Manipulating structures & superstructures in turbulent Rayleigh-Bénard & Taylor-Couette flow with the help of stripy wall roughness.

泰勒-库埃特(TC)流和瑞利-B-́-Enard(RB)流是流体物理学中的典型系统，前者指的是两个同轴同向或反向旋转圆柱体之间的流动，后者指的是箱内自下而上加热和冷却的流动。当驱动强度足够大时，在这两种情况下，流动都会变成湍流，在这两种情况下，结构甚至超结构都会演变，对流动的输运特性产生强烈的影响。在SPP1881程序的第一轮中，我们数值分析了剪切RB流中的换热和流动组织，并对粗糙壁上的TC流进行了数值研究，在此基础上，在本程序的第二轮中，我们希望利用空间周期壁面粗糙度(条纹)来操纵流动结构和超结构，从而控制湍流TC和剪切RB流的传递特性。这个数值项目的目的是了解热带气旋中结构的自然长度尺度与切变RB流之间的竞争，以及条状粗糙度对切变长度尺度的竞争，从而触发局部增强的羽流排放。我们的假设是，流动(超)结构能够在一定程度上遵循强加的周期，但一旦内部和外部施加的长度尺度之间的失配太大，这将不再可能。在任何情况下，通过改变条带性来调整流动的传递特性可以打开许多应用的大门。数值计算将与密切参与该项目的Roberto Verzicco密切合作，使用基于有限差分格式的超高性能代码，其中条纹状粗糙度通过浸没边界方法体现出来。TC流动的结果将与Twente湍流Taylor-Couette(T3C)设备的相应实验进行比较，在T3C设备中，我们将在圆柱体上使用条纹状砂纸粗糙度。就像在第一轮SPP1881中一样，我们将与其他几个SPP项目密切互动。在RB FLOW上，这些是奥尔加·希什金娜、埃伯哈德·博登恰茨和斯蒂芬·韦斯的作品，他们都在G̈ottingen；在TC Flow上，这些人与Bettina Frohnapfel(卡尔斯鲁厄)和Christoph Egbers(科特布斯)一起。

Taylor-Couette (TC) flow, the flow between two coaxial co- or counter-rotating cylinders, and Rayleigh-B ́enard (RB) flow, the flow in a box heated from below and cooled from above, are paradigmatic systems in physics of fluids. When driven strongly enough, in both cases the flow becomes turbulent and in both cases structures or even superstructures can evolve, strongly af- fecting the transport properties of the flow. In TC flow, these are the so-called Taylor vortices and in RB flow the convection rolls, which when laterally sheared elongate in shear direction.While in the first round of the SPP1881 program we have numerically analysed the heat transfer and flow organization in sheared RB flow and numerically studied TC flow with rough walls, building on this, in this second round of the program we want to utilize spatially periodic wall roughness (stripes) to manipulate the flow structures and superstructures and thus the transfer properties of the turbulent TC and sheared RB flow. The objective of this numerical project is to understand the competition between the natural length scale of the structures in TC and sheared RB flow with the imposed length scale by the stripy roughness, which triggers locally enhanced plume emission. Our hypothesis is that the flow (super)structures are able to follow the imposed periodicity to some degree, but once the mismatch between the internal and externally imposed length scales is too large, this will no longer be possible. In any case, the tuning of the transfer properties of the flow by modifying the stripiness can open the door to many applications.The numerical calculations will be done with a ultra-high-performance code based on a finite- difference scheme with the stripy roughness embodied through immersed boundary methods, in close collaboration with Roberto Verzicco, who is intensely involved in this project. The results for the TC flow will be compared with corresponding experiments with the Twente Turbulent Taylor-Couette (T3C) facility, where we will employ stripy sandpaper roughness at the cylinders.Just as in the first round of SPP1881, we will closely interact with several further SPP projects. On RB flow, these are those of Olga Shishkina, Eberhard Bodenschatz and Stephan Weiss, all in G ̈ottingen, and on TC flow those with Bettina Frohnapfel (Karlsruhe) and Christoph Egbers (Cottbus).