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Experimental investigation of the macroscopic flow of He II due to an oscillating grid in the zero temperature limit

Research output: Contribution to Journal/MagazineJournal articlepeer-review

Published
Article number056307
<mark>Journal publication date</mark>1/01/2004
<mark>Journal</mark>Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics
Issue number5
Volume70
Number of pages1
Publication StatusPublished
<mark>Original language</mark>English

Abstract

A systematic experimental investigation of the macroscopic flow properties of extremely pure He II in the zero temperature limit is reported, covering the pressure range [Formula presented]. The flow is generated by electrostatically driven oscillations of a thin, tightly stretched, circular, square-mesh nickel grid. With growing amplitude of oscillation, the flow changes character at a first critical threshold from pure inviscid superflow past a submerged body of hydrodynamically enhanced mass, to a flow regime that is believed to involve a boundary layer composed of quantized vortex loops. Here the oscillatory motion of the grid acquires strongly nonlinear features. These include double-valued (reentrant) resonance curves and a decrease in the resonant frequency with increasing drive amplitude, but without any appreciable increase in damping. On further increase of the drive level, a second critical threshold is attained: here, the resonant frequency reaches a stable value, the response amplitude almost stops growing, but the linewidth increases. Finally, the flow acquires the character of fully developed classical turbulence, characterized by a square-root dependence of flow velocity on the driving force. Additional flow features attributable to the presence of remanent vorticity are observed and discussed.