A quantitative comparison of physical accuracy and numerical stability of Lattice Boltzmann color gradient and pseudopotential multicomponent models for the jetting of microdroplets

The performances of the Color-Gradient (CG) and of the Shan-Chen (SC) multicomponent Lattice Boltzmann models are quantitatively compared side-by-side on multiple physical flow problems where breakup, coalescence and contraction of fluid ligaments are important. These include flow problems relevant to microfluidic applications, such as the jetting of microdroplets as seen in inkjet printing. Specifically we consider droplet oscillation, ligament contraction and Rayleigh-Plateau instability simulations. One to one comparisons between CG and SC are made to compare their performance. Our results show that the CG model is a suitable choice for challenging simulations of droplet formation, due to numerical stability, physical accuracy and wide range of accessible parameters. A realistic jetting simulation with typical fluid parameters found in industrial applications is shown to be achievable using the Color-Gradient model. Specifically, the jetting simulation features tunable nozzle wetting boundary conditions and a high ink-air density ratio of 1000 at a capillary number, Ca = 1.61, determined by the surface tension, viscosity and jetting velocity of the ink.