Benchmark numerical simulations of segmented two-phase flows in microchannels using the Volume of Fluid method

We present an extensive analysis of the performance of the Volume of Fluid (VOF) method, as implemented in OpenFOAM, in modeling the flow of confined bubbles and droplets (“segmented flows”) in microfluidics. A criterion for having a sufficient grid solution to capture the thin lubricating film surrounding non-wetting bubbles or droplets, and the precise moment of breakup or coalescence is provided. We analyze and propose optimal computational settings to obtain a sharp fluid interface and small parasitic currents. To show the usability of our computational rules, numerical simulations are presented for three benchmark cases, viz. the steady motion of bubbles in a straight two-dimensional channel, the formation of bubbles in two- and three-dimensional T-junctions, and the breakup of droplets in three-dimensional T-junctions. An error analysis on the accuracy of the computations is presented to probe the efficacy of the VOF method. The results are in good agreement with published experimental data and experimentally-validated analytical solutions.