槽道各向异性黏弹性流体中微生物游动特性的数值研究
NUMERICAL STUDY OF THE MICROORGANISMS SWIMMING IN ANISOTROPIC VISCOELASTIC FLUIDS IN CHANNEL
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摘要: 近年来, 微生物游动特性的研究逐渐成为流体力学的热点问题之一. 深入了解微生物在复杂流体中的游动特性可以为微型器件的设计制造提供帮助. 已有研究结果表明, 管道中微生物存在复杂的行为特征, 其内在的动力学机理尚未清楚. 本文采用浸没边界法, 引入泰勒波动板模型, 探讨槽道中微生物在各向异性黏弹性流体中的游动特性; 重点分析槽道壁面约束对微生物行为特征的影响规律. 数值模拟结果表明, 与自由游动相比, 槽道中微生物游动呈现加速现象, 而且槽道壁面附近加速效果更显著. 另外, 槽道中微生物游动效率比自由游动时更高. 进一步受力分析, 发现流体压力对微生物游动起推动作用, 黏性力起阻碍作用. 与这两者相比, 聚合物产生的弹性力则小很多, 几乎可以忽略. 槽道中微生物受到更大的流体压力, 认为加速现象与此相关.Abstract: Recently, microorganisms swimming in channel has gradually become one of the hot issues. The deep understanding of the microorganism swimming in complex fluids can provide guidance for the design and manufacture of micro-devices. There are complex behaviors when microorganisms swimming in channel and the hydrodynamic mechanism has not yet been clarified. In our work, immersed boundary method is adopted, and the Taylor’s swimming sheet model is introduced to investigate the swimming characteristics of micro-swimmer in anisotropic viscoelastic fluid in the channel. We focus on analyzing the effects of the wall on the micro-swimmer behaviors. Our results show that the micro-swimmer speeds up in channel, and it is significant when micro-swimmer close to the channel wall. In addition, the swimming efficiency in channel is greater than that of free swimming. We obverse that pressure plays a role in promoting the swimming of microorganisms and viscous force acts as a hindrance. Elastic force produced by the polymer is much smaller. The micro-swimmer gains greater pressure when swimming in channel, and we believe it is related to the acceleration phenomenon of microswimmer.