HUSCAP logo Hokkaido Univ. logo

Hokkaido University Collection of Scholarly and Academic Papers >
Graduate School of Engineering / Faculty of Engineering >
Peer-reviewed Journal Articles, etc >

Transition from convection rolls to large-scale cellular structures in turbulent Rayleigh-Benard convection in a liquid metal layer

Files in This Item:
PhysRevFluids.4.033501.pdf1.84 MBPDFView/Open
Please use this identifier to cite or link to this item:

Title: Transition from convection rolls to large-scale cellular structures in turbulent Rayleigh-Benard convection in a liquid metal layer
Authors: Akashi, Megumi Browse this author
Yanagisawa, Takatoshi Browse this author
Tasaka, Yuji Browse this author →KAKEN DB
Vogt, Tobias Browse this author
Murai, Yuichi Browse this author →KAKEN DB
Eckert, Sven Browse this author
Issue Date: 8-Mar-2019
Publisher: American Physical Society (APS)
Journal Title: Physical Review Fluids
Volume: 4
Issue: 3
Start Page: 033501
Publisher DOI: 10.1103/PhysRevFluids.4.033501
Abstract: Turbulent Rayleigh-Benard convection was investigated within a liquid metal layer, Prandtl number Pr = 0.03, in a square vessel having a moderate aspect ratio, Gamma = 5. Laboratory experiments were performed at moderate Rayleigh numbers, 7.9 x 10(3) < Ra < 3.5 x 10(5). Ultrasonic velocity profiling was used to visualize the spatiotemporal flow structure in two horizontal planes, while temperature fluctuations were monitored simultaneously in the fluid layer. By using multiple ultrasonic sensors, a grid of orthogonal measurement lines was created. This configuration enabled the identification of coherent flow structures showing periodic oscillations. In particular, oscillatory roll-like structures were observed for Ra less than or similar to 6 x 10(4), while the transition to a new-found, fully three-dimensional cellular structure occurs around Ra = 7 x 10(4). The Fourier analysis of the temperature fluctuations indicates that the convection reaches the developed state of thermal turbulence at this Ra number. This cellular structure of the flow field is recognized as a representation of the large-scale circulation in thermal turbulence for the specific situation of confined convection in the rectangular vessel. The transition from laminar convection to thermal turbulence manifests itself in the occurrence of unstable intermediate regimes accompanied by a stepwise increment in the horizontal scale. We suggest scaling laws for the characteristic velocity and the dominating oscillation frequency and based on that for the horizontal length scale as a function of the Ra number. The comparison to corresponding values of characteristic length scales published for thermal convection in air in larger aspect ratios [Pr = 0.7, T. Hartlep et al., Phys. Rev. Lett. 91, 064501 (2003), A. Pandey et al., Nat. Commun. 9, 2118 (2018), and D. E. Fitzjarrald, J. Fluid Mech. 73, 693 (1976)] reveals a different Ra number dependence of the horizontal wave number.
Rights: ©2019 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

Export metadata:

OAI-PMH ( junii2 , jpcoar_1.0 )

MathJax is now OFF:


 - Hokkaido University