论文标题
滚动式结构形成和湍流剪切流中维护的机理
Mechanism of Roll-Streak Structure Formation and Maintenance in Turbulent Shear Flow
论文作者
论文摘要
在壁结合的剪切流中，主要的相干结构是流向卷和条纹（R-S）。缺乏相关的不稳定性，R-S已归因于平均流动和扰动之间的非正常介导的相互作用。这种相互作用可能是由于瞬时增长的扰动而直接发生的，或者是由于湍流雷诺应力对R-S的稳定而间接发生的。直接和间接机制之间的基本区别是理解湍流物理的核心，是在直接机制中，R-S本身是增长的结构，而在间接机制中，R-S作为自组织结构出现。在紧急的R-S理论中，基本机制是通过雷诺（Reynolds）强调的条纹组成的，该强调配置为通过提升过程支持其相关的滚动。这要求条纹组织动荡的扰动，例如产生雷诺的压力，这些压力配置为加强条纹。在本文中，我们提供了详细的分析，从物理上解释了这种积极反馈的原因，并且是剪切流中湍流的普遍特性。还分析了与理论研究（r = 1650的poisseullle流量）相同的湍流数据的DNS数据，以验证该机制在DNS中起作用。
In wall-bounded shear flow the primary coherent structure is the streamwise roll and streak (R-S). Absent of an associated instability the R-S has been ascribed to non-normality mediated interaction between the mean flow and perturbations. This interaction may occur either directly due to excitation of a transiently growing perturbation or indirectly due to destabilization of the R-S by turbulent Reynolds stresses. A fundamental distinction between the direct and the indirect mechanisms, which is central to understanding the physics of turbulence, is that in the direct mechanism the R-S is itself the growing structure while in the indirect mechanism the R-S emerges as a self-organized structure. In the emergent R-S theory the fundamental mechanism is organization by the streak of Reynolds stresses configured to support its associated roll by the lift-up process. This requires that a streak organizes turbulent perturbations such as to produce Reynolds stresses configured to reinforce the streak. In this paper we provide detailed analysis explaining physically why this positive feedback occurs and is a universal property of turbulence in shear flow. DNS data from the same turbulent flow as that used in the theoretical study (Poisseullle flow at R=1650) is also analyzed verifying that this mechanism operates in DNS.
