论文标题
亚临界流中湍流增殖的机制
Mechanism for turbulence proliferation in subcritical flows
论文作者
论文摘要
在管道流中发生的湍流的亚临界过渡被认为通常是定向渗透普遍性类别中的相变。它的核心是局部湍流结构的衰减速率和增殖速率之间的平衡，该结构称为管道流动中的泡芙。在这里，我们提出了有史以来的第一个动力学机制，用于泡芙增殖 - 粉扑分为两个的过程。在我们机制的第一阶段，粉扑扩展到sl骨。在第二阶段，在湍流核心内形成了层流间隙。引入了分裂状态的概念，介导了从单个泡芙到两个泡芙状态的过渡，并预测了其形式。讨论了波动在过渡的两个阶段的作用，以及如何通过增加雷诺数来抑制分裂。使用数值模拟，该机制在随机Barkley模型中得到了验证。讨论了测试管道和其他壁界流中提出的机制的具体预测，并讨论了对定向渗透图片的普遍性的影响。
The subcritical transition to turbulence, as occurs in pipe flow, is believed to generically be a phase transition in the directed percolation universality class. At its heart is a balance between the decay rate and proliferation rate of localized turbulent structures, called puffs in pipe flow. Here we propose the first-ever dynamical mechanism for puff proliferation -- the process by which a puff splits into two. In the first stage of our mechanism, a puff expands into a slug. In the second stage, a laminar gap is formed within the turbulent core. The notion of a split-edge state, mediating the transition from a single puff to a two puff state, is introduced and its form is predicted. The role of fluctuations in the two stages of the transition, and how splits could be suppressed with increasing Reynolds number, are discussed. Using numerical simulations, the mechanism is validated within the stochastic Barkley model. Concrete predictions to test the proposed mechanism in pipe and other wall bounded flows, and implications for the universality of the directed percolation picture, are discussed.
