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2022 Fiscal Year Final Research Report

Heat and mass transport process in the Earth's liquid core viewed from quantitative visualization experiments of thermal convection in a liquid metal layer

Research Project

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Project/Area Number 20K04114
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Review Section Basic Section 17040:Solid earth sciences-related
Research InstitutionMeisei University

Principal Investigator

Kumagai Ichiro  明星大学, 理工学部, 教授 (50597680)

Co-Investigator(Kenkyū-buntansha) 田坂 裕司  北海道大学, 工学研究院, 准教授 (00419946)
益子 岳史  静岡大学, 工学部, 准教授 (70415917)
Project Period (FY) 2020-04-01 – 2023-03-31
Keywords可視化 / 液体金属 / 熱対流 / 超音波流速分布計 / 感温液晶 / 地球 / 外核
Outline of Final Research Achievements

We have conducted Rayleigh-Benard convection experiments in a liquid metal layer at high Ra numbers aimed at understanding heat and mass transport in the Earth's fluid core. In this study, the two-dimensional temperature field on the surface of a quasi-two-dimensional liquid metal layer was obtained by a sheet of TLCs (thermochromic liquid crystals) and velocity fields inside the fluid layer were analyzed by UVPs (Ultrasonic velocity profiling). Our quantitative visualization techniques have revealed that the convective pattern strongly depends on the Ra number. While a steady circulating flow is observed at low Ra numbers, periodic oscillation of convection pattern is observed at the higher Ra numbers due to interactions between hot and cold plumes, and at the same time the irregularity of the convective motion increases with the Rayleigh number.

Free Research Field

地球惑星科学

Academic Significance and Societal Importance of the Research Achievements

本研究では、液体金属対流の2次元温度場について感温液晶シートを用いることで可視化し、また複数のUVPによる速度場計測と組み合わせることで、液体金属対流の速度場についても同時に可視化することに成功した。これにより、Prandtl数(Pr数)が1よりも十分小さな領域における対流場の変遷(Rayleigh数の増加に伴う定常的な流れから、周期性、非定常性の出現に至るまでの変遷)が明らかになった。これらの結果は、Pr数が1以上の流体で得られた現象とは異なり、低Pr数領域の熱対流による熱物質輸送の理解に役立つ成果である。工学的な応用分野においても、質の良い金属結晶の生成の際、本研究の知見が重要となる。

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Published: 2024-01-30  

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