Unravelling the large-scale circulation modes in turbulent Rayleigh–Bénard convection
KAUST DepartmentPhysical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia.
Online Publication Date2021-11-26
Print Publication Date2021-10-01
Embargo End Date2022-11-26
Permanent link to this recordhttp://hdl.handle.net/10754/673845
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AbstractThe large-scale circulation (LSC) is the most fundamental turbulent coherent flow structure in Rayleigh-B\'enard convection. Further, LSCs provide the foundation upon which superstructures, the largest observable features in convective systems, are formed. In confined cylindrical geometries with diameter-to-height aspect ratios of Γ ≅ 1, LSC dynamics are known to be governed by a quasi-two-dimensional, coupled horizontal sloshing and torsional (ST) oscillatory mode. In contrast, in Γ ≥ √2 cylinders, a three-dimensional jump rope vortex (JRV) motion dominates the LSC dynamics. Here, we use dynamic mode decomposition (DMD) on direct numerical simulation data of liquid metal to show that both types of modes co-exist in Γ = 1 and Γ = 2 cylinders but with opposite dynamical importance. Furthermore, with this analysis, we demonstrate that ST oscillations originate from a tilted elliptical mean flow superposed with a symmetric higher order mode, which is connected to the four rolls in the plane perpendicular to the LSC in Γ = 1 tanks.
CitationHorn, S., Schmid, P. J., & Aurnou, J. M. (2021). Unravelling the large-scale circulation modes in turbulent Rayleigh–Bénard convection. EPL (Europhysics Letters). doi:10.1209/0295-5075/ac3da2
SponsorsS.H. gratefully acknowledges funding by the EPSRC (grant EP/V047388/1) and J.M.A. by the NSF Geophysics Program (EAR awards 1620649 and 1853196).
JournalEPL (Europhysics Letters)