Bonacci Francesco, Chakrabarti Brato, Saintillan David, du Roure Olivia, Lindner Anke
PMMH, CNRS, ESPCI Paris, Université PSL, Sorbonne Université, Université Paris Cité, F-75005, Paris, France.
Center for Computational Biology, Flatiron Institute, New York, New York 10010, USA.
J Fluid Mech. 2023 Jan 19;955. doi: 10.1017/jfm.2022.1040. eCollection 2023 Jan 25.
The fluid-structure interactions between flexible fibers and viscous flows play an essential role in various biological phenomena, medical problems, and industrial processes. Of particular interest is the case of particles freely transported in time-dependent flows. This work elucidates the dynamics and morphologies of actin filaments under oscillatory shear flows by combining microfluidic experiments, numerical simulations, and theoretical modeling. Our work reveals that, in contrast to steady shear flows, in which small orientational fluctuations from a flow-aligned state initiate tumbling and deformations, the periodic flow reversal allows the filament to explore many different configurations at the beginning of each cycle. Investigation of filament motion during half time periods of oscillation highlights the critical role of the initial filament orientation on the emergent dynamics. This strong coupling between orientation and deformation results in new deformation regimes and novel higher-order buckling modes absent in steady shear flows. The primary outcome of our analysis is the possibility of suppression of buckling instabilities for certain combinations of the oscillation frequency and initial filament orientation, even in very strong flows. We explain this unusual behavior through a weakly nonlinear Landau theory of buckling, in which we treat the filaments as inextensible Brownian Euler-Bernoulli rods whose hydrodynamics are described by local slender-body theory.
柔性纤维与粘性流之间的流固相互作用在各种生物现象、医学问题和工业过程中起着至关重要的作用。特别值得关注的是颗粒在随时间变化的流中自由传输的情况。这项工作通过结合微流体实验、数值模拟和理论建模，阐明了振荡剪切流下肌动蛋白丝的动力学和形态。我们的工作表明，与稳定剪切流不同，在稳定剪切流中，从与流对齐状态产生的小取向波动会引发翻滚和变形，而周期性的流反转使细丝在每个周期开始时能够探索许多不同的构型。对振荡半周期内细丝运动的研究突出了初始细丝取向对出现的动力学的关键作用。这种取向与变形之间的强耦合导致了稳定剪切流中不存在的新变形模式和新型高阶屈曲模式。我们分析的主要结果是，即使在非常强的流中，对于振荡频率和初始细丝取向的某些组合，也有可能抑制屈曲不稳定性。我们通过屈曲的弱非线性朗道理论来解释这种不寻常的行为，在该理论中，我们将细丝视为不可伸长的布朗欧拉 - 伯努利杆，其流体动力学由局部细长体理论描述。
