Effect of magnetic field on motion, deformation and separation time of Newtonian and non-Newtonian fluid droplets in a flow‐focusing microchannel

In the present study, the effect of external magnetic field on the process of droplet formation with different size and frequency in a flow-focusing micro-channel is numerically studied. Moreover, the influence of non-Newtonian properties on the droplet formation characteristics is investigated using two non-Newtonian Carreau and power-law models. In order to solve the continuity and momentum equations for unsteady, two-phase and incompressible flow, finite volume method is employed. A numerical algorithm based on volume of fluid (VOF) technique is used to determine the effect of Bond number (0 to 0.2) and power-law indices (0.3, 0.6 and 1.3) on the droplet formation process along with their size and separation time. In order to validate the numerical solution, the formation of Newtonian fluid droplets at different values of magnetic field strength is compared with the results of other studies and very good agreement was observed. The results of numerical solution show that Carreau fluid droplet in the Bond number of 0.2 has the highest volume, which is equivalent to the dimensionless volume of 1.56. Also, the process of droplet formation is more affected by the magnetic field than by the non-Newtonian model. In addition, with increasing field strength, droplet separation time increases and as a result, larger droplets with lower frequency will be formed.