Flow topology dynamics in a three-dimensional phase space for turbulent Rayleigh-Bénard convection

F. Dabbagh, F. X. Trias, A. Gorobets, and A. Oliva
Phys. Rev. Fluids 5, 024603 – Published 28 February 2020
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Abstract

We study the flow topology dynamics in terms of the paramount nonlinearities of enstrophy and strain production at hard turbulent regimes of Rayleigh-Bénard convection (RBC). To do so, a data set of direct numerical simulations for air turbulent RBC at Rayleigh numbers Ra={108,1010,1011} is analyzed. Considering the bulk dynamics therein, the classical two-dimensional mean Lagrangian evolution of QG and RG invariants of Gu is extended to three dimensions by decomposing RG into two parts: the strain production RS and the enstrophy production tr(Ω2S). In this way, the three-dimensional phase space (QG,RS,tr(Ω2S)) allows us to identify separately the nonlinear straining and rotational mechanisms in turbulence. The main resultant observations attest that, when the turbulent regime is notably hard, a rising local self-amplification of the velocity gradient takes place in strain-dominated areas. This process is strongly aided by vortex contraction. Concomitantly, a pronounced increase in the linear contributions of vortex stretching is also identified, particularly relevant to strain-dominated slots.

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  • Received 12 April 2019
  • Accepted 28 January 2020

DOI:https://doi.org/10.1103/PhysRevFluids.5.024603

©2020 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

F. Dabbagh1,2,*, F. X. Trias1,†, A. Gorobets3,‡, and A. Oliva1,§

  • 1Heat and Mass Transfer Technological Center, ESEIAAT, Technical University of Catalonia, c/Colom 11, 08222 Terrassa, Barcelona, Spain
  • 2Christian Doppler Laboratory for Multi-Scale Modeling of Multiphase Processes, Johannes Kepler University, Altenbergerstraße 69, 4040 Linz, Austria
  • 3Keldysh Institute of Applied Mathematics of Russian Academy of Sciences, 4A Miusskaya Square, Moscow 125047, Russia

  • *firas.dabbagh@jku.at
  • xavi@cttc.upc.edu
  • andrey.gorobets@gmail.com
  • §oliva@cttc.upc.edu

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Issue

Vol. 5, Iss. 2 — February 2020

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