A note on a swirling squirmer in a shear-thinning fluid
A note on a swirling squirmer in a shear-thinning fluid
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DOI：
10.1063/5.0029068
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发表时间：
2020-11
影响因子：
4.6
通讯作者：
H. Nganguia;K. Zheng;Y. Chen;O. S. Pak;Lailai Zhu
中科院分区：
文献类型：
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作者：
H. Nganguia;K. Zheng;Y. Chen;O. S. Pak;Lailai Zhu
微生物和人工微晶状体通常会在表现出复杂的流变行为的生物流体中移动，包括粘弹性和剪切粘稠的粘度。对各种类型的复杂液体中不同游泳步态的有效性的全面理解仍然难以捉摸。蠕虫模型通常用于表示不同类型的游泳者，并探究了不同类型的复杂流变学对运动的影响。尽管许多研究仅集中在极性方向上表面速度的蠕动者，但最近的一项研究表明，旋转运动的蠕动器可以在粘弹性流体中比在牛顿液中更快地游泳[Binagia等人[Binagia et al。，J。Fluid Mech。 900，A4，（2020）]。在这里，我们考虑了类似的设置，但由于剪切粘稠的粘度而着重于唯一效果。我们使用渐近分析和数值模拟来检查旋流流程如何在剪切薄薄的但无弹性的流体中影响Carreau构成方程所描述的蠕虫的游泳性能。我们的结果表明，旋流流可以根据carreau数量增加或降低蠕虫的速度。与在粘弹性流体中游泳相反，在剪切稀释的流体中旋转蠕动的速度不会超出牛顿的价值，而在广泛的参数中。我们还阐明了方位角与剪切粘度的耦合如何产生旋转推动器或拉杆的旋转运动。
Micro-organisms and artificial microswimmers often move in biological fluids displaying complex rheological behaviors, including viscoelasticity and shear-thinning viscosity. A comprehensive understanding of the effectiveness of different swimming gaits in various types of complex fluids remains elusive. The squirmer model has been commonly used to represent different types of swimmers and probe the effects of different types of complex rheology on locomotion. While many studies focused only on squirmers with surface velocities in the polar direction, a recent study has revealed that a squirmer with swirling motion can swim faster in a viscoelastic fluid than in Newtonian fluids [Binagia et al., J. Fluid Mech. 900, A4, (2020)]. Here, we consider a similar setup but focus on the sole effect due to shear-thinning viscosity. We use asymptotic analysis and numerical simulations to examine how the swirling flow affects the swimming performance of a squirmer in a shear-thinning but inelastic fluid described by the Carreau constitutive equation. Our results show that the swirling flow can either increase or decrease the speed of the squirmer depending on the Carreau number. In contrast to swimming in a viscoelastic fluid, the speed of a swirling squirmer in a shear-thinning fluid does not go beyond the Newtonian value in a wide range of parameters considered. We also elucidate how the coupling of the azimuthal flow with shear-thinning viscosity can produce the rotational motion of a swirling pusher or puller.