Turbulent convection in rotating slender cells

Turbulent convection in the interiors of the Sun and the Earth occurs at high Rayleigh numbers Ra, low Prandtl numbers Pr, and different levels of rotation rates. To understand the combined effects better, we study rotating turbulent convection for Pr=0.021 (for which some laboratory data corresponding to liquid metals are available), and varying Rossby numbers Ro, using direct numerical simulations in a slender cylinder of aspect ratio 0.1; this confinement allows us to attain high enough Rayleigh numbers. We are motivated by the earlier finding in the absence of rotation that heat transport at high enough Ra is similar between confined and extended domains. We make comparisons with higher aspect ratio data where possible. We study the effects of rotation on the global transport of heat and momentum as well as flow structures (a) for increasing rotation at a few fixed values of Ra, and (b) for increasing Ra(up to 10¹⁰) at the fixed, low Ekman number 1.45 × 10^-6. We compare the results with those from unity Pr simulations for the same range of Ra and Ro, and with the non-rotating case over the same range Ra of and low Pr. We find that the effects of rotation diminish with increasing Ra. These results and comparison studies suggest that for high enough Ra, rotation alters convective flows in a similar manner for small and large aspect ratios, so useful insights on the effects of high thermal forcing on convection can be obtained by considering slender domains.