This work studies the spontaneous droplet flow in tubes with different wettability gradient and number of segments by using a particle-based numerical method, many-body dissipative particle dynamics (MDPD). The study aims to understand how the different contact angle sets (gradient contact angle distribution along with different segments of a tube) and the number of segments could affect the droplet flow velocity and time to reaching a stable state. Simulation results show that even with the same wettability gap, a contact angle set with higher values of contact angle along the tube segments can drive the droplet to flow faster in the tubes; moreover, with the same contact angle set and tube length, the tubes with fewer segments can allow a faster flow of droplet, thus a shorter time to reaching the stable state. The numerical findings in this work can provide a new idea and direction for the design of droplet-based microfluidic systems.

中文翻译：

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管中液滴的自发运动：表面润湿性和片段长度的影响

这项工作通过使用基于粒子的数值方法，多体耗散粒子动力学（MDPD）研究具有不同润湿性梯度和段数的管中的自发液滴流动。该研究旨在了解不同的接触角组（梯度接触角分布以及管的不同段）和段数如何影响液滴流速和达到稳定状态的时间。仿真结果表明，即使润湿性间隙相同，沿管段设置较高接触角的接触角可以驱动液滴在管中流动得更快；此外，在相同的接触角设置和管长的情况下，管段较少的管子可以让液滴更快地流动，从而达到稳定状态的时间更短。