Large-eddy simulation of axial, radial and mixed centrifugal convection in a closed rotating cavity

Large-eddy simulations (LES) of centrifugal convection in a closed rotating cavity with different thermal boundary conditions are presented for Rayleigh numbers (Ra) 107∼109. Previous results for radial convection with a positive radial temperature gradient and for axial convection with low Ra are confirmed. For axial convection, turbulence develops in the core flow at Ra=109, but is considerably weaker than the turbulence for the radial and mixed convection. In mixed convection, the mean core temperature shows little radial variation as in radial convection, but has a significant axial temperature gradient as in axial convection. Compared to the radial and axial convection cases, both shroud and disc heat transfer are increased in mixed convection. Changes in disc heat transfer from the axial convection case are particularly strong. In all the conditions, laminar kinematic Ekman layers occur on the discs, but the disc thermal boundary layers for axial and mixed convection are considerably thicker.