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Drop Formation from a Wettable Nozzle

The process of drop formation from a nozzle can be seen in many natural systems and engineering applications. Here, we investigate the formation of a liquid droplet from a wettable nozzle. The behavior of a drop is complicated due to an interplay among gravity, capillary rise, viscous drag, and surface tension. In experiments, we observe that drops forming from a wettable nozzle initially climb the outer walls of the nozzle due to surface tension. Then, when the weightof the drops gradually increases, they finally fall due to gravity. By changing the parameters like the nozzle size and fluid flow rate, we have observed that different behaviors of the droplets. Such oscillatory behavior is characterized by a nonlinear equation that consists of capillary rise, viscous drag, and gravity. Two asymptotic solutions in the initial and later stages of drop formation are obtained and show good agreement with experimental observations.