中国物理B ›› 2024, Vol. 33 ›› Issue (12): 124701-124701.doi: 10.1088/1674-1056/ad84c3

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Flow features induced by a rod-shaped microswimmer and its swimming efficiency: A two-dimensional numerical study

Siwen Li(李斯文)1, Yuxiang Ying(应宇翔)2, Tongxiao Jiang(姜童晓)1, and Deming Nie(聂德明)1,†   

  1. 1 College of Metrology Measurement and Instrument, China Jiliang University, Hangzhou 310018, China;
    2 Institute of Fluid Engineering, Zhejiang University, Hangzhou 310018, China
  • 收稿日期:2024-07-09 修回日期:2024-09-10 接受日期:2024-10-09 发布日期:2024-11-12
  • 通讯作者: Deming Nie E-mail:nieinhz@cjlu.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 12372251 and 12132015) and the Fundamental Research Funds for the Provincial Universities of Zhejiang (Grant No. 2023YW69).

Flow features induced by a rod-shaped microswimmer and its swimming efficiency: A two-dimensional numerical study

Siwen Li(李斯文)1, Yuxiang Ying(应宇翔)2, Tongxiao Jiang(姜童晓)1, and Deming Nie(聂德明)1,†   

  1. 1 College of Metrology Measurement and Instrument, China Jiliang University, Hangzhou 310018, China;
    2 Institute of Fluid Engineering, Zhejiang University, Hangzhou 310018, China
  • Received:2024-07-09 Revised:2024-09-10 Accepted:2024-10-09 Published:2024-11-12
  • Contact: Deming Nie E-mail:nieinhz@cjlu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 12372251 and 12132015) and the Fundamental Research Funds for the Provincial Universities of Zhejiang (Grant No. 2023YW69).

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摘要： The swimming performance of rod-shaped microswimmers in a channel was numerically investigated using the two-dimensional lattice Boltzmann method (LBM). We considered variable-length squirmer rods, assembled from circular squirmer models with self-propulsion mechanisms, and analyzed the effects of the Reynolds number (Re), aspect ratio ($\varepsilon$), squirmer-type factor ($\beta $) and blockage ratio ($\kappa$) on swimming efficiency ($\eta$) and power expenditure ($P$). The results show no significant difference in power expenditure between pushers (microswimmers propelled from the tail) and pullers (microswimmers propelled from the head) at the low Reynolds numbers adopted in this study. However, the swimming efficiency of pushers surpasses that of pullers. Moreover, as the degree of channel blockage increases (i.e., $\kappa $ increases), the squirmer rod consumes more energy while swimming, and its swimming efficiency also increases, which is clearly reflected when $\varepsilon \le 3$. Notably, squirmer rods with a larger aspect ratio $\varepsilon $ and a $\beta $ value approaching 0 can achieve high swimming efficiency with lower power expenditure. The advantages of self-propelled microswimmers are manifested when $\varepsilon > 4$ and $\beta = \pm 1$, where the squirmer rod consumes less energy than a passive rod driven by an external field. These findings underscore the potential for designing more efficient microswimmers by carefully considering the interactions between the microswimmer geometry, propulsion mechanism and fluid dynamic environment.

关键词: direct numerical simulations, low-Reynolds-number motions, multiphase flows, swimming microorganisms

Abstract: The swimming performance of rod-shaped microswimmers in a channel was numerically investigated using the two-dimensional lattice Boltzmann method (LBM). We considered variable-length squirmer rods, assembled from circular squirmer models with self-propulsion mechanisms, and analyzed the effects of the Reynolds number (Re), aspect ratio ($\varepsilon$), squirmer-type factor ($\beta $) and blockage ratio ($\kappa$) on swimming efficiency ($\eta$) and power expenditure ($P$). The results show no significant difference in power expenditure between pushers (microswimmers propelled from the tail) and pullers (microswimmers propelled from the head) at the low Reynolds numbers adopted in this study. However, the swimming efficiency of pushers surpasses that of pullers. Moreover, as the degree of channel blockage increases (i.e., $\kappa $ increases), the squirmer rod consumes more energy while swimming, and its swimming efficiency also increases, which is clearly reflected when $\varepsilon \le 3$. Notably, squirmer rods with a larger aspect ratio $\varepsilon $ and a $\beta $ value approaching 0 can achieve high swimming efficiency with lower power expenditure. The advantages of self-propelled microswimmers are manifested when $\varepsilon > 4$ and $\beta = \pm 1$, where the squirmer rod consumes less energy than a passive rod driven by an external field. These findings underscore the potential for designing more efficient microswimmers by carefully considering the interactions between the microswimmer geometry, propulsion mechanism and fluid dynamic environment.

Key words: direct numerical simulations, low-Reynolds-number motions, multiphase flows, swimming microorganisms

中图分类号:  (Direct numerical simulations)

  • 47.27.ek
47.63.mf (Low-Reynolds-number motions) 47.61.Jd (Multiphase flows) 47.63.Gd (Swimming microorganisms)