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.

粘性流体的湍流吸引了数百年来对其基本性质和应用的研究兴趣。但是，由于复杂性，许多未解决的问题仍然困难。相比之下，超流体中的量子湍流预计将是研究湍流性质的合适靶标，因为它的简单结构仅组成量化涡流。在本研究中，我们集中于在非常低温下超级流体氦4中量化涡旋的运动，阐明了量子湍流的动力学。为此，我们开发了一种由直径2.5μm的非常薄的超导电线制成的振荡障碍物。研究中获得的结果总结如下：1。电线振动在非常低的温度下的共振频率表明，量化为0.11.tm顺序的量化涡度附加到电线2。与电线速度相连的涡流的大小：它在层流中增加并减少湍流。3。通过在带销孔的盒子中找到一条电线，在200 mk以下填充氦气中，我们已经成功了，导致电线的振动无法产生湍流。4。量化的涡旋通过冷却通过超流体过渡并在电线和周围壁之间形成桥梁进行核核。5。桥接涡流的振动会导致超流体的湍流。通过在最近的一项研究中比较理论预测，我们包含在超流体过渡过程中涡流种子的核种子，通过振动流而生长，并最终在振动流的临界速度下变为湍流。因此，我们使用实验方法获得了阐明量化涡旋的成功。