Two-dimensional oscillation of convection roll in a finite liquid metal layer under a horizontal magnetic field

Tasaka, Yuji; Yanagisawa, Takatoshi; Fujita, Kodai; Miyagoshi, Takehiro; Sakuraba, Ataru

doi:10.1017/jfm.2020.1047

Cited by 8 publications

(5 citation statements)

References 28 publications

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“…The set-up employed for the experiments is almost identical to that used in previous studies (Tasaka et al 2016;Vogt et al 2018b;Akashi et al 2019;Tasaka et al 2021;Vogt et al 2021; to which the reader is referred for a detailed description. A noteworthy difference from our previous study (Akashi et al 2019) is that additional measuring positions for the velocity sensors have been placed at the mid-height of the fluid container in order to better compare the flow structures found here with the results reported by Vogt et al (2018a).…”

Section: Experimental Set-upmentioning

confidence: 99%

“…The thermal diffusion time for the fluid layer, t κ = H 2 /κ, is 155 s. to the description of heat transfer in the system and the measurement of temperatures and their fluctuations (Takeshita et al 1996;Cioni, Cilberto & Sommeria 1997;Segawa, Naert & Sano 1998;Horanyi, Krebs & Müller 1999;Burr & Müller 2001). The development of the ultrasonic Doppler technique for flow measurements in liquid metals (Takeda 1987;Eckert & Gerbeth 2002) enables an experimental determination of flow structures in low-Pr liquid metal convection (Cramer, Zhang & Eckert 2004;Mashiko et al 2004;Yanagisawa et al 2010Yanagisawa et al , 2013Tasaka et al 2016;Zürner et al 2019;Tasaka et al 2021;Vogt et al 2021;Yang et al 2021). This powerful technique was successfully used in the previous study by Akashi et al (2019) to identify the individual flow regimes and is also employed here.…”

Section: Experimental Set-upmentioning

confidence: 99%

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Jump rope vortex flow in liquid metal Rayleigh–Bénard convection in a cuboid container of aspect ratio

et al. 2021

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We study the topology and the temporal dynamics of turbulent Rayleigh–Bénard convection in a liquid metal with a Prandtl number of 0.03 located inside a box with a square base area and an aspect ratio of $\varGamma = 5$ . Experiments and numerical simulations are focused on the Rayleigh number range $6.7 \times 10^{4} \leqslant Ra \leqslant 3.5 \times 10^{5}$ , where a new cellular flow regime has been reported previously (Akashi et al., Phys. Rev. Fluids, vol. 4, 2019, 033501). This flow structure shows symmetries with respect to the vertical planes crossing at the centre of the container. The dynamic behaviour is dominated by strong three-dimensional oscillations with a period length that corresponds to the turnover time. Our analysis reveals that the flow structure in the $\varGamma = 5$ box corresponds in key features to the jump rope vortex structure, which has recently been discovered in a $\varGamma = 2$ cylinder (Vogt et al., Proc. Natl Acad. Sci. USA, vol. 115, 2018, pp. 12674–12679). While in the $\varGamma = 2$ cylinder a single jump rope vortex occurs, the coexistence of four recirculating swirls is detected in this study. Their approach to the lid or the bottom of the convection box causes a temporal deceleration of both the horizontal velocity at the respective boundary and the vertical velocity in the bulk, which in turn is reflected in Nusselt number oscillations. The cellular flow regime shows remarkable similarities to properties commonly attributed to turbulent superstructures.

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Section: Experimental Set-upmentioning

confidence: 99%

Section: Experimental Set-upmentioning

confidence: 99%

Jump rope vortex flow in liquid metal Rayleigh–Bénard convection in a cuboid container of aspect ratio

et al. 2021

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“…2) suggest that these surfaces are not at the same temperature, though the resulting thermal gradient is probably too small to counterbalance the edge-to-centre mass transport. The latter phenomenon could originate from convection rolls generated by the intense magnetic field coming from the RF heating [8,9]. Such rolls would transport C more efficiently than the thermal gradient would do, as evidenced in liquid phase SiC growth experiments [10].…”

Section: Resultsmentioning

confidence: 98%

Liquid Si-Induced 4H-SiC Surface Structuring Using a Sandwich Configuration

Jousseaume

Cauwet

Ferro

2022

MSF

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In view of obtaining a step bunched morphology on large 4H-SiC surfaces, a sandwich configuration is investigated. A piece of silicon is melted between two 4H-SiC 4° off wafers, allowing a better spreading of the liquid than a Si drop approach. This successfully leads to highly step-bunched surfaces, though with irregular steps. The most regular step and terrace stuctures were found to be the result of epitaxial growth via a dissolution-precipitation process occuring from the edges to the center of the wafers. This is probably caused by radio-frequency induced electromagnetic convection within liquid Si. This process is quenched when using smaller liquid thickness.

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“…Of course, the thickness values considered in the present work are probably too small for buoyancy-induced convection. However, a strong electromagnetic field, such as the one present inside our RF heated reactor, could activate such a turbulent flow [7,8]. This is because of the high electrical conductivity of liquid Si which makes it easily subjected to induced currents and thus to electromagnetic convection.…”

Section: Resultsmentioning

confidence: 99%

Transport Phenomena during Liquid Si-Induced 4H-SiC Surface Structuring in a Sandwich Configuration

Jousseaume

Cauwet

Ferro

2023

SSP

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4H-SiC/Si(liq)/4H-SiC stacks were treated at 1550-1600°C under H2 in a RF-heated cold-wall reactor in order to generate macrosteps-structuring of the 4°off SiC(0001) wafers. Using 400 μm thick liquid Si, the observed important matter transport from the edges to the center of the same wafer was attributed to RF-induced convection rolls inside the thick liquid Si. When the liquid thickness was reduced down to 30 μm, the matter transport followed this time the vertical thermal gradient like in the case of liquid phase epitaxy. The dissolution rate of the bottom (hotter) wafer was found to increase from 1.7 μm/h at 1550°C to 3.3 μm/h at 1600°C. The use of H2 gas was found essential to the system since it does not generate gas trapping (unlike Ar) and it participates to the creation of the vertical thermal gradient.

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Two-dimensional oscillation of convection roll in a finite liquid metal layer under a horizontal magnetic field

Abstract: Abstract

Cited by 8 publications

References 28 publications

Jump rope vortex flow in liquid metal Rayleigh–Bénard convection in a cuboid container of aspect ratio

Jump rope vortex flow in liquid metal Rayleigh–Bénard convection in a cuboid container of aspect ratio

Liquid Si-Induced 4H-SiC Surface Structuring Using a Sandwich Configuration

Transport Phenomena during Liquid Si-Induced 4H-SiC Surface Structuring in a Sandwich Configuration

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