| Project/Area Number |
17540335
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | OSAKA CITY UNIVERSITY |
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Principal Investigator |
YANO Hideo Osaka City University, Graduate School of Science, Associate Professor, 大学院理学研究科, 助教授 (70231652)
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| Co-Investigator(Kenkyū-buntansha) |
HATA Tohru Osaka City University, Graduate School of Science, Professor, 大学院理学研究科, 教授 (10156333)
OBARA Ken Osaka City University, Graduate School of Science, Lecturer, 大学院理学研究科, 講師 (50347481)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2006: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2005: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Keywords | 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 |
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| Research Abstract |
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.
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