Effect of rotation on the temperature profile of turbulent convection with a Prandtl number $Pr = 12.3$

We report on the influence of rotation about a vertical axis on the temperature profiles and the large-scale circulations (LSC) of turbulent Rayleigh-B\'enard convection (RBC) in a cylindrical sample with aspect ratio $\Gamma = D/L = 1.00$ (D is the diameter and L the height). The working fluid was a fluorocarbon at a mean temperature $T_{m} = 25^{\circ}$C with a Prandtl number $Pr = 12.3$. The measurements covered the Rayleigh-number range $2\times 10^{10} \leq Ra \leq 2\times10^{11}$ and the inverse Rossby number range $0\leq 1/Ro \leq 9$. With weak rotation the temperature in the fluid varied as $A\times ln(z/L) + B$, where z is the distance from the bottom or top plate. For $1/Ro \geq 1.2$ we found that the temperature varied linearly with z. The temperature signature of the LSC along the sidewall was detectable up to $1/Ro \simeq 0.5$. Retrograde rotation of the LSC was observed. The LSC temperature amplitude first decreased and then remained constant up to the critical inverse Rossby number $1/Ro_c$ for the onset of Ekman-vortex formation, and then decreased again.