Thermal convection in inclined cylindrical containers

By means of direct numerical simulations (DNS) we investigate the effect of a tilt angle β , 0 β π/2 , of a Rayleigh–Bénard convection (RBC) cell of aspect ratio 1, on the Nusselt number Nu and Reynolds number Re . The considered Rayleigh numbers Ra range from 10⁶ to 10⁸ , the Prandtl numbers range from 0.1 to 100 and the total number of the studied cases is 108. We show that the Nu\,(β)/Nu(0) dependence is not universal and is strongly influenced by a combination of Ra and Pr . Thus, with a small inclination β of the RBC cell, the Nusselt number can decrease or increase, compared to that in the RBC case, for large and small Pr , respectively. A slight cell tilt may not only stabilize the plane of the large-scale circulation (LSC) but can also enforce an LSC for cases when the preferred state in the perfect RBC case is not an LSC but a more complicated multiple-roll state. Close to β=π/2 , Nu and Re decrease with increasing β in all considered cases. Generally, the Nu(β)/Nu(0) dependence is a complicated, non-monotonic function of β .