Dispersion of run-and-tumble microswimmers through disordered media
Dispersion of run-and-tumble microswimmers through disordered media
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通过无序介质分散奔跑翻滚的微型游泳者
DOI：
10.1103/physreve.108.064608
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发表时间：
2023
影响因子：
2.4
通讯作者：
Saintillan, David
中科院分区：
文献类型：
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作者：
Saintillan, David
了解微生物和自推进颗粒在多孔介质中的运输特性对人类健康和微生物生态学具有重要意义。在自由空间中，由于自我推进和方向去相关机制（如奔跑和翻滚动力学或旋转扩散）的相互作用，大多数微游泳者进行扩散随机游动。在非结构化多孔介质中，与微观结构的碰撞导致粒子的有效空间扩散系数从其自由空间值下降。在这里，我们分析了一个简单的模型系统，该系统由非相互作用的点粒子组成，在由随机分布的圆形障碍物组成的二维无序介质中进行奔跑和翻滚动力学，在没有布朗扩散或流体动力相互作用的情况下。假设这些粒子以硬球体的形式与障碍物碰撞，然后在保持其方向的同时在障碍物表面无摩擦阻力地滑动，直到它们逃脱或翻滚。我们表明，长时间扩散系数的变化可以用一个通用的无量纲障碍函数来描述，该函数是由障碍物面积分数和pceclet数组成的，或者是游泳运动员的跑长与障碍物大小的比值。我们解析地导出了对稀介质（）有效的阻碍函数的渐近表达式，并利用随机模拟得到了它对致密介质的推广。正如我们所解释的，该模型也很容易推广到描述三维的色散。
Understanding the transport properties of microorganisms and self-propelled particles in porous media has important implications for human health as well as microbial ecology. In free space, most microswimmers perform diffusive random walks as a result of the interplay of self-propulsion and orientation decorrelation mechanisms such as run-and-tumble dynamics or rotational diffusion. In an unstructured porous medium, collisions with the microstructure result in a decrease in the effective spatial diffusivity of the particles from its free-space value. Here, we analyze this problem for a simple model system consisting of noninteracting point particles performing run-and-tumble dynamics through a two-dimensional disordered medium composed of a random distribution of circular obstacles, in the absence of Brownian diffusion or hydrodynamic interactions. The particles are assumed to collide with the obstacles as hard spheres and subsequently slide on the obstacle surface with no frictional resistance while maintaining their orientation, until they either escape or tumble. We show that the variations in the long-time diffusivity can be described by a universal dimensionless hindrance functionof the obstacle area fractionand Péclet number, or ratio of the swimmer run length to the obstacle size. We analytically derive an asymptotic expression for the hindrance function valid for dilute media (), and its extension to denser media is obtained using stochastic simulations. As we explain, the model is also easily generalized to describe dispersion in three dimensions.