Barrett Aaron, Fogelson Aaron L, Gregory Forest M, Gruninger Cole, Lim Sookkyung, Griffith Boyce E
Department of Mathematics, University of Utah, Salt Lake City, UT, USA.
Departments of Mathematics and Biomedical Engineering, University of Utah, Salt Lake City, UT, USA.
J Fluid Mech. 2024 Nov 25;999. doi: 10.1017/jfm.2024.666. Epub 2024 Nov 11.
Microorganism motility often takes place within complex, viscoelastic fluid environments, e.g., sperm in cervicovaginal mucus and bacteria in biofilms. In such complex fluids, strains and stresses generated by the microorganism are stored and relax across a spectrum of length and time scales and the complex fluid can be driven out of its linear response regime. Phenomena not possible in viscous media thereby arise from feedback between the swimmer and the complex fluid, making swimming efficiency co-dependent on the propulsion mechanism and fluid properties. Here we parameterize a flagellar motor and filament properties together with elastic relaxation and nonlinear shear-thinning properties of the fluid in a computational immersed boundary model. We then explore swimming efficiency, defined as a particular flow rate divided by the torque required to spin the motor, over this parameter space. Our findings indicate that motor efficiency (measured by the volumetric flow rate) can be boosted or degraded by relatively moderate or strong shear-thinning of the viscoelastic environment.
微生物的运动通常发生在复杂的粘弹性流体环境中，例如，宫颈阴道粘液中的精子和生物膜中的细菌。在这种复杂流体中，微生物产生的应变和应力会在一系列长度和时间尺度上存储和松弛，并且复杂流体可能会偏离其线性响应范围。粘性介质中不可能出现的现象因此源于游动者与复杂流体之间的反馈，使得游泳效率共同依赖于推进机制和流体特性。在这里，我们在计算浸入边界模型中，将鞭毛马达和细丝特性与流体的弹性松弛和非线性剪切变稀特性一起进行参数化。然后，我们在这个参数空间中探索游泳效率，将其定义为特定流速除以驱动马达所需的扭矩。我们的研究结果表明，粘弹性环境相对适度或强烈的剪切变稀可以提高或降低马达效率（通过体积流速来衡量）。
