Thermal Waves and Heat Transfer Efficiency Enhancement in Harmonically Modulated Turbulent Thermal Convection

We study turbulent Rayleigh-Bernard convection over four decades of Rayleigh numbers 4 x 10(8) < Ra < 2 x 10(12), while harmonically modulating the temperatures of the plates of our cylindrical cell. We probe the flow by temperature sensors placed in the cell interior and embedded in the highly conducting copper plates and detect thermal waves propagating at modulation frequency in the bulk of the convective flow. We confirm the recent numerical prediction [Yang et al., Phys. Rev. Lett. 125, 154502 (2020)] of the significant enhancement of the Nusselt number and report its dependence on the frequency and amplitude of the temperature modulation of plates.

Automated summary

In this study, we investigate turbulent Rayleigh-Bernard convection across a wide range of Rayleigh numbers while harmonically modulating the temperatures of the plates in our experimental setup. By using temperature sensors placed inside the cell and embedded in highly conducting copper plates, we observe thermal waves propagating at the modulation frequency in the convective flow. Our findings confirm a recent numerical prediction of a significant enhancement of the Nusselt number and reveal its dependence on the frequency and amplitude of the temperature modulation of the plates.