(550g) Smooth Particle Hydrodynamics of Droplet Formation in Microscale Flows

Controlling the formation of droplets and bubbles using microfluidic devices is critical to a range of scientifically-interesting technologies. Presented in this work are simulations of segmented flows involving two immiscible liquids similar to those studied in experimental setups of microchannels. Fully Lagrangian numerical simulations of the multiphase flow are performed using an approach that is a variation of smoothed particle hydrodynamics. At the mesoscopic scale of the flow, the acceleration of fluid particle elements is proportional to local particle density and relative velocity, and those elementary forces tend to drive the system towards local equilibrium. The results at the macroscopic scale show that the relatively simple interactions adequately model the constitutive relations for pressure, viscous, and surface tension forces at the continuum level. The numerical model is applied to investigation of droplet formation in a commonly used T-junction microfluidic laboratory device in order to assess the accuracy of the model in capturing the relative contributions of geometry, fluid viscosity, and interfacial tension. The simulation results are in agreement with experimental observations and analytical droplet size predictions. The model is also shown to be adaptable to a wide range of multiphase and free surface flows.