Deformation and breakup of a droplet in media with density contrasts: A numerical study using the color-gradient lattice Boltzmann method

We investigate the deformation and breakup behavior of a single droplet in shear and extensional flows, focusing on the effects of the density contrast between the droplet (dispersed phase) and the surrounding matrix fluid (continuous phase). Although many studies have explored the droplet dynamics in such flows, the influence of the density ratio is not yet fully understood. To address this gap, we employ the color-gradient lattice Boltzmann method and perform numerical analysis across a wide range of density ratios and capillary numbers in the Stokes flow regime. We quantify the droplet deformation, elucidate the effects of the density ratio, and carefully analyze the breakup modes, including tip streaming breakup. We confirm that the tip streaming breakup occurs only when the density contrast is large, with values ranging from approximately 1:100 to 1:300 within the test limits. Finally, the flow fields within the droplet are analyzed to elucidate the hydrodynamic origins of these distinct breakup modes.