Three dimensional interaction of two drops driven by buoyancy

The type of fluid drainage that occurs between two drops depends on the Bond number and viscosity ratio. At a small Bond number, drainage takes place only with first method. For large Bond numbers, drainage changes to the second mode. Only for moderate Bond numbers all three methods can happen. Inertia affects collision of drops at small Bond numbers (more rigid drops). It is found that inertia effects cannot be neglected at small Bond numbers, and the separation distance obtained does not agree with simulations performed at zero Reynolds number. Also, the collision of two drops at early stages of interaction is influenced by the Reynolds number. The viscosity ratio affects the onset of dimple formation in the interaction process. At a low viscosity ratio (0.2) the separation distance increases with the Reynolds number. The dimple formation is enhanced with increasing the viscosity ratio, and it occurs at a larger distance from the axis of symmetry.