Observation of helium II dissipation effects using a continuous superflow apparatus

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1979

OSTI ID:6237818

Brown, Y J

The Iordanskii-Langer-Fisher theory of the homogeneous thermal nucleation of vortex rings in superfluid helium explains, at least qualitatively, the large, temperature dependent critical velocities observed in a number of recent experiments. Most of those experiments have examined flow through arrays of hundreds of submicron sized pores at driving pressures above 0.1 dyne/cm/sup 2/ and have yielded critical velocities only about one-fifth the magnitude predicted by the ILF theory. This paper describes an experiment in which flow through a single, 10 ..mu..m diameter orifice is examined at pressure heads as low as 0.03 dyne/cm/sup 2/. Accurate velocity measurements at low pressure head are made possibe by a versatile recirculating flow cryostat capable of generating a continuous, calibrated flow of superfluid over time periods long enough to make sensitive pressure head measurements. The data thus obtained are analyzed according to a model in which vortex half-rings are inhomogeneously nucleated at the sharp-edged mouth of the flow channel. The ILF theory, appropriately modified, succeeds in explaining most of the important features of the data.

• Research Organization: Virginia Univ., Charlottesville (USA)
• OSTI ID: 6237818
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CONTROL EQUIPMENT
CRITICAL VELOCITY
CRYOSTATS
DATA
EQUIPMENT
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
FLUID FLOW
FLUIDS
HELIUM 4
HELIUM II
HELIUM ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL MODELS
NUCLEI
NUMERICAL DATA
QUANTUM FLUIDS
STABLE ISOTOPES
SUPERFLUIDITY
THERMOSTATS
ULTRALOW TEMPERATURE
VELOCITY
VORTEX FLOW