Extreme dissipation event due to plume collision in a turbulent convection cell

Abstract

An extreme dissipation event in the bulk of a closed three-dimensional turbulent convection cell is found to be correlated with a strong reduction of the large-scale circulation flow in the system that happens at the same time as a plume emission event from the bottom plate. The reduction in the large-scale circulation opens the possibility for a nearly frontal collision of down- and upwelling plumes and the generation of a high-amplitude thermal dissipation layer in the bulk. This collision is locally connected to a subsequent high-amplitude energy dissipation event in the form of a strong shear layer. Our analysis illustrates the impact of transitions in the large-scale structures on extreme events at the smallest scales of the turbulence, a direct link that is observed in a flow with boundary layers. We also show that detection of extreme dissipation events which determine the far-tail statistics of the dissipation fields in the bulk requires long-time integrations of the equations of motion over at least hundred convective time units.

accepted for Phys. Rev. E, all figures are downsized

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• Similarities between characteristics of convective turbulence in confined and extended domains
• Connecting boundary layer dynamics with extreme bulk dissipation events in Rayleigh-Bénard flow
• Plane-layer Rayleigh-Bénard convection up to $Ra=10^{11}$: Near-wall fluctuations and role of initial conditions
• Jump rope vortex flow in liquid metal Rayleigh-Bénard convection in a cuboid container of aspect ratio five