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Turbulent thermal superstructures in Rayleigh-Bénard convection

Richard J. A. M. Stevens, Alexander Blass, Xiaojue Zhu, Roberto Verzicco, and Detlef Lohse
Phys. Rev. Fluids 3, 041501(R) – Published 6 April 2018

Abstract

We report the observation of superstructures, i.e., very large-scale and long living coherent structures in highly turbulent Rayleigh-Bénard convection up to Rayleigh Ra=109. We perform direct numerical simulations in horizontally periodic domains with aspect ratios up to Γ=128. In the considered Ra number regime the thermal superstructures have a horizontal extend of six to seven times the height of the domain and their size is independent of Ra. Many laboratory experiments and numerical simulations have focused on small aspect ratio cells in order to achieve the highest possible Ra. However, here we show that for very high Ra integral quantities such as the Nusselt number and volume averaged Reynolds number only converge to the large aspect ratio limit around Γ4, while horizontally averaged statistics such as standard deviation and kurtosis converge around Γ8, the integral scale converges around Γ32, and the peak position of the temperature variance and turbulent kinetic energy spectra only converge around Γ64.

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  • Received 8 August 2017

DOI:https://doi.org/10.1103/PhysRevFluids.3.041501

©2018 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Richard J. A. M. Stevens1, Alexander Blass1, Xiaojue Zhu1, Roberto Verzicco1,2, and Detlef Lohse1,3

  • 1Physics of Fluids Group, Max Planck Center Twente for Complex Fluid Dynamics, J. M. Burgers Center for Fluid Dynamics, and MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
  • 2Dipartimento di Ingegneria Industriale, University of Rome “Tor Vergata,” Via del Politecnico 1, Roma 00133, Italy
  • 3Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, 37077 Göttingen, Germany

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Issue

Vol. 3, Iss. 4 — April 2018

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