Prandtl-number dependence of interior temperature and velocity fluctuations in turbulent convection

Abstract

Temperature and vertical velocity fluctuations are measured in turbulent Rayleigh-Bénard convection at the center of an approximately unit aspect ratio container of cylindrical cross section. Our measurements show that the Rayleigh-number scaling exponent gamma of the interior temperature fluctuations (i.e., sigma(T)/deltaT approximately Ragamma) is a strong and nontrivial function of the Prandtl number in the range 2.9<Pr<12.4. Other measurements at constant Ra=2.0 x 10(9) show that the interior turbulent fluctuations decrease significantly with increasing Pr; the temperature and velocity fluctuations decrease by about approximately 45% and approximately 68% over our range in Pr.