Turbulent superstructures in the turbulent cascade of Reynolds stresses

雷诺应力湍流级联中的湍流上部结构

• 批准号: 429326502
• 负责人: Dr.-Ing. Davide Gatti
• 金额: --
• 依托单位: Institut für Strömungsmechanik (ISTM)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/429326502?language=en
• 关键词: Turbulent; superstructures; turbulent; cascade; Reynolds

Vortical structures with different characteristic length scales coexist and interact reciprocally in wall-bounded turbulence. They range from very large-scale structures away from the wall to small-scale eddies in the wall vicinity. The large-scale motions are called turbulent superstructures - TSS in the following – and have length scales much larger than those of the near-wall vortices. TSS play an important role in the dynamics of turbulent flows, where they cause strong velocity fluctuations with a characteristic length scale of many times the largest length scale of the flow, for instance the thickness of a turbulent boundary layer. TSS are responsible for a significant fraction of total turbulent kinetic energy and increased friction drag at the wall, through their contribution to the Reynolds shear stress. Presently, no agreed-upon description of the dynamics of TSS exists, especially concerning their mutual interaction with other scales. While the effect of TSS on the small scale structures at the wall has been documented in literature, there is contrasting evidence regarding an influence in the opposite direction, i.e. an influence of the small scale structures onto the TSS. In particular, it is still unclear whether the small scale structures play a determinant role in the origin of TSS. Understanding the mutual influence of TSS and the other scales of the flow is of great importance not only from a theoretical point of view, but also because it greatly affect our ability to model and control a turbulent flow.In the present proposal we investigate the interaction between TSS and the other smaller scale structures of the flow. We apply a new theoretical framework, the Anisotropic Generalized Kolmogorov Equations, in order to describe how the separate component of the Reynolds stress tensor are produced, dissipated and transported through structures at different length scales and across physical space in the turbulent flow. In this framework, the result of the interaction between scales is a measurable transport of Reynolds stresses across scales and space, that constitutes the so-called turbulent cascade of Reynolds stresses.We develop a series of numerical experiments, in which the physics of turbulent flows in channels is let develop naturally or purposely altered, in order to highlight or quench some aspects of TSS. Through an analysis of how Reynolds stresses are transported through different scales, we can highlight the relationship between TSS and other structures of the turbulent flow.

具有不同特征长度尺度的涡流结构并存并在壁结合的湍流中相互相互作用。它们的范围从非常大的结构从墙壁到墙附近的小规模涡流。大规模的运动称为湍流上层建筑 - TSS在以下内容中 - 长度比近壁涡旋的尺度大得多。 TSS在湍流的动力学中起着重要的作用，在湍流的动力学中，它们会引起强速度波动，其特征长度尺度是流量最大的最大长度尺度，例如湍流边界层的厚度。 TSS通过对Reynolds剪切应力的贡献，造成总湍流动能的很大一部分，并增加了壁上的摩擦阻力。目前，对TSS动力学的描述尚无同意的描述，尤其是关于它们与其他量表的相互作用。尽管在文献中已经记录了TSS对壁上小规模结构的影响，但存在相反方向的影响的证据，即小规模结构对TSS的影响。特别是，尚不清楚小规模结构在TSS的起源中是否起着确定的作用。了解TSS和流动的其他量表的相互影响不仅从理论的角度来看非常重要，而且还因为它很大程度上影响了我们建模和控制湍流的能力。在当前的建议中，我们研究了TSS与流量的其他较小规模结构之间的相互作用。我们应用了一个新的理论框架，即各向异性广义的kolmogorov方程，以描述雷诺德应力张量的单独组件如何产生，消散和通过不同长度的结构，以及在湍流中的物理空间跨物理空间进行运输。在这个框架中，量表之间相互作用的结果是雷诺的可测量运输压力跨尺度和空间，构成了雷诺的所谓湍流级联压力。我们发展了一系列的数值实验，其中，通道中的湍流物理学使自然或有目的地改变或有目的地改变了某些方面的临时或构成临时的仪式。通过分析雷诺应力如何通过不同的尺度运输，我们可以强调TSS与湍流的其他结构之间的关系。