Numerical study of satellite droplet formation in dripping faucet

Dynamics of primary and satellite drop formation has wide engineering applications. Drop formation from a vertical capillary tube in air goes through various stages that include necking, bifurcation, recoil, wave gener-ation and secondary necking and bifurcation. In this study, the problem has been studied numerically where the free surface of the pendant drop is tracked by a coupled level set and volume-of-fluid method with the surface tension force determined by the continuum surface force model. The evolution of the complete droplet sepa-ration process has been simulated. The numerical results have been compared with published experimental data. The mechanism for the recoiling of the liquid filament after droplet detachment and the subsequent formation of a satellite droplet has been studied and dynamic correlation among liquid/gas interface topology, velocity and pressure field has been investigated. Bell shaped distribution of axial velocity profile and fast acceleration at the cone-filament junction has been found to lead to satellite drop generation. Parametric studies on the effects of inlet velocity, surface tension coefficient and viscosity have been performed. Satellite droplet is less likely to be formed at high inlet velocity and low surface tension coefficient. Viscosity, on the other hand, has been found to play an important role on the shape of liquid filament and satellite droplet. These findings can help better un-derstanding of drop-on-demand liquid dispensing, inkjet printing, spray combustion and many more engineering applications.

Automated summary

This study numerically analyzed the dynamics of drop formation from a vertical capillary tube, identifying the mechanism of satellite drop formation and liquid filament recoiling after droplet detachment. Parametric studies showed that inlet velocity, surface tension coefficient, and viscosity play important roles in satellite droplet generation.