Spectra and statistics of velocity and temperature fluctuations in turbulent convection

Abstract

Direct measurements of the velocity in turbulent convection of $SF_6$ near its gas-liquid critical point by light scattering on the critical density fluctuations were conducted. The temperature, velocity and cross frequency power spectra in a wide range of the Rayleigh and Prandtl numbers show scaling behaviour with indices, which are rather close to the Bolgiano-Obukhov scaling in the wavenumber domain. The statistics of the velocity fluctuations remains Gaussian up to the Reynolds numbers $10^5$.