论文标题
三维湍流中的涡流建模和极端循环事件的拓扑结构
Eddy-Viscous Modeling and the Topology of Extreme Circulation Events in Three-Dimensional Turbulence
论文作者
论文摘要
我们讨论了特定速度场构型的作用 - 简称instantons，这些配置应在发生极端湍流事件的情况下占主导地位。为均质和各向同性湍流的随机水动力设置而设计的激体方程应用于直接数值模拟结果的解释。通过这种方式，我们能够通过涡流现象学和精确的插入式激发量的结合使用来模拟广泛尺度的极端循环事件的时间演变。尽管这种方法在流通Instantons的核心方面非常有效，但它无法描述它们的尾巴。为了克服这一困难，我们提出了对轴对称激体方程的数值处理。然后发现循环Instantons具有令人惊讶的拓扑结构，该结构由一个配对的反旋转涡流环组成，该系统围绕背景轴对称涡流流的对称轴的中心。
We discuss the role of particular velocity field configurations -- instantons, for short -- which are supposed to dominate the flow during the occurrence of extreme turbulent circulation events. Instanton equations, devised for the stochastic hydrodynamic setup of homogeneous and isotropic turbulence, are applied to the interpretation of direct numerical simulation results. We are able in this way to model the time evolution of extreme circulation events for a broad range of scales, through the combined use of eddy viscosity phenomenology and exact creeping instantons. While this approach works well for the core of circulation instantons, it fails to describe their tails. In order to overcome this difficulty, we put forward a numerical treatment of the axisymmetric instanton equations. Circulation instantons are then found to have a surprising topological structure, which consists of a system of paired counter-rotating vortex rings centered around the symmetry axis of a background axisymmetric vortical flow.
