Boundary layers in turbulent Rayleigh-B\'enard convection in air

TL;DR

This study visualizes the boundary layer flow in turbulent Rayleigh-Bénard convection in air at high Rayleigh number, revealing transient, coherent structures and turbulence development influenced by large-scale circulation.

Contribution

The paper provides direct visualization of boundary layer dynamics in turbulent convection at high Rayleigh number, highlighting transient coherent structures and turbulence onset.

Findings

Boundary layer is highly transient with evolving coherent structures.

Turbulence develops where large-scale circulation interacts with the boundary.

Boundary layer behavior varies with position on the heating plate.

Abstract

The boundary layer flow in a Rayleigh-B\'enard convection cell of rectangular shape has been visualized in this fluid dynamics video. The experiment has been undertaken in air at a Rayleigh number $Ra=1.3\times 10^{10}$ and a Prandtl number $Pr=0.7$. Various sequences captured at selected positions of the heating plate show that the boundary layer is a very transient flow region characterized by coherent structures that permanently evolve. It becomes fully turbulent in the areas where the large-scale circulation impinge or leave the bottom plate.