Abstract：
Turbulent flows are observed in low-Reynolds active fluids, which display similar phenomenology to the classical inertial turbulence but are of a different nature. Understanding the dependence of this new type of turbulence on dimensionality is a fundamental challenge in non-equilibrium physics. Real-space structures and kinetic energy spectra of bacterial turbulence are experimentally measured from two to three dimensions. The turbulence shows three regimes separated by two critical confinement heights, resulting from the competition of bacterial length, vortex size and confinement height. Meanwhile, the kinetic energy spectra display distinct universal scaling laws in quasi-2D and 3D regimes, independent of bacterial activity, length, and confinement height, whereas scaling exponents transition in two steps around the critical heights. The scaling behaviors are well captured by the hydrodynamic model we develop, which employs image systems to represent the effects of confining boundaries. The study suggests a framework for investigating the effect of dimensionality on non-equilibrium self-organized systems.
摘要：
在低雷诺活性流体中观察到湍流，表现出与经典惯性湍流相似的现象学，但性质不同。理解这种新型湍流对维度的依赖性是非平衡物理学中的一个基本挑战。从二维到三维实验测量了细菌湍流的实空间结构和动能谱。湍流显示了三个由两个临界限制高度隔开的状态，由于细菌长度的竞争，涡流的大小和限制高度。同时,动能谱在准2D和3D状态下显示出不同的通用标度定律，独立于细菌活动，长度,和禁闭高度，而缩放指数在临界高度周围分两步过渡。我们开发的水动力学模型很好地捕获了缩放行为，它采用图像系统来表示限制边界的效果。该研究提出了一个框架，用于研究维度对非平衡自组织系统的影响。
