Comparison of oil slick and drifter motion at OHMSETT wave tank

In the aftermath of the Deepwater Horizon oil spill, thousands of ocean drifters were deployed in order to better understand the pathways and dispersion processes that drive oil slicks from the deep ocean to the coastline. Most of the drogued drifters released had a 0.60 m draft, hundreds of undrogued drifters had a 0.05 m draft, and thousands of drifting bamboo plates had a draft of 0.017 m. But typical slick thickness is 0.01 m or less, which raised an important question to interpret the ocean datasets correctly: how drifters move compared to oil slicks? The experimental study presented here addresses this issue by quantifying the differences, in terms of advection and diffusion, between the motion of oil slicks and the three groups of drifters mentioned above. Oil and drifters were released side-by-side in a vertically sheared flow controlled by waves produced in the National Oil Spill Response Research and Renewable Energy Test Facility (OHMSETT) wave-tank in April 2016. Trajectories were recorded by an aerial camera with spatial accuracy of 1.5 cm. The trajectories of each material patch were analyzed in details to determine how fast they were advected, but also how fast they spread and in which direction.