LAUSR

Abstract Turbulent thermal convection was numerically investigated in a cubic cavity under homogeneous and inhomogeneous heating for Rayleigh number Ra = 10 7 and Prandtl number Pr = 6.46 . Inhomogeneous heating was created only at the lower boundary using mixed boundary conditions. Three configurations of the heated regions distribution of the same heating area were considered. The total heat flux through the lower boundary substantially depends on the distribution of the heated regions and increases with decreasing of the heaters size, which is in a good agreement with Ripesi et al., 2014 and Bakhuis et al., 2018. It was found that in turbulent thermal convection under inhomogeneous boundary conditions large-scale circulation (LSC) is formed. Dynamics and structure of LSC strongly depends on the distribution of conducting regions. In case of Rayleigh-Benard convection, the main flow is more complex with higher-order modes prevailing. Time-averaged velocity field revealed the existence of two vortex rings rotating in opposite directions and located near horizontal walls. Decomposing the velocity into free-slip modes allowed us to find that these vortex rings are stable and provide the most of system energy. The absence of mean LSC results in a specific convective heat transfer mechanism when mean and turbulent heat fluxes are spatially separated.