Generation of Quantized Vortices in Alternating Flows of Superfluid Helium 4

超流氦 4 交变流动中量子化涡流的产生

基本信息

批准号：
17540335
负责人：
YANO Hideo
金额：
$ 2.3万
依托单位：
OSAKA CITY UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540335/
关键词：
superfluid helium quantized vortex quantum turbulence laminar flow turbulent flow turbulence transition vibrating wire 超流動乱流振動子希釈冷凍機

项目摘要

Turbulent flow of viscous fluids has attracted research interests on both its basic nature and application for centuries; however, many unresolved problems still remain with difficulties because of complexity. In contrast, quantum turbulence in a superfluid is expected to be a suitable target for studying the nature of turbulence, because of its simple structure consisting only quantized vortices. In the present study, we have concentrated on the motion of quantized vortices in superfluid helium 4 at very low temperature, elucidating dynamics of quantum turbulence. For this purpose, we developed an oscillating obstacle made of a very thin superconducting wire with a 2.5 μm diameter. Results obtained in the study are summarized as follows:1. Resonance frequency of wire vibration at very low temperature suggests that quantized vortices of a size of 0.11.tm order are attached to the wire.2. The size of vortices attached to a wire varies with wire velocity: it increases in a laminar flow and decreases in a turbulent flow.3. We have succeeded in a condition for which vibration of a wire is unable to generate turbulence, by locating a wire in a box with a pin hole and filling helium below 200 mK for 20 hours.4. Quantized vortices are nucleated by cooling through the superfluid transition and form bridges between a wire and a surrounding wall.5. Vibration of the bridged vortices causes turbulence in the superfluid. By comparing a theoretical prediction in a recent study, we conclude that vortex seeds nucleate during the superfluid transition, grow by vibrating flows, and eventually become turbulence at a critical velocity of the vibrating flow. Consequently, we obtained success of elucidating generation of quantized vortices using an experimental method.

几个世纪以来，粘性流体的湍流一直吸引着对其基本性质和应用的研究兴趣；然而，由于其复杂性，许多未解决的问题仍然存在困难，相比之下，超流体中的量子湍流有望成为研究粘性流体湍流的合适目标。湍流的本质，因为其结构简单，仅由量子化涡流组成。在本研究中，我们集中研究超流氦 4 中非常低的量子化涡流的运动。为此，我们开发了一种由直径为 2.5 μm 的超细导线制成的振荡障碍物，研究结果总结如下： 1．温度表明，0.11.tm 量级的量子化涡流附着在导线上。2. 附着在导线上的涡流大小随导线速度而变化：它会增加。 3. 我们成功地解决了线的振动无法产生湍流的情况，方法是将一根线放置在一个带有针孔的盒子中，并在 200 mK 以下的温度下充入氦气 20 小时。 4. 量子化涡流通过超流体过渡冷却而成核，并在导线和周围壁之间形成桥。5. 桥接涡流的振动。通过比较最近研究中的理论预测，我们得出结论，涡流种子在超流体转变过程中成核，通过振动流生长，并最终在所检查的振动流的临界速度下变成湍流，我们取得了成功。使用实验方法阐明量子化涡旋的产生。