Oil

Oil is a particular case of a chemically active substance. In the oceans, it is considered a pollutant by all means. It is not pure, but a mixture of compounds, each with specific properties. Generally, it will be a buoyant mixture immiscible in water with physical properties (density, viscosity) sensitive to its weathering history. It will be transported in the aquatic environment while spreading and weathering, i.e. evaporating, dissolving, biodegrading and emulsifying. Its speciation and weathering combined create a perfect setting for individual based modeling opportunities while offering huge challenges due to the complexity of processes and the number of parameters. Oil’s discrete representation in the particle world is called a Lagrangian parcel. A parcel may be floating at the surface or submerged as small droplets as described in the corresponding figure below. A surface parcel can be thought of as a spillet, i.e. a subdivision of a larger spill. Similarly, a subsurface parcel can be considered as a group of droplets. The motion is a combination of advection, dispersion and spreading as shown in the corresponding figures.

Here, we present three representative animations. They show OILMAP simulations of two real world spills and one hypothetical case. Basic information on the simulations are given in animation captions. They are kindly provided by Dr. Malcolm Spaulding, Professor Emeritus of Ocean Engineering at the University of Rhode Island, and RPS-ASA.

Processes for oil at sea. A sub-sea release is shown for generalization. Image provided by RPR-ASA, courtesy M. Spaulding.

 

An estimated 300 tons of oil was spilled from the Russian aircraft carrier Admiral Kuznetsov while refueling of West Cork, 63 km off the Irish coast on February 14th, 2009. Due to favorable winds, the spill did not make it to the Irish coast and followed an easterly path. This is the animation of the spill as modeled by OILMAP. The observed center of mass is marked by red stars on February 14, 22, 26 and 27. More on the incident can be found here.

On 26 June 2012, two cargo vessels collided in the Nancao Waterway in the vicinity of the Yangtze River Estuary. 60 tons of oil were spilled from one of the vessels.. Chinese government agencies used OILMAP to simulate the spill trajectory and fate of the spill. The model simulation results matched extremely well with the field data (affected shoreline length, spill area and timing) observed by the local responders. More on the incident can be found here.

This is a hypothetical spill of 1500 tons of fuel oil released of a period of 4 hours at the surface off the Long Island coastline. The spill makes landfall on the east side of Plum Island and then heads towards the Rhode Island Sound with tides and Global Forecast System winds. Hypothetical simulations such as this help us prepare better for emergency situations..

 

Representative horizontal advective and dispersive movement of spill parcels in a wind field with rotation in shallow water. There are four sequential times. Dot size scales with particle size. The plus sign shows the purely advective case. The 3-D version of this figure (given in the book) shows smaller particles spending more time at depth and lagging behind the larger and more buoyant ones that dominate the surface.

Breakup of a slick parcel into a submerged parcel of small droplets of diameter D. The process is driven by the turbulent energy ε. M, ρ and ν are the mass, density and kinematic viscosity respectively.

Release of two equal spill parcels in sequence, with displacement and spreading. Parcel 1 undergoes two steps. Parcel 2 is newer, undergoes only one step. Straight vectors show advective displacements. Squiggly vectors show random walk dispersion.