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

• Published in: Chinese physics B Vol. 33; no. 12; pp. 124701 - 355
• Main Authors: Li, Siwen, Ying, Yuxiang, Jiang, Tongxiao, Nie, Deming
• Format: Journal Article
• Language: English
• Published: Chinese Physical Society and IOP Publishing Ltd 01.11.2024
• Subjects: direct numerical simulations; low-Reynolds-number motions; multiphase flows; swimming microorganisms; direct numerical simulations; low-Reynolds-number motions; multiphase flows; swimming mi-croorganisms
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/ad84c3

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 ( ε ), squirmer-type factor ( β ) and blockage ratio ( κ ) on swimming efficiency ( η ) 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., κ increases), the squirmer rod consumes more energy while swimming, and its swimming efficiency also increases, which is clearly reflected when ε ≤ 3. Notably, squirmer rods with a larger aspect ratio ε and a β value approaching 0 can achieve high swimming efficiency with lower power expenditure. The advantages of self-propelled microswimmers are manifested when ε > 4 and β = ±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.