Research on sedimentation characteristics of squirmer in a power-law fluid

IF 1.8 4区物理与天体物理 Q4 CHEMISTRY, PHYSICAL

The European Physical Journal E Pub Date : 2024-10-15 DOI:10.1140/epje/s10189-024-00457-0

Amin Ullah, Jianzhong Lin, Yuxiang Yin

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Abstract

Sedimentation characteristics of a squirmer in a power-law fluid within a vertical channel are studied numerically using the two-dimensional lattice Boltzmann method. The effects of swimming type (− 5 ≤ β ≤ 5), self-propelling strength (0.5 ≤ α ≤ 1.1), power-law indexes (0.5 ≤ n ≤ 1.5), and the density ratio of the squirmer to the fluid (γ = 1.01, 1.5 and 2.3) on the sedimentation of the squirmer are analyzed. Four settlement patterns are identified: steady falling in the center, downward along the wall, oscillating with large amplitude and oscillating around the centerline. The squirmer in the channel exhibits more fluctuations in shear-thinning (n < 1) and Newtonian (n = 1) fluids compared to shear-thickening fluids (n > 1). Additionally, a puller (β > 0) settles faster than a pusher (β < 0) in shear-thinning and Newtonian fluids. Puller generates flow towards their head and away from their tail, exhibiting small amplitude oscillations. Pushers exhibit higher amplitude oscillations throughout the channel, creating flow towards their tail and away from their head. At lower γ, the fluctuation of the squirmer is less pronounced compared to higher γ.

Graphical abstract

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幂律流体中蜗杆的沉降特性研究

采用二维晶格玻尔兹曼方法对垂直通道内幂律流体中的蜗牛沉积特性进行了数值研究。分析了游动类型（- 5 ≤ β ≤ 5）、自推进强度（0.5 ≤ α ≤ 1.1）、幂律指数（0.5 ≤ n ≤ 1.5）和松鼠与流体的密度比（γ = 1.01、1.5 和 2.3）对松鼠沉降的影响。确定了四种沉降模式：中心稳定下降、沿壁向下沉降、大振幅振荡和绕中心线振荡。与剪切增稠流体（n >1）相比，在剪切稀化流体（n <1）和牛顿流体（n = 1）中，水槽中的唧筒表现出更大的波动。此外，在剪切稀化流体和牛顿流体中，牵引器（β >0）的沉降速度快于推流器（β <0）。拉力器产生流向头部和远离尾部的流动，表现出小振幅振荡。推流器在整个通道中表现出较高的振幅振荡，产生流向尾部和远离头部的流动。γ值较低时，推流器的波动没有γ值较高时明显。

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来源期刊

The European Physical Journal E CHEMISTRY, PHYSICAL-MATERIALS SCIENCE, MULTIDISCIPLINARY

CiteScore

2.60

自引率

5.60%

发文量

审稿时长

3 months

期刊介绍： EPJ E publishes papers describing advances in the understanding of physical aspects of Soft, Liquid and Living Systems. Soft matter is a generic term for a large group of condensed, often heterogeneous systems -- often also called complex fluids -- that display a large response to weak external perturbations and that possess properties governed by slow internal dynamics. Flowing matter refers to all systems that can actually flow, from simple to multiphase liquids, from foams to granular matter. Living matter concerns the new physics that emerges from novel insights into the properties and behaviours of living systems. Furthermore, it aims at developing new concepts and quantitative approaches for the study of biological phenomena. Approaches from soft matter physics and statistical physics play a key role in this research. The journal includes reports of experimental, computational and theoretical studies and appeals to the broad interdisciplinary communities including physics, chemistry, biology, mathematics and materials science.