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We have studied the flow of superfluid 4 He generated by a vibrating wire. As the drive force increases, the velocity of the wire grows in the laminar-flow regime, until it suddenly drops at the onset of the turbulent-flow regime. As the drive force decreases, the turbulence disappears at a critical velocity. This result suggests that the vortices on the wire are confined within a finite size, even in turbulence. We have measured the critical velocity of seven vibrating wires, whose resonance frequencies range from 0.5 kHz to 9 kHz, at 1.4 K and found that the critical velocity is almost constant below an oscillation frequency of 2 kHz and increases above this frequency. We have also observed the response of a vibrating wire in superfluid 4 He at a low temperature of 30 mK. We find that the resonance frequency jumps upward at the same moment as the entry of the flow to a turbulent state. The frequency jump may be caused by vortex dynamics such as expansion, entanglement, and reconnection occurring in the turbulence. © 2006 American Institute of Physics.

Original publication

DOI

10.1063/1.2354663

Type

Journal article

Journal

AIP Conference Proceedings

Publication Date

01/12/2006

Volume

850

Pages

195 - 198