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渦巻く炎のエネルギー 溶融コア

物理学者は乱流対流の新たな側面を発見し、流体内で自由に移動する固体を二方向に回転させ、時には乱流によって切り替わる可能性があることを実証しました。 この研究は、地球の核から沸騰水までの流体の流れを理解することに影響を及ぼし、また、熱対流が地球内で果たす重要な役割と、固体との相互作用によって乱流が制御される可能性を強調している。



雑誌に掲載された研究 米国科学アカデミーの議事録、乱流対流、つまり下から加熱されたときの流体の動きを中心としています。

「私たちの実験は、自由に動く物体と熱対流の間の複雑な動きを明らかにしました」と、大学の数学と物理学の教授であるジュン・チャン氏は言います。[{” attribute=””>New York University and NYU Shanghai, the paper’s senior author.

The study, which also included Kaizhe Wang, a researcher in NYU’s Department of Physics, focused specifically on Rayleigh–Bénard convection—a type of convection driven by temperature differences.

Turbulence Flows Cylindrical Container

A recent experimental study, inspired by the super-rotation of the Earth’s solid core, shows when turbulence flows contained in a cylinder interact with a free body a surprisingly smooth rotation is observed. The red (warm) and blue (cold) ribbons represent water flows. Credit: Kaizhe Wang and Jun Zhang

In their experiments, conducted in the Joint Research Institute of NYU Shanghai, the paper’s authors used a cylindrical container filled with water, then heated it from the bottom, creating convective flows. The resulting turbulent flows interacted with a suspended solid (a rectangular panel) that moved freely inside the container—a setting that allowed the researchers to better study how turbulent flows interact with solid structures within.

“Surprisingly, the system becomes somewhat well-behaved,” notes Zhang. “We observed a smooth rotation of the flows and the free solid.”

Their results showed that turbulent convection-powered flows, together with the solid, can move in two directions—one clockwise and the other counterclockwise—with the co-rotational speed increasing with the intensity of the convection. More than that, their rotation can sometimes switch directions, caused by the turbulence.

“The research, inspired by the rotation of Earth’s inner core as it interacts with the convective liquid core, captures the interaction between a turbulent flow and a freely moving body within the flow,” explains Zhang. “The findings confirm that turbulence can be tamed by interacting with solids. It also reminds us that the power of thermal convection might play more important roles inside our planet Earth.”

Reference: “Persistent corotation of the large-scale flow of thermal convection and an immersed free body” by Kaizhe Wang and Jun Zhang, 15 May 2023, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2217705120


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