Global and local statistics in turbulent convection at low Prandtl numbers

Jörg Schumacher, Professor for Fluid Mechanics, Institute of Thermodynamics and Fluid Mechanics, Department of Mechanical Engineering, Technische Universität Ilmenau

Hopeman 224

Statistical properties of turbulent Rayleigh-Benard convection at low Prandtl numbers Pr, which are typical for liquid metals such as mercury or gallium (Pr ~ 0.021) or liquid sodium (Pr ~ 0.005), are investigated in high-resolution three-dimensional spectral element simulations in a closed cylindrical cell with an aspect ratio of one and compared to previous turbulent convection simulations in air for Pr=0.7. In detail, we compare the scaling of global momentum and heat transfer with convection in air. Furthermore, we analyze the intermittency in the thermal and velocity boundary layers and report scalings of skin friction and turbulent area fraction. This analysis is important in view to the transition into the ultimate regime of thermal convection.