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Convection patterns in a liquid metal under an imposed horizontal magnetic field

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Title: Convection patterns in a liquid metal under an imposed horizontal magnetic field
Authors: Yanagisawa, Takatoshi Browse this author
Hamano, Yozo Browse this author
Miyagoshi, Takehiro Browse this author
Yamagishi, Yasuko Browse this author
Tasaka, Yuji Browse this author →KAKEN DB
Takeda, Yasushi Browse this author
Issue Date: 30-Dec-2013
Publisher: American Physical Society (APS)
Journal Title: Physical Review E
Volume: 88
Issue: 6
Start Page: 063020
Publisher DOI: 10.1103/PhysRevE.88.063020
PMID: 24483570
Abstract: We performed laboratory experiments of Rayleigh-Bénard convection with liquid gallium under various intensities of a uniform imposed horizontal magnetic field. An ultrasonic velocity profiling method was used to visualize the spatiotemporal structure of the flows with simultaneous monitoring of the temperature fluctuations in the liquid gallium layer. The explored Rayleigh numbers Ra range from the critical value for onset of convection to 105; the Chandrasekhar number Q covers values up to 1100. A regime diagram of the convection patterns was established in relation to the Ra and Q values for a square vessel with aspect ratio 5. We identified five flow regimes: (I) a fluctuating large-scale pattern without rolls, (II) weakly constrained rolls with fluctuations, (III) a continuous oscillation of rolls, (IV) repeated roll number transitions with random reversals of the flow direction, and (V) steady two-dimensional (2D) rolls. These flow regimes are classified by the Ra/Q values, the ratio of the buoyancy to the Lorentz force. Power spectra from the temperature time series indicate that regimes I and II have the features of developed turbulence, while the other regimes do not. The region of steady 2D rolls (Busse balloon) extends to high Ra values in the present setting by a horizontal magnetic field and regime V is located inside the Busse balloon. Concerning the instabilities of the steady 2D rolls, regime III is the traveling wave convection developed from the oscillatory instability. Regime IV can be regarded as a state of phase turbulence, which is induced by intermittent occurrences of the skewed-varicose instability.
Rights: ©2013 American Physical Society
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 田坂 裕司

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