Evolution and propagation of turbulence in helium II
The purpose of this thesis was to investigate turbulence in helium II. The study begins with the decay of homogeneous isotropic turbulence created behind a sliding grid mechanism. Classical scaling arguments provide a model for the decay process which closely matches the behavior observed in this investigation. The apparent discrepancy with classical wind-tunnel studies is explained by the difference in the kinematic viscosities between air and helium II. This affects the initial growth rate of the length sale of the energy containing eddies. Classical scaling arguments with the quantized nature of superfluid vorticity also allowed direct observation of the vorticity and Kolmogorov length scale throughout the decay. Substantial differences are reported in the initial decay of counterflow turbulence and superfluid grid turbulence. Numerical simulations of counterflow turbulence suggest that this difference is tied to a redistribution of the counterflow velocity fields of the two components which must occur after the heat source is turned off. As these velocity fields become less coherent, the situation begins to resemble classical turbulence. This is supported by the data, in which the two types of turbulence appear very much alike at large times. The investigation concludes by applying helium II to the problem of propagating turbulence. A classical theory by Barenblatt (1987) suggested that a well defined turbulence front should propagate outward as h(t) [approximately] (Q[sub 0][sup 1/6]t)[sup 1/2], where Q[sub 0] is the initial energy of the turbulence. Data collected in this experiment supports Barenblatt's proposal, marking the first use of helium II in verifying a classical hydrodynamic result. In the case of turbulence propagating away from an oscillating grid however, the evidence was less conclusive. The data here could be interpreted to support either t[sup 1/3] or t[sup 1/2].
- Research Organization:
- Oregon Univ., Eugene, OR (United States)
- OSTI ID:
- 7295802
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
42 ENGINEERING
HELIUM 2
SUPERFLUIDITY
TURBULENCE
HYDRODYNAMICS
SIMULATION
WAVE PROPAGATION
FLUID MECHANICS
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MECHANICS
NUCLEI
665420* - Superfluidity- (1992-)
420400 - Engineering- Heat Transfer & Fluid Flow