Spectra and statistics of velocity and temperature fluctuations in turbulent convection

Direct measurements of the velocity in turbulent convection of SF⁶ 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 behavior with indices, which are rather close to the Bolgiano-Obukhov scaling in the wave number domain. The statistics of the velocity fluctuations remain Gaussian up to the Reynolds numbers of 10⁵.