A local approximation model for macroscale transport of biased active Brownian particles in a flowing suspension
A local approximation model for macroscale transport of biased active Brownian particles in a flowing suspension
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DOI：
10.1017/jfm.2022.10
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发表时间：
2022-01-31
影响因子：
3.7
通讯作者：
Hwang, Yongyun
中科院分区：
文献类型：
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作者：
Fung, Lloyd;Bearon, Rachel N.;Hwang, Yongyun
运动微生物的稀悬浮液受到强烈的环境流，如海洋中的藻类，可以建模为一个人口的非相互作用，定向的活性布朗粒子（ABPs）。利用Smoluchowski方程（即空间和方向上的Fokker-Planck方程），可以描述ABPs的非平凡输运现象，如趋性和剪切诱导迁移。这项工作将Smoluchowski方程转化为输运方程，其中漂移和弥散可以进一步近似为局部流场的函数。新模型可以应用于任何全球流场，由于其局部性质，不像以前的方法，如利用广义泰勒色散理论。转换表明，整体漂移包括有偏向的运动的个别粒子的存在下的的士和剪切诱导的迁移的士的情况下。此外，它还揭示了由ABP的定向动力学与被动平流扩散之间的相互作用引起的其他新的漂移和分散。最后，该模型的性能进行评估，使用的例子回旋悬浮液，该模型被证明是最准确的偏置运动的颗粒（即的士）是弱的。
A dilute suspension of motile microorganisms subjected to a strong ambient flow, such as algae in the ocean, can be modelled as a population of non-interacting, orientable active Brownian particles (ABPs). Using the Smoluchowski equation (i.e. Fokker-Planck equation in space and orientation), one can describe the non-trivial transport phenomena of ABPs such as taxis and shear-induced migration. This work transforms the Smoluchowski equation into a transport equation, in which the drifts and dispersions can be further approximated as a function of the local flow field. The new model can be applied to any global flow field due to its local nature, unlike previous methods such as those utilising the generalised Taylor dispersion theory. The transformation shows that the overall drift includes both the biased motility of individual particles in the presence of taxis and the shear-induced migration in the absence of taxis. In addition, it uncovers other new drifts and dispersions caused by the interactions between the orientational dynamics and the passive advection-diffusion of ABPs. Finally, the performance of this model is assessed using examples of gyrotactic suspensions, where the proposed model is demonstrated to be most accurate when the biased motility of particles (i.e. taxis) is weak.