Critical Velocity of Superflow in Liquid Helium II

1952 ◽  
Vol 85 (6) ◽  
pp. 1044-1045 ◽  
Author(s):  
H. M. Fried ◽  
P. R. Zilsel
Keyword(s):  
Liquid Helium ◽  
Critical Velocity ◽  
Helium Ii

The angular acceleration of liquid helium II

1957 ◽  
Vol 250 (980) ◽  
pp. 359-385 ◽  
Keyword(s):  
Liquid Helium ◽  
Critical Velocity ◽  
Past History ◽  
Angular Acceleration ◽  
Mutual Friction ◽  
Helium Ii ◽  
Direct Measurements ◽  
History Of ◽  
Quantitative Results ◽  
Flow Experiments

Direct measurements have been made of the torques required to produce angular acceleration and retardation of liquid helium II contained in a can filled with closely spaced disks at a temperature of 1.27°K. The acceleration and retardation processes are not equivalent, and it is suggested that this asymmetry is due to the presence of vortex lines in the uniformly rotating superfluid. It is found that the forces producing superfluid acceleration are dependent on the past history of the helium and are greatly enhanced if the disk surfaces are roughened; furthermore, the superfluid flow shows a strong tendency to be macroscopically irrotational during retardation. These properties suggest that the forces are associated with turbulence in the superfluid, and it is found that a consistent description of the results can be given in terms of a mutual friction due to such turbulence. Values of the mutual friction appropriate to a steady flow are deduced and found to be in good agreement with values deduced from the results of other isothermal flow experiments; they can be represented, above a critical velocity, by a modification of the law introduced by Gorter & Mellink (1949), namely Fsn = A p sp n with A=23+/-2 posie -1 . V 0 =-0.6 +/- 0.2 c, s -1 Below the critical velocity a persistent current with a lifetime of at least 25 min has been observed. In the last section quantitative results on the growth and decay of turbulence in a non-equilibrium situation are presented, and laws describing the growth and decay processes are formulated.

Positive Ions in Liquid Helium II. The Critical Velocity for Creation of Vortex Rings

1968 ◽  
Vol 21 (26) ◽  
pp. 1738-1740 ◽  
Author(s):  
L. Bruschi ◽  
P. Mazzoldi ◽  
M. Santini
Keyword(s):  
Liquid Helium ◽  
Critical Velocity ◽  
Vortex Rings ◽  
Helium Ii ◽  
Positive Ions

scholarly journals On the Mechano-Caloric Effect in Liquid Helium II

1950 ◽  
Vol 5 (6) ◽  
pp. 1010-1013 ◽  
Author(s):  
S. Nakajima ◽  
M. Shimizu
Keyword(s):  
Liquid Helium ◽  
Helium Ii ◽  
Caloric Effect

Heat Transfer in Liquid Helium II by Internal Convection

1948 ◽  
Vol 74 (9) ◽  
pp. 1148-1156 ◽  
Author(s):  
F. London ◽  
P. R. Zilsel
Keyword(s):  
Heat Transfer ◽  
Liquid Helium ◽  
Helium Ii ◽  
Internal Convection
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