Title: Elastic instability of wormlike micelle solution flow in serpentine channels Show Chinese title

Title: 弯曲通道中蠕虫状胶束溶液流动的弹性不稳定现象

Abstract: Wormlike micelle (WLM) solutions are abundant in energy, environmental, and industrial applications, which often rely on their flow through tortuous channels. How does the interplay between fluid rheology and channel geometry influence the flow behavior? Here, we address this question by experimentally visualizing and quantifying the flow of a semi-dilute WLM solution in millifluidic serpentine channels. At low flow rates, the base flow is steady and laminar, with strong asymmetry and wall slip. When the flow rate exceeds a critical threshold, the flow exhibits an elastic instability, producing spatially-heterogeneous, unsteady three-dimensional (3D) flow characterized by two notable features: (i) the formation and persistence of stagnant but strongly-fluctuating and multistable "dead zones" in channel bends, and (ii) intermittent 3D "twists" throughout the bulk flow. The geometry of these dead zones and twisting events can be rationalized by considering the minimization of local streamline curvature to reduce flow-generated elastic stresses. Altogether, our results shed new light into how the interplay between solution rheology and tortuous boundary geometry influences WLM flow behavior, with implications for predicting and controlling WLM flows in a broad range of complex environments. Show Chinese abstract

Abstract: 蠕虫状胶束（WLM）溶液在能源、环境和工业应用中十分丰富，这些应用通常依赖于它们通过曲折通道的流动。 流体力学与通道几何形状之间的相互作用如何影响流动行为？ 在这里，我们通过实验可视化和量化半稀释WLM溶液在毫米级蛇形通道中的流动来回答这个问题。 在低流速下，基流是稳定的且层流的，具有强烈的不对称性和壁滑移现象。 当流速超过某一临界值时，流动表现出弹性不稳定，产生空间异质、非稳态的三维（3D）流动，其特征有两个显著方面：(i) 在通道弯道处形成并持续存在的停滞但强烈波动且多稳态的“死区”，以及(ii) 整个主体流动中的间歇性三维“扭曲”现象。 可以通过考虑最小化局部流线曲率以减少由流动产生的弹性应力来合理解释这些死区和扭曲事件的几何形状。 总而言之，我们的研究结果揭示了溶液流变学与曲折边界几何形状之间相互作用如何影响WLM流动行为的新见解，这对预测和控制复杂环境中广泛的WLM流动具有重要意义。