Origin of the Temperature Oscillation in Turbulent Thermal Convection

TL;DR

This study investigates the origin of low-frequency temperature oscillations in turbulent thermal convection, revealing that they result from bulk flow dynamics rather than boundary layer processes, based on experimental 3D spatial analysis.

Contribution

It provides new experimental evidence that temperature oscillations in turbulent convection are driven by bulk flow motions, not boundary layer oscillations, clarifying their physical origin.

Findings

Temperature oscillations are not due to boundary layer instabilities.

Oscillations result from horizontal motion of hot and cold fluids.

Flow twisting and sloshing modulate temperature fluctuations.

Abstract

We report an experimental study of the three-dimensional spatial structure of the low frequency temperature oscillations in a cylindrical Rayleigh-B\'{e}nard convection cell. It is found that thermal plumes are not emitted periodically, but randomly and continuously, from the top and bottom plates. We further found that the oscillation of the temperature field does not originate from the boundary layers, but rather is a result of the horizontal motion of the hot ascending and cold descending fluids being modulated by the twisting and sloshing motion of the bulk flow field.