Prandtl-number dependence of interior temperature and velocity fluctuations in turbulent convection.
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.
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Center for Nonlinear Studies and Condensed Matter & Thermal Physics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
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