Coordination Funds

紊流的经典图景是紊流流体运动的特征是由不同大小的旋涡和旋涡级联组成，这些旋涡和旋涡产生无特征和随机的流体运动。然而，我们的日常经验表明，自然界和技术中的湍流往往被组织成显著的大规模和长期存在的结构，这些结构可能导致极端波动。优先计划的重点是湍流上层结构，即其相干性不停留在自然尺度（如边界层高度），而是扩展到更大尺度的模式。由于测量技术、数值模拟和数学表征的重大进步，对上层建筑的研究现在成为可能。基于层析激光的测量技术可以在空间和时间上以前所未有的分辨率跟踪湍流结构的动力学。在大规模并行超级计算机上的直接数值模拟已经发展到可以在足够高的雷诺数和出现超结构的参数范围内模拟扩展域中的湍流的水平。应用数学已经发展了有效的方法来表征优势涡和流动结构，并确定其边界上的输运及其动力学演变。计算机科学为可视化和快速处理大型数据集中的结构提供了有效的算法。本优先计划的目的是综合不同的最新进展，以达到对湍流上层建筑的全面表征和理解。更详细地说，这包括上层结构的实验表征，湍流大尺度和上层结构的直接数值模拟，以及用不同的拉格朗日和欧拉方法检测和识别它们。此外，我们想从初级和次级不稳定性分析湍流上层结构的起源，对称性和边界条件对它们的形成和动力学的作用。我们想了解它们在湍流传输中的作用，特别是它们的界面。最后，我们希望开发简化模型来有效地描述它们的动力学并制定控制这些结构的策略。为了保持项目的重点，它的目的是研究单相，在简单的笛卡尔和平行几何中，由剪切或浮力驱动的壁面流动。只有通过各个学科的联合，我们才能更好地表征湍流上层结构，提取有关其基本特性的信息，从而全面了解它们对湍流统计和湍流输运的影响。

The classical picture of turbulence is that turbulent fluid motion is characterized by a cascade of vortices and swirls of different sizes that give rise to a featureless and stochastic fluid motion. Our daily experience shows, however, that turbulent flows in nature and technology are often organized in prominent large-scale and long-living structures that can cause extreme fluctuations. The focus of the Priority Programme are Turbulent Superstructures, i.e., patterns whose coherence does not stop at the natural scale, such as the boundary layer height, but extends over much larger scales. The study of superstructures is now possible due to significant advances in measurement techniques, numerical simulation, and mathematical characterization. Tomographic laser-based measurement techniques can track the dynamics of turbulent structures with unprecedented resolution in space and time. Direct numerical simulations on massively parallel supercomputers have advanced to a level where turbulent flows in extended domains can be simulated at sufficiently high Reynolds numbers and in parameter ranges where superstructures emerge. Efficient methods to characterize dominant vortices and flow structures and to determine the transport across their boundaries as well as their dynamical evolution have been developed in applied mathematics. Computer science provides efficient algorithms for the visualization and fast processing of structures in very large data sets.The aim of the present Priority Programme is to integrate the different recent advances to arrive at a comprehensive characterization and understanding of turbulent superstructures. More detailed, this includes the experimental characterization of superstructures, direct numerical simulations of turbulent large-scale and superstructures, and their detection and identification by different Lagrangian and Eulerian methods. Furthermore, we want to analyse the origin of turbulent superstructures from primary and secondary instabilities, the role of symmetries and boundary conditions for their formation and dynamics. We want to understand their role for the turbulent transport, in particular that of their interfaces. Finally, we want to develop reduced models to describe their dynamics effectively and develop strategies to control these structures. In order to keep the program focused, it is intended to study singlephase, wall-bounded flows in simple Cartesian and parallel geometries, driven by shear or buoyancy. It is only by joining forces across the various disciplines that we will be able to achieve a better characterization of turbulent superstructures, to extract information about their essential properties and thus to obtain a comprehensive understanding of their impact on turbulence statistics and turbulent transport.