Master of Science (MS)
During the ‘Deepwater Horizon’ accident, dispersants were used as one of the remediation methods to mitigate the ill effects of oil that entered the water column. The dispersants lower the interfacial tension at the oil-water interface and cause the large oil droplets to disintegrate into finer droplets which remain dispersed in the water column for longer times. A dispersant typically is composed of a surfactant and solvent. Surfactants are chemical compounds which are chiefly responsible for the lowering of interfacial tension at oil water interface. In this study, we have investigated the effect of surfactant on the dynamics of a single crude oil droplet released into the quiescent water column. Experiments have been conducted in a tank with a capacity of about 100 liters, with an oil droplet being released through a nozzle. The droplets ranging from 0.3 to 0.85 cm were produced from three different nozzles. The shape adopted by the emanating droplets varied from spherical to oblate. On addition of the surfactant, sodium dodecyl sulfate (SDS) to water column there occurs reduction in interfacial tension at oil water interface which causes the droplet to flatten. SDS concentrations in water phase were varied in the range from 0 to 750 ppm. The change in the dynamics of the droplet due to the surfactant action has been reported in terms of the departure of the value of rise velocity and aspect ratio from that observed for a rising droplet in absence of surfactant. All experiments were conducted in ambient conditions. The second aspect of this study presents a numerical model based on finite volume method, which emulates the experimental observations. Volume of fluid method has been used for tracking the oil-water interface. The interfacial tension at the oil-water interface at various concentrations of surfactant is measured by Pendant drop Method using the Axisymmetric Shape Drop technique and has subsequently been used in the simulations. The model developed can be used to predict the behavior of droplets released into the water column during the oil spill.
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Rao, Abhijit, "Effect of Surfactant on Dynamics of a Droplet Released in a Quiescent Medium" (2013). LSU Master's Theses. 1925.