| Oscillation, coalescence, and collision of drops are studied numerically using a Finite-Difference/Front-Tracking Method to solve the full Navier-Stokes equations. Several problems are solved. Simulations of oscillations are analyzed to check the accuracy. The results obtained for linear oscillation of a viscous drop immersed in a host-fluid are in very good agreement with the available theory.;The coalescence of two initially stationary drops of different size due to surface tension energy results in two distinct evolutions depending on the droplet viscosity. The first case, when the viscosity is low, involves a large mixing in which the small drop penetrates far into the large one and forms a vortex ring. The second case occurs when the viscosity is high. Here, because of high dissipation the penetration depth is low, and there is no appreciable mixing. The dependency of the penetration depth on the size ratio of the drops and the non-dimensional viscosity is explored. The numerical results obtained are in good agreement with the experimental findings.;Both head-on and off-centered collisions of drops are investigated using axisymmetric and three-dimensional simulations. In the absence of gravitational forces, the drops are accelerated toward each other by a body force that is turned off before the drops collide. As the drops approach each other, the film of fluid between them gets thinner, and when this layer is thin enough the contact interfaces are removed to allow the coalescence to occur. Depending on the collision energy and impact parameters, the drops may coalesce permanently or coalesce temporarily and then split again. If the interfaces are not ruptured, the outcome is bouncing without coalescence. |
