From wall modes to the boundary zonal flow in confined rotating thermal convection

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Turbulent flows which are driven by buoyancy and rotation are omnipresent in nature and technology. In this project, based on direct numerical simulations (DNS), we will study rotating Rayleigh-Benard convection (RRBC) in cylindrical cells of different aspect ratios for a broad range of Rayleigh, Prandtl, Ekman, and Froude numbers, from the onset of the linear wall modes to the geostrophic regime of rotating thermal convection which is extremely important in almost all geophysical and astrophysical systems. Our study will connect the linear wall-mode states, which occur prior to the onset of bulk convection, with the boundary zonal flow (BZF), which coexists with turbulent bulk convection in the geostrophic regime. We will study the evolution of the global flow structure as an expansion on a full basis of all theoretically possible eigenmodes of the flow at the onset of convection. By tracking the evolution of the length and time scales, the change of the flow dynamics, and the heat and momentum transport in the system, we will quantify different flow characteristics and analyze them, and finally will be able to model and quantitatively predict the drift-frequency, typical length, and velocity scales and heat transport associated with the wall modes and the BZF, for different Rayleigh, Prandtl, Ekman, and Froude numbers. Elucidating the heat transport contributions and the effects on the global flow dynamics of the wall modes and of the BZFs is crucial for understanding the properties of the geostrophic regime of RRBC in confined containers in laboratory experiments and on the geophysical and astrophysical scales.