavior of the different superleaks. A 15 cm diameter annular resonator packed with Al/sub 2/O/sub 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 lambda) 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.
- Research Organization:
- Pennsylvania State Univ., University Park (USA)
- OSTI ID:
- 5795514
- Country of Publication:
- United States
- Language:
- English
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