A front tracking method based multiphase flow simulation (Unverdi and Tryggvason, 1992) is adopted to investigate the transition mechanism of droplet formation modes of dripiing and jetting. The numerical method solves a single set of Navier-Stokes equations for both liquid phases on a fixed Eulerian two-dimensional cylindrical coordinate mesh to account for the fluid flow dynamics. The front tracking method is applied to track the movement of the interface between the two immiscible liquids, and accounts for the surface tension force. This simulation method and computer code have been validated extensively by simulating a single bubble rising in viscous liquid (Hua and Lou, 2006). In this paper, the effects of flow inertial, capillary, viscous, and gravitational forces are all accounted to explore the droplet formation modes and dynamics in the co-flowing system. The preliminary simulation results shown in Fig. 2 indicate that there is sudden jump of droplet size while the sharp transition of droplet formation mode caused by slightly changing outer flow rate. This numerical finding is supported by the experiments (Cramer et al, 2004; Utada et al, 2005). Fig. 3 also shows the droplet formation process under dripping and jetting modes from the initial stage to the steady repeating state of droplet generation. Further studies on the transition mechanism will be elaborated and discussed in the final full paper.
Journal: TechConnect Briefs
Volume: 3, Technical Proceedings of the 2007 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: May 20, 2007
Pages: 452 - 455
Industry sector: Sensors, MEMS, Electronics
Topics: Micro & Bio Fluidics, Lab-on-Chip