Sara Tomasi Masoni, Alessandro Mariotti, Chiara Galletti, Roberto Mauri, Maria Vittoria Salvetti, Elisabetta Brunazzi
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引用次数: 0
摘要
实验和模拟相结合,全面了解了在流体动力流聚焦配置下运行的 X 微装置中产生藻酸盐液滴的捏合机制。在 X 微装置的一个入口通道中注入海藻酸水溶液,而在另外两个入口通道中注入葵花籽油和斯盘80。使用自适应网格细化和流体体积法可以在数值模拟中准确跟踪界面。通过专门的模拟集估算了数值预测对接触角和表面张力的敏感性。随后,对不同流速下的数值模拟和实验进行了比较,结果令人满意。我们观察到,除主液滴外,捏合机制还可能导致形成多个卫星液滴。根据主液滴中包裹的海藻酸数量,我们提出了一种捏合性能指标。讨论了操作条件对捏合效率、频率和液滴直径的影响,为优化液滴生产提供了有价值的信息。捏合效率与液体螺纹的长度和直径密切相关。在低流速下,观察到的液体螺纹较短。这导致形成的卫星数量少,因此捏合效率高,但液滴产量低。提高分散相流速会略微降低效率,但会显著提高产量。
Formation of sodium-alginate droplets in an X-microdevice: Characterization of the pinching efficiency
Experiments and simulations are used jointly to gain a comprehensive insight into the pinching mechanism that generates alginate droplets in an X-microdevice operating in a hydrodynamic flow-focusing configuration. The X-microdevice is fed with an aqueous alginate solution into one inlet channel, while sunflower oil and Span80 are fed into the other two inlet channels. The use of the adaptive mesh refinement and volume of fluid method allows accurate tracking of the interface in numerical simulations. The sensitivities of numerical predictions to the contact angle and the surface tension are estimated through dedicated sets of simulations. Subsequently, numerical simulations and experiments are compared for different flow rates with a satisfactory agreement. We observe that the pinch-off mechanism may lead to the formation of several satellite drops in addition to the main droplet. A pinching performance indicator is suggested based on the amount of alginate that is encapsulated in the main droplet. The effect of operating conditions on the pinching efficiency, frequency, and droplet diameter is discussed to provide valuable information to optimize the droplets production. The pinching efficiency is closely related to the length and diameter of the liquid thread. At low flow rates, a short liquid thread is observed. This leads to the formation of few satellites and, thus, to high pinching efficiency but low droplet production. Increasing the dispersed-phase flow rate slightly reduces the efficiency but significantly increases the production.
期刊介绍:
Physics of Fluids (PoF) is a preeminent journal devoted to publishing original theoretical, computational, and experimental contributions to the understanding of the dynamics of gases, liquids, and complex or multiphase fluids. Topics published in PoF are diverse and reflect the most important subjects in fluid dynamics, including, but not limited to:
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