Rotating turbulent thermal convection at large Rayleigh numbers

与建议的项目，我们将研究旋转湍流瑞利-贝纳德对流（RBC）在非常大的瑞利数Ra互补的努力，从实验和数值模拟。 虽然我们在实验中精确测量了Ra高达1 e15的对流热传输，但模拟提供了有关内部流动结构的任何所需细节水平。 为了在实验上达到如此高的Ra，我们将使用高达19巴的压缩硫六氟化硫作为对流流体，导致大约0.8的普朗特数（Pr）。由逆Rossby数（1/Ro）表示的最大旋转速率将为约20。 其中一个主要的调查认为，旋转的影响过渡到最终的RBC状态。 由于最终状态被假定为普遍存在的分歧Ra，我们希望我们的实验室结果的合理外推到地球和天体物理相关的范围Ra和1/Ro。 另一个初步的研究将解决在地转制度的热量输送和流动结构。这是在非常高的Ra和1/Ro的制度时，压力梯度是由科里奥利力，这是占主导地位的地球大气中的直接数值模拟（DNS）将进行Ra高达1 e11与相同的几何形状的对流细胞，相同的1/Ro范围，和类似的Pr在实验中。 在数值研究中，我们特别希望研究Ekman和Stewartson边界层的结构和动力学，全球流动结构及其与环极能量平衡的密切联系，以及速度和温度波动。 此外，与数值，我们的目的是探讨制度的地转湍流。事实上，在参数空间中有一个区域，Ra从1 e9到1 e11，1/Ro从0.02到20，在那里实验和DNS重叠，并且至少在某些地方预期有地转条件。 通过实验和数值计算的互补努力，我们将为更好地理解旋转RBC在该区域的流场和热传输特性做出重要贡献。

With the proposed project we will study rotating turbulent Rayleigh-Benard convection (RBC) at very large Rayleigh numbers Ra by complementary efforts from experiments and numerical simulations. While we measure accurately the convective heat transport in the experiment for Ra up to 1e15, the simulations provide any desired level of detail about the internal flow structure. In order to reach such high Ra experimentally, we will use compressed sulfur hexafloride at up to 19 bar as the convecting fluid, resulting in a Prandtl number (Pr) of about 0.8. The maximal rotation rate as expressed by the inverse Rossby number (1/Ro) will be about 20. One of the primary investigations considers the influence of rotation on the transition to the ultimate RBC state. As the ultimate state is assumed to prevail for diverging Ra, we expect a reasonable extrapolation of our laboratory results to the geo- and astrophysically relevant ranges of Ra and 1/Ro. Another primary investigation will address the heat transport and the flow structure in the geostrophic regime. That is the regime at very high Ra and 1/Ro when pressure gradients are balanced by Coriolis forces, which is dominant in the earth's atmosphere.Direct Numerical Simulations (DNS) will be conducted for Ra up to 1e11 with the same geometry of the convection cell, the same 1/Ro-range, and similar Pr as in the experiment. In the numerical investigations, we in particular want to study the structure and dynamics of the Ekman and Stewartson boundary layers, the global flow structures and their close connection to the toroidal-poloidal energy balance, and the velocity and temperature fluctuations. Also with the numerics, we aim to explore the regime of geostrophic turbulence. In fact there is a region in the parameter space, for Ra from 1e9 to 1e11 and 1/Ro from 0.02 to 20, where experiments and DNS overlap, and where at least in some parts geostrophic conditions are expected. With the complementary efforts from both experiment and numerics, we will significantly contribute for a better understanding of the flow field and the heat transport properties in rotating RBC in this regime.