论文标题
准二维湍流中大规模动力学的双重动力学
Bistability of the large-scale dynamics in quasi-two-dimensional turbulence
论文作者
论文摘要
在许多地球物理和天体物理流动中，沿流动的一个方向抑制波动驱动了学能量的准2D高档通量，从而导致形成最大尺度的强涡流冷凝物。最近的研究表明，向这种冷凝水状态的过渡是滞后的，导致有限的双向范围，在这种范围内，冷凝水状态以及常规3D状态都可以在相同的参数值中存在。在这项工作中，我们使用薄层流的直接数值模拟来研究该双重范围是否随着域的大小和湍流强度的增加而生存。通过研究从一个状态到另一个状态发生罕见过渡的时间尺度，我们发现，随着盒子的大小和/或雷诺数的增加，双态范围会增加，这表明双稳定性既不是有限尺寸，也不是有限的效果。此外，我们预测从低箱尺寸的双峰状态的交叉，低框大小的纯磁滞状态，高RE，在任何有限的时间尺度上都禁止从一个状态到另一个状态的任何过渡。
In many geophysical and astrophysical flows, suppression of fluctuations along one direction of the flow drives a quasi-2D upscale flux of kinetic energy, leading to the formation of strong vortex condensates at the largest scales. Recent studies have shown that the transition towards this condensate state is hysteretic, giving rise to a limited bistable range in which both the condensate state as well as the regular 3D state can exist at the same parameter values. In this work, we use direct numerical simulations of thin-layer flow to investigate whether this bistable range survives as the domain size and turbulence intensity are increased. By studying the time scales at which rare transitions occur from one state into the other, we find that the bistable range grows as the box size and/or Reynolds number Re are increased, showing that the bistability is neither a finite-size nor a finite-Re effect. We furthermore predict a crossover from a bimodal regime at low box size, low Re to a regime of pure hysteresis at high box size, high Re, in which any transition from one state to the other is prohibited at any finite time scale.
