The spreading dynamics of small oil drops over nanofiber layers has been investigated to improve the oil spill management process. Although liquid transport studies have been used to compare different substrates, the actual effect of the fibrous substrate structure has not been precisely investigated. Nanofiber substrate structures consist of micro- and nanocapillaries that vary in diameter and length and are interconnected in a complex manner. Migration of a liquid from one layer to another as well as on the same layer is an important part of the sorption process in nanofiber substrate structures. In this work, the problem under investigation provides spreading small oil drops over a thin porous layer nanofiber until saturation. An experimental evolution describing the drop spreading has been deduced, which shows the speed of spread of the oil drop is significantly affected by the substrate areal weight. The oil drop area over a dry porous layer seems to be caused by the interchange of two spreading velocities, one over the layers and the other penetration of the oil drop through the pores of the substrate. The higher the oil spreading speed, the lower the permeation of the oil into the porous nanofiber substrate and vice versa. To increase the absorption of the nanofiber substrate, adding a nonwoven thin film to cover the nanofiber layers was studied. It was revealed that the presence of such film significantly accelerates the oil-drop spreading speed by up to 300% and reduces the overall time of the oil drop's life.
Drop spreading and drifting on a spatially heterogeneous film: capturing variability with asymptotics and emulation
