Coalescence Between Adjacent Drops Lying on the Interface of Two Liquids

Some industrial processes, in their operations, involve the presence of two immiscible liquid phases. The dispersed drops are surrounded by a continuous phase. The drops tend to coalesce with adjacent drops or to join their mother phase separated by an interface. These kind of phenomena occur in many industrial operations as well as in environmental processes. The liquid-liquid foams behaviour is connected to them. Literature has devoted some attention to the problem of drop coalescence, mainly for the case of coalescence of a single drop through planar surface (Charles and Mason, 1960; Hartland, 1967; Davis et al., 1971; Zulfaa and Longmire, 2004; Chen et al., 2006; Aryafar and Kavehpour, 2006, Blanchette and Bigioni, 2006). Some research has been also devoted to the coalescence of adjacent drops (Chen and Pu, 2001; Zdravkov et al, 2003). This work reports the results of some experiments performed in a water-in-oil system. The coalescing drops (Figure 1) has been captured by using a camera and the coalescence time measured. A model has been proposed and compared with the experimental data. The reported approach concentrate the attention on the relevant importance of the Van Der Waals/London intermolecular attraction forces and describes also the effects of the deformation of the interface area contained between the two drops.