Onset of Coalescence in Two-Phase System.

This video presents a high-resolution Finite Element Method (FEM) simulation of a two-phase flow system at the onset of coalescence, highlighting the oscillatory interaction that develops as the interfaces approach each other before merging. The color field represents the magnitude of the vertical velocity, where red indicates high velocity regions and blue indicates low velocity regions, revealing the complex coupling between inertia, viscosity, and surface tension in a surface-tension-dominated regime. The simulation was performed with time step dt = 0.02 over 10,000 iterations, using the following parameters: D = 2.17, g = 0.0, sigma = 4.59, mu_in = 0.5, mu_out = 1.0, rho_in = 0.01, rho_out = 1.0, Morton number Mo = 1e-6, Eotvos number Eo = 10, Reynolds number Re = sqrt(N), Weber number We = 10, and Froude number Fr = 1. This computation demonstrates the ability of FEM to accurately resolve interfacial deformation and transient dynamics in complex two-phase systems.