The Lagrangian kinetic energy cascade in Rayleigh-B\'{e}nard convection

TL;DR

This paper investigates the kinetic energy transfer mechanisms in high Rayleigh number Rayleigh-Bénard convection, revealing a complex split cascade with both upscale and downscale energy flows using a Lagrangian approach.

Contribution

It introduces a Lagrangian framework to experimentally demonstrate a split cascade in turbulent convection, showing both upscale and downscale energy transfers.

Findings

Evidence of a split cascade with energy flowing both up and down scales.

Distinct flow topologies associated with different energy transfer directions.

Gradual transition between energy transfer regimes over a broad scale range.

Abstract

Rayleigh-B\'{e}nard convection at high Rayleigh number exhibits turbulence superimposed on large-scale circulation. While buoyancy forces drive the flow at certain scales, how kinetic energy is transfers across the scales is not understood. Here, utilizing a Lagrangian description of the kinetic energy flux, we present experimental evidence of a split cascade where energy flows downwscale at small scales and upscale at large scales. The flow topology of these energy transfer events differ profoundly, and the transition between them occurs gradually, over a broad range of scales.