Pressure-driven droplet flows through a straight channel are mainly governed by viscous and interfacial forces. The droplet either attains a steady shape, undergoes breakup or fragments into smaller droplets over time. Previous studies have shown that the evolution of droplet depends on various physical parameters including capillary number, viscosity ratio and drop size. In this study, we show that the geometry of the constricted channel also heavily influences the droplet shape, flow properties and onset of different multiphase phenomena. The constriction dimensions, namely length and depth, alter the deformation of droplet and can induce breakup/fragmentation. We also examine the effects of constriction shape on droplet deformation and velocity by defining , a dimensionless quantity based on the relative projected area occupied by the constriction. For multiple constrictions with varying spacing, the phase shift between the upper and lower constrictions promotes enhanced lateral deformation of the droplet. Regime maps based on geometric and physical parameters demonstrate different multiphase regimes and can be helpful in designing constriction geometries suited for various applications.

中文翻译：

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狭窄微通道中的液滴动力学


压力驱动的液滴流过直通道主要受粘性力和界面力控制。随着时间的推移，液滴要么达到稳定的形状，要么破碎或碎裂成更小的液滴。先前的研究表明，液滴的演化取决于各种物理参数，包括毛细管数、粘度比和液滴尺寸。在这项研究中，我们表明收缩通道的几何形状也严重影响液滴形状、流动特性和不同多相现象的发生。收缩尺寸，即长度和深度，会改变液滴的变形，并可能导致破裂/碎裂。我们还通过定义 来检查收缩形状对液滴变形和速度的影响，这是一个基于收缩占据的相对投影面积的无量纲量。对于具有不同间距的多个收缩，上收缩和下收缩之间的相移促进了液滴的横向变形增强。基于几何和物理参数的区域图展示了不同的多相区域，并且有助于设计适合各种应用的收缩几何形状。