Hydrodynamic interaction of two swimming model micro-organisms
Hydrodynamic interaction of two swimming model micro-organisms
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DOI：
10.1017/s0022112006002631
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发表时间：
2006-12-10
影响因子：
3.7
通讯作者：
Pedley, T. J.
中科院分区：
文献类型：
--
作者：
Ishikawa, Takuji;Simmonds, M. P.;Pedley, T. J.
为了了解游动微生物悬浮液的流变学和运输特性，有必要分析成对游动细胞的流体动力学相互作用。在本文中，游泳的微生物被建模为具有规定切向表面速度的蠕动球体，称为蠕动体。球体的质心可能会偏离几何中心（底重）。惯性和布朗运动的影响被忽略，因为真正的微生物在非常低的雷诺数下游泳，但对于布朗效应来说太大了而不重要。两个蠕动器的相互作用是针对小分离和大分离的极限进行分析计算的，并且还使用边界元方法进行数值计算。两个蠕动器的平移旋转速度和应力波的分析结果和数值结果非常吻合。我们试图为一对相互作用的蠕动者生成一个数据库，从中可以轻松预测一组蠕动者的运动。两个相互作用的蠕动者的行为也从现象学角度进行了讨论。两个蠕动体的轨迹结果表明，首先蠕动体相互吸引，然后当它们靠近时它们会急剧改变方向，最后它们彼此分离。底部沉重的影响是相当大的。将轨迹限制为二维会产生误导性结果。该论文的在线版本提供了一些蠕动互动的电影。
In order to understand the rheological and transport properties of a suspension of swimming micro-organisms, it is necessary to analyse the fluid-dynamical interaction of pairs of such swimming cells. In this paper, a swimming micro-organism is modelled as a squirming sphere with prescribed tangential surface velocity, referred to as a squirmer. The centre of mass of the sphere may be displaced from the geometric centre (bottom-heaviness). The effects of inertia and Brownian motion are neglected, because real micro-organisms swim at very low Reynolds numbers but are too large for Brownian effects to be important. The interaction of two squirmers is calculated analytically for the limits of small and large separations and is also calculated numerically using a boundary-element method. The analytical and the numerical results for the translational-rotational velocities and for the stresslet of two squirmers correspond very well. We sought to generate a database for an interacting pair of squirmers from which one can easily predict the motion of a collection of squirmers. The behaviour of two interacting squirmers is discussed phenomenologically, too. The results for the trajectories of two squirmers show that first the squirmers attract each other, then they change their orientation dramatically when they are in near contact and finally they separate from each other. The effect of bottom-heaviness is considerable. Restricting the trajectories to two dimensions is shown to give misleading results. Some movies of interacting squirmers are available with the online version of the paper.