Heat transport measurements in turbulent rotating Rayleigh-Bénard convection

We present experimental heat transport measurements of turbulent Rayleigh-B\'enard convection with rotation about a vertical axis. The fluid, water with a Prandtl number (σ) of about 6, was confined in a cell with a square cross section of 7.3×7.3 cm² and a height of 9.4 cm. Heat transport was measured for Rayleigh numbers 2×10⁵<Ra<5×10⁸ and Taylor numbers 0<Ta<5×10⁹. We show the variation in normalized heat transport, the Nusselt number, at fixed dimensional rotation rate ΩD, at fixed Ra varying Ta, at fixed Ta varying Ra, and at fixed Rossby number Ro. The scaling of heat transport in the range of 10⁷ to about 10⁹ is roughly 0.29 with a Ro-dependent coefficient or equivalently is also well fit by a combination of power laws of the form a Ra1/5+b Ra1/3. The range of Ra is not sufficient to differentiate single power law or combined power-law scaling. The data are roughly consistent with an assumption that the enhancement of heat transport owing to rotation is proportional to the number of vortical structures penetrating the boundary layer. We also compare indirect measures of thermal and Ekman boundary layer thicknesses to assess their potential role in controlling heat transport in different regimes of Ra and Ta.