Heat transfer scaling in natural convection with shear due to rotation

Heat transport in natural convection commonly encountered in natural and engineering flows is affected by buoyancy forces and shear. The effect of rotational shear on heat transport is examined here. Direct numerical simulation of Rayleigh-Bénard convection (RBC) with a rotating lid is performed at various rotation Reynolds numbers (Re) and Rayleigh numbers (Ra). The simulations are done for a range Ra∈[2×103,2×107] and Re∈[300,3000]. The rotating lid induces a shear into the flow resulting in two prominent flow regimes: a rotation-dominated (RD) regime and a convection-dominated (CD) regime. The RD and CD regimes are identified based on the heat transport scaling exponent of Ra. The flow topology in these two regimes is distinct, with the CD flow showing more RBC-like flow structures while the RD regime shows a central axial vortex flow. The variations of boundary layer thickness with Ra and Re also demonstrate the regimes. A parameter χ(Ra,Re) is developed to demarcate the two regimes.