弹性尾迹介导并排悬臂阵列中的集体粘弹性流固相互作用
Elastic wakes mediate collective viscoelastic fluid-structure interactions in side-by-side cantilever arrays
AI总结：
该研究探究并排悬臂阵列的粘弹性流固相互作用，发现弹性尾迹合并等集体行为依赖流体剪切稀化特性与阵列构型，揭示了集体不稳定性的形成机制。
AI中文摘要：
低雷诺数下粘弹性流体流过可变形结构时的流固相互作用（FSI）仍知之甚少，尽管其与纤毛、鞭毛等生物系统以及工程微系统密切相关。我们采用自下而上的方法研究并排柔性悬臂阵列中的粘弹性流固相互作用，系统改变悬臂数量和测试流体的流变特性，对比弱剪切稀化（WS）和强剪切稀化（HS）的聚氧乙烯溶液。对于两种流体，随着魏森贝格数（Wi）增大，单个孤立悬臂后方会形成拉长的弹性尾迹。对于多个悬臂，WS流体在临界魏森贝格数（Wi*）处发生从分离到合并弹性尾迹的转变，伴随发散流场的出现和悬臂向展向的协同向内偏转；当阵列中悬臂数量从2增加到3时，临界Wi*增大，表明转变的起始对阵列构型有强烈依赖。对于HS流体，尽管弹性相当且形成了弹性尾迹，但在研究的全部Wi范围内，尾迹合并、流场发散和悬臂向内偏转均被抑制。这种对比表明，仅弹性会促进尾迹形成，但不足以产生集体不稳定性，集体不稳定性还需要剪切稀化和相邻悬臂间的相互作用。这些发现表明，柔性阵列中的粘弹性流固相互作用由流体弹性、剪切稀化和几何构型的综合效应控制，弹性尾迹相互作用介导了集体不稳定性，并将局部弹性尾迹与阵列尺度的结构响应关联起来。
英文摘要：
Fluid-structure interaction (FSI) in viscoelastic flows past deformable structures at low Reynolds numbers remains poorly understood, despite its relevance to biological systems such as cilia and flagella, and to engineered microsystems. We investigate viscoelastic FSI in side-by-side flexible cantilever arrays using a bottom-up approach that systematically varies the number of cantilevers and the rheology of the test fluid, comparing weakly shear-thinning (WS) and highly shear-thinning (HS) polyethylene oxide solutions. For both fluids, with increasing Weissenberg number (Wi), an elongated elastic wake develops behind a single isolated cantilever. For multiple cantilevers, the WS fluid undergoes a transition at a critical Weissenberg number (Wi*) from separated to merged elastic wakes, accompanied by the emergence of a divergent flow field and coordinated inward spanwise cantilever deflection. The critical Wi* increases as the number of cantilevers in the array is increased from two to three, demonstrating a strong dependence of the onset on the array configuration. For the HS fluid, wake merger, flow divergence, and inward cantilever deflection are suppressed across the full range of Wi investigated, despite comparable elasticity and the formation of elastic wakes. This contrast shows that elasticity alone promotes wake formation but is insufficient to produce the collective instability, which instead requires both shear-thinning and interactions between neighboring cantilevers. These findings demonstrate that viscoelastic FSI in flexible arrays is governed by the combined effects of fluid elasticity, shear-thinning, and geometric configuration, with elastic wake interactions mediating the collective instability and linking local elastic wakes to array-scale structural response.
