微流体类伯格斯涡旋中刚性纤维的取向动力学
Orientation Dynamics of Rigid Fibers in a Microfluidic Burgers-like Vortex
中文总结 AI 辅助
该研究结合微流体实验、理论和数值模拟，研究中等雷诺数下流向稳定涡旋中刚性中性浮力纤维的取向动力学，发现其取向由杰弗里方程与伯格斯涡旋模型耦合精确描述，为理解拉伸涡旋流中细长颗粒行为建立了简单框架。
中文摘要 AI 辅助
纤维悬浮液在生物和环境流动中很常见，并广泛应用于工业领域。纤维的传输和取向动力学受与周围流体相互作用的影响，且强烈依赖于流动的性质。现实流动的复杂性，如非均匀或随时间变化，阻碍了对纤维动力学的全面理解。本研究结合微流体实验、理论和数值模拟，研究了在一个可控模型系统——中等雷诺数下的流向稳定涡旋中刚性中性浮力纤维的取向动力学。尽管流动是三维的，但取向动力学非常简单：纤维取向由与伯格斯涡旋模型耦合的杰弗里方程精确描述。我们表明，纤维在流体涡度驱动下绕涡轴进行均匀进动，同时由于涡核中的应变而与涡度对齐。这两种运动是解耦的，对齐时间尺度由局部应变率和纤维长径比决定。有限的颗粒尺寸和惯性会导致与基本流动流线产生微弱偏差，但对取向动力学影响不大。这些结果为理解拉伸涡旋流中细长颗粒的行为建立了一个简单框架，而拉伸涡旋流是湍流的关键组成部分。
英文摘要
Fiber suspensions are common in biological and environmental flows and are widely used in industrial applications. Fiber transport and orientation dynamics are affected by interactions with the surrounding fluid and strongly depend on the nature of the flow. The complexity of realistic flows, which are often heterogeneous or time-dependent, hinders a full understanding of fiber dynamics. In this study, we combine microfluidic experiments, theory and numerical simulations to investigate the orientation dynamics of rigid neutrally buoyant fibers in a well-controlled model system, a streamwise stationary vortex at moderate Reynolds number. Despite the three-dimensional nature of the flow, the orientation dynamics are remarkably simple: the fiber orientation is accurately described by Jeffery equations coupled with the Burgers-vortex model. We show that fibers undergo uniform precession about the vortex axis driven by fluid vorticity while simultaneously aligning with the latter due to strain in the vortex core. These two motions are decoupled, with the alignment timescale determined by the local strain rate and the fiber aspect ratio. Finite particle size and inertia induce weak deviations from the base flow streamlines while leaving the orientational dynamics largely unaffected. These results establish a simple framework for understanding the behavior of elongated particles in stretched vortex flows, which constitute key building blocks of turbulence
