Non-Oberbeck-Boussinesq effects in rotating Rayleigh-Bénard convection

Abstract

We present results from Direct Numerical Simulations of rotating Rayleigh-B\'enard convection in a cylindrical cell with unity aspect ratio for water with a Prandtl number of $Pr = 4.38$ and glycerol with $Pr = 2547.9$ with a special focus on temperature dependent material properties and thus not within the framework of the conventionally used Oberbeck-Boussinesq (OB) approximation. The generated turbulent flow fields are analysed with respect to the deviations from the OB cases. For the non-Oberbeck-Boussinesq cases we obtain a breakdown of the top-bottom symmetry, that is different boundary layer thicknesses, asymmetric velocity flow patterns and modified mean temperature profiles including an increase of the centre temperature and in the case of rotation a diminished temperature gradient within the bulk. Furthermore we find a slightly different scaling of the Nusselt number with the Rayleigh as well as with the Rossby number.