Numerical simulation of droplet formation in different microfluidic devices

This study aims to assess the droplet formation process in microfluidic devices using an all Mach-number multi-phase flow solver. Harten-Lax-van Leer-Contact (HLLC) Riemann solver is implemented for solving the discretized equations while Tangent of Hyperbola for INterface Capturing (THINC) method is applied to reduce the excessive diffusion of the method at the interface. The multi-block strategy is implemented in the flow solver to improve its capability of simulating flows in more complicated, multi-port droplet formation geometries. First, the computational performance of the numerical solver is validated through simulating the benchmark Rayleigh-Taylor instability problem and the droplet formation in a planar flow-focusing geometry. The comparison of numerical results with available analytical/experimental data indicates a precise prediction of flow features. Then, the droplet generation process in coflowing devices with Newtonian liquid is numerically studied. Finally, the shear-thinning effects of the dispersed and continuous phase on the drop formation characteristics are investigated. It is shown that deviation of the continuous phase from Newtonian behavior has a strong impact on droplet size, speed, and generation rate. On the other hand, assuming the dispersed phase as non-Newtonian does not strongly affect the aforementioned properties of the droplet formation regime.