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

Abstract

We study turbulent Rayleigh-Bénard convection over four decades of Rayleigh numbers 4×10^{8}<Ra<2×10^{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)PRLTAO0031-900710.1103/PhysRevLett.125.154502] of the significant enhancement of the Nusselt number and report its dependence on the frequency and amplitude of the temperature modulation of plates.