Phase segregation of a partially miscible binary mixture subjected to an external force field

• Published in: Journal of fluid mechanics Vol. 997
• Main Authors: Chueh, Chih-Che, Mauri, Roberto, Bertei, Antonio
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 10.10.2024
• Subjects: JFM Papers; suspensions; breakup/coalescence; Marangoni convection
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/jfm.2024.841

When a partially miscible binary mixture is quenched below its critical temperature, it transitions from its single-phase to a two-phase region, undergoing phase separation. The processes of formation and coalescence of droplets are driven by diffusive and convective phenomena, taking place isotropically in the system. The application of an external force field, which exerts a different contribution on the two species, breaks the symmetry of phase separation, leading to the segregation of two equilibrated phases separated by a single interface. This study investigates the dynamics of phase segregation under an external force. The effects of various force magnitudes, captured by the Bond number, in both high- and low-viscosity mixtures, distinguished by different fluidity numbers, are quantified via numerical simulations by using the phase field model. The intricate dynamics of formation, floating and coalescence of droplets towards complete segregation are described along with the quantification of the segregation time, revealing different patterns for high and low Bond numbers. Results show that in none of the cases, formation and floating can be regarded as strictly serial processes. A universal scaling between segregation time, Bond number, fluidity number and domain size is not possible, with a power-law dependence emerging only under the diffusion-dominated regime.