Incipient motion of sand and oil agglomerates
After the Deepwater Horizon oil spill, oil which was released into the Gulf of Mexico reached the shorelines and mixed with sand in the surf zone to form sand and oil agglomerates (SOAs). These cm-sized particles are heavier than water and are therefore found on the seabed. Years after the initial formation of these particles, they keep appearing on the beaches, despite earlier cleanup. Several studies to the formation and transport of these particles have been conducted, but traditional shear-stress based formula, which are generally used for sediment transport, do not predict the mobility of SOAs well. This study focuses on the incipient motion of SOAs and has as goal to propose an improved method of predicting SOA mobility.
The approach of this study consists of two steps. First, the governing mechanisms of incipient motion are determined and the forces acting on the particles are found. With these forces, force and momentum balances are constructed. The second step consists of modelling the flow around a singe sand and oil agglomerate with a 2DV numerical model, for both spherical and disc-shaped particles. The findings from this can be used together with the force balances to predict incipient motion.
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