TY - JOUR
T1 - Unravelling the large-scale circulation modes in turbulent Rayleigh–Bénard convection
AU - Horn, Susanne
AU - Schmid, Peter J.
AU - Aurnou, Jonathan M.
N1 - KAUST Repository Item: Exported on 2022-01-27
Acknowledgements: S.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).
PY - 2021/11/26
Y1 - 2021/11/26
N2 - The 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.
AB - The 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.
UR - http://hdl.handle.net/10754/673845
UR - https://iopscience.iop.org/article/10.1209/0295-5075/ac3da2
U2 - 10.1209/0295-5075/ac3da2
DO - 10.1209/0295-5075/ac3da2
M3 - Article
SN - 0295-5075
JO - EPL (Europhysics Letters)
JF - EPL (Europhysics Letters)
ER -