不连续的过渡到活跃的阴性流
Malcolm Hillebrand1,2,3, Ricard Alert4,5,6,7,8,9
1Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.
Nature communications
|December 15, 2025
概括
在活性流体中,过渡到活性流是不连续的,在层状和混乱的流量状态之间,速度和双稳定性突然跳跃. 这与在封闭系统中观察到的连续过渡形成鲜明对比.
科学领域:
- 物理 物理学 物理
- 流体动力学 流体动力学
- 软物质物理学 软物质物理学
背景情况:
- 活性流体在低雷诺兹数时表现出混乱的流动,称为活性流.
- 活跃流的统计性质已被理解,但从层状流向流的过渡仍然不清楚.
研究的目的:
- 在无边界,无缺陷的活体体质中,研究从层状流向流的过渡.
- 描述这种过渡的性质,无论是连续的还是不连续的.
主要方法:
- 一个最小模型的模拟,用于活跃的敌人.
- 分析平均平方速度,双稳定性,歇斯底里和有限时间的利亚普诺夫指数.
主要成果:
- 过渡到活跃的流是不连续的,标志着平均平方速度的跳跃.
- 观察了层状流和混沌流之间的双位性和歇斯底里.
- 为过渡确定了一个关键活动号码 (A* ≈ 4900).
- 在过渡的下方发生导致振荡和长时间混沌过渡的亚临界分叉.
结论:
- 在无边界的活体体质中,过渡到活跃流是不连续的.
- 斯托克斯流中的远程水力动力相互作用可能会抑制流状态的空间共存,导致不连续的过渡.
- 这些发现与封闭系统中的连续过渡形成鲜明对比.
相关概念视频
01:28Magnetostatic Boundary Conditions
1.6K
An electric field suffers a discontinuity at a surface charge. Similarly, a magnetic field is discontinuous at a surface current. The perpendicular component of a magnetic field is continuous across the interface of two magnetic mediums. In contrast, its parallel component, perpendicular to the current, is discontinuous by the amount equal to the product of the vacuum permeability and the surface current. Like the scalar potential in electrostatics, the vector potential is also continuous...
1.6K
01:24Turbulent Flow
632
Turbulent flow is characterized by unpredictable fluctuations in velocity and pressure, which result in a chaotic fluid movement distinct from the orderly patterns of laminar flow. While laminar flow is governed by smooth, parallel layers with minimal mixing, turbulent flow exhibits highly irregular, three-dimensional patterns. This behavior arises due to instabilities in the fluid's velocity profile, and amplifies as the flow velocity increases. Minor disturbances, known as turbulent...
632
01:07Laminar and Turbulent Flow
10.5K
Fluid dynamics is the study of fluids in motion. Velocity vectors are often used to illustrate fluid motion in applications like meteorology. For example, wind—the fluid motion of air in the atmosphere—can be represented by vectors indicating the speed and direction of the wind at any given point on a map. Another method for representing fluid motion is a streamline. A streamline represents the path of a small volume of fluid as it flows. When the flow pattern changes with time, the...
10.5K
01:16Electrostatic Boundary Conditions
899
Consider an external electric field propagating through a homogeneous medium. When the electric field crosses the surface boundary of the medium, it undergoes a discontinuity. The electric field can be resolved into normal and tangential components. The amount by which the field changes at any boundary is given by the difference between the field components above and below the surface boundary.
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
899
01:17Steady, Laminar Flow Between Parallel Plates
755
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.
755
01:18Boundary Layer Characteristics
503
When a fluid encounters a solid surface, a boundary layer forms due to the interaction between the fluid's motion and the stationary surface. This phenomenon is characterized by a thin region adjacent to the surface where viscous forces dominate, influencing the fluid's velocity profile. The development of the boundary layer begins at the leading edge of the surface and evolves as the fluid moves downstream.As the fluid flows over the surface, friction between the fluid and the wall slows down...
503