Free-fall velocities and heat transport enhancement in liquid metal magneto-convection

Vogt, Tobias; Yang, Juan-Cheng; Schindler, Felix; Eckert, Sven

doi:10.1017/jfm.2021.108

Cited by 19 publications

(39 citation statements)

References 49 publications

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“…The laboratory experiments conducted by Zürner et al (2019) for Pr = 0.029 provide Nu ∼ = (0.12 ± 0.04) × Ra (0.27±0.04) while the simulations by Scheel & Schumacher (2017) suggest Nu ∼ = (0.13 ± 0.04) × Ra (0.27±0.01) for Pr = 0.021. Recent experiments conducted in the same container by Vogt et al (2021) show a scaling of Nu = 0.166 × Ra 0.25 and thus a satisfactory agreement with the result presented here.…”

Section: Transport Of Momentum and Heatsupporting

confidence: 89%

“…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: Transport Of Momentum and Heatsupporting

confidence: 89%

Section: Experimental Set-upmentioning

confidence: 99%

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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“…In this study, the flow velocities are measured using ultrasonic Doppler velocimetry (UDV) which is an established measurement technique for opaque fluids like liquid metals (Aubert et al 2001;Brito et al 2001;Eckert & Gerbeth 2002;Gillet et al 2007;Nataf et al 2008;Vogt, Räbiger & Eckert 2014;Vogt et al 2018a,b;Zürner et al 2019Zürner et al , 2020Yang, Vogt & Eckert 2021;Vogt, Horn & Aurnou 2021a;Vogt et al 2021b). The used UDV system is a DOP3010 (from Signal Processing SA, Lausanne) equipped with 8 MHz transducers.…”

Section: Measuring Techniquementioning

confidence: 99%

Dynamics and length scales in vertical convection of liquid metals

et al. 2021

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Using complementary experiments and direct numerical simulations, we study turbulent thermal convection of a liquid metal (Prandtl number $\textit {Pr}\approx 0.03$ ) in a box-shaped container, where two opposite square sidewalls are heated/cooled. The global response characteristics like the Nusselt number ${\textit {Nu}}$ and the Reynolds number $\textit {Re}$ collapse if the side height $L$ is used as the length scale rather than the distance $H$ between heated and cooled vertical plates. These results are obtained for various Rayleigh numbers $5\times 10^3\leq {\textit {Ra}}_H\leq 10^8$ (based on $H$ ) and the aspect ratios $L/H=1, 2, 3$ and $5$ . Furthermore, we present a novel method to extract the wind-based Reynolds number, which works particularly well with the experimental Doppler-velocimetry measurements along vertical lines, regardless of their horizontal positions. The extraction method is based on the two-dimensional autocorrelation of the time–space data of the vertical velocity.

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“…Studies of HMC show that 2D rolls persist over a significant range of parameter space and can yield heat transport that is more efficient than RBC [10][11][12][13]. The flow eventually transitions to anisotropic 3D convection that can exhibit rich time dependent motions [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Quasi-static magnetoconvection with a tilted magnetic field

Nicoski¹,

Yan²,

Calkins³

2021

Preprint

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A numerical study of convection with stress-free boundary conditions in the presence of an imposed magnetic field that is tilted with respect to the direction of gravity is carried out in the limit of small magnetic Reynolds number. The dynamics are investigated over a range of Rayleigh number Ra and Chandrasekhar numbers up to Q = 2 × 10 6 , with the tilt angle between the gravity vector and imposed magnetic field vector fixed at 45 • . For a fixed value of Q and increasing Ra, the convection dynamics can be broadly characterized by three primary flow regimes: (1) quasitwo-dimensional convection rolls near the onset of convection; (2) isolated convection columns aligned with the imposed magnetic field; and (3) unconstrained convection reminiscent of nonmagnetic convection. The influence of varying Q and Ra on the various fields is analyzed. Heat and momentum transport, as characterized by the Nusselt and Reynolds numbers, are quantified and compared with the vertical field case. Ohmic dissipation dominates over viscous dissipation in all cases investigated. Various mean fields are investigated and their scaling behavior is analyzed.Provided Ra is sufficiently large, all investigated values of Q exhibit an inverse kinetic energy cascade that yields strong 'zonal' flows. Relaxation oscillations, as characterized by a quasi-periodic shift in the predominance of either the zonal or non-zonal component of the mean flow, appear for sufficiently large Ra and Q.

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Free-fall velocities and heat transport enhancement in liquid metal magneto-convection

Abstract: Abstract

Cited by 19 publications

References 49 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

Dynamics and length scales in vertical convection of liquid metals

Quasi-static magnetoconvection with a tilted magnetic field

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