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

由浮力和旋转驱动的湍流在自然界和技术中无处不在。在这个项目中，我们将基于直接数值模拟，研究不同长宽比的圆柱体中的旋转Rayleigh-Benard对流(RRBC)，从线性壁模的开始到旋转热对流的地转机制，这在几乎所有的地球物理和天体物理系统中都是非常重要的。我们的研究将把在整体对流爆发之前出现的线性壁模状态与边界纬向流(BZF)联系起来，边界纬向流在地转区与湍流整体对流共存。我们将研究全球流动结构的演变，将其作为对流开始时所有理论上可能的流动本征模的展开。通过跟踪系统中长度和时间尺度的演变、流动动力学的变化以及热和动量输运的变化，我们将量化不同的流动特征并对其进行分析，最终能够模拟和定量地预测与壁模和bzf相关的漂移频率、典型长度和速度尺度以及与不同Rayleigh、Prandtl、Ekman和Froude数相关的热输运。阐明壁模和BZF的热传输贡献及其对全球流动动力学的影响，对于在实验室实验中以及在地球物理和天体物理尺度上理解受限容器中RBC的地转状况是至关重要的。

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.