Coalescence and spreading of drops on liquid pools

• Published in: Journal of colloid and interface science 2021-03, Vol.586, p.257-268
• Main Authors: Kulkarni, Varun, Lolla, Venkata Yashasvi, Tamvada, Suhas Rao, Shirdade, Nikhil, Anand, Sushant
• Format: Article
• Language: English
• Subjects: Coalescence; Drop impact; Oil spills; Spreading
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2020.10.089

[Display omitted] Oil spills have posed a serious threat to our marine and ecological environment in recent times. Containment of spills proliferating via small drops merging with oceans/seas is especially difficult since their mitigation is closely linked to the coalescence dependent spreading. This inter-connectivity and its dependence on the physical properties of the drop has not been explored until now. Furthermore, pinch-off behavior and scaling laws for such three-phase systems have not been reported. We investigate the problem of gentle deposition of a single drop of oil on a pool of water, representative of an oil spill scenario. Methodical study of 11 different n-alkanes, polymers and hydrocarbons with varying viscosity and initial spreading coefficients is conducted. Regime map, scaling laws for deformation features and spreading behavior are established. The existence of a previously undocumented regime of delayed coalescence is reported. A novel application of the inertia-visco-capillary (I-V-C) scale collapses all experimental coalescence data on a single line while the early stage spreading is found to be either oscillatory or asymptotically reaching a constant value, depending on the viscosity of the oil drop unlike the well documented monotonic, power law late-time spreading behavior. These findings are equally applicable to applications like emulsions and enhanced oil recovery.