Univ Lyon, Ens de Lyon, Univ Claude Bernard Lyon 1, CNRS, Laboratoire de Physique, F-69342 Lyon, France.
InPhyNi, UMR CNRS 7010, Nice, France.
Phys Rev Lett. 2019 Feb 22;122(7):074502. doi: 10.1103/PhysRevLett.122.074502.
Many turbulent flows undergo drastic and abrupt configuration changes with huge impacts. As a paradigmatic example we study the multistability of jet dynamics in a barotropic beta plane model of atmosphere dynamics. It is considered as the Ising model for Jupiter troposphere dynamics. Using the adaptive multilevel splitting, a rare event algorithm, we are able to get a very large statistics of transition paths, the extremely rare transitions from one state of the system to another. This new approach opens the way for addressing a set of questions that are out of reach through direct numerical simulations. We demonstrate for the first time the concentration of transition paths close to instantons, in a numerical simulation of genuine turbulent flows. We show that the transition is a noise-activated nucleation of vorticity bands. We address for the first time the existence of Arrhenius laws in turbulent flows. The methodology we developed shall prove useful to study many other transitions related to drastic changes for the turbulent dynamics of climate, geophysical, astrophysical, and engineering applications. This opens a new range of studies impossible so far, and bring turbulent phenomena in the realm of nonequilibrium statistical mechanics.
许多湍流流动经历剧烈和突然的形态变化，产生巨大影响。作为一个典型的例子，我们研究了在正压 β 平面大气动力学模型中射流动力学的多稳定性。它被认为是木星对流层动力学的伊辛模型。我们使用自适应多层次分裂、稀有事件算法，能够得到非常大的跃迁路径统计数据，即系统从一种状态到另一种状态的极罕见跃迁。这种新方法为解决一组通过直接数值模拟无法解决的问题开辟了道路。我们首次在真正的湍流数值模拟中展示了跃迁路径集中在瞬时附近的情况。我们表明，跃迁是涡度带的噪声激活成核。我们首次解决了湍流中阿累尼乌斯定律的存在性问题。我们开发的方法将证明对研究许多其他与气候、地球物理、天体物理和工程应用的湍流动力学的剧烈变化有关的跃迁有用。这开辟了迄今为止不可能的一系列新的研究，并将湍流现象引入非平衡统计力学领域。
