Numerical Modeling of Oil Slicks Transport using Finite Volume Method with Wet-Dry Fronts

Hydro-environmental transport of oil spills has been simulated by Finite Volume Method.Eulerian approach is applied across the model, based on non-linear shallow water Reynolds-Averaged Navier-Stokes (RANS) equations, and effects of Coriolis force, viscous terms, surface wind stresses and bed friction stresses are included. The standard k–ε model gives a turbulence model for the mean flow structure. Wet-dry fronts are treated whitin the numerical model. Thenew model deploys many significant processes: advection, surface spreading, evaporation, dissolution, and emulsification. In this work, a highly-accurate algorithm based on a 4th degreeaccurate shape function has been used for the hydrodynamic model, which is not present insimilar models. The fate and transport of oil spilled in water is dominated by complex physicochemical processes that depend on oil properties, hydrodynamic and environmentalconditions. The evaporation process, together with dissolution and the mousse formation, leadsto an increase in the volume and density [6]. Oil transport, oil exploration and oil storage facilities are all possible sources of spills. The 1991Persian Gulf (Kuwait War) oil spill was estimated at 143 million liters or 38 million gallons [1]. The fate and transport of spilled oil is governed by the advection due to current, wave and wind;horizontal spreading of the surface slick due to turbulent diffusion, gravitational, inertia, viscousand surface tension forces; emulsification; weathering processes such as evaporation, dispersion and dissolution; interaction of oil with shoreline; photochemical reaction and biodegradation.The chemical and biological processes generally occur a long time after the oil spill [1]. Tkalich[15] applied a consistent Eulerian approach across the model; the slick thickness is computed using layer-averaged Navier-Stokes (LNS) equations, and the advection-diffusion equation isemployed to simulate oil dynamics in the water column. To match the observed balance betweenadvection, diffusion and spreading phenomena, a high-order accuracy numerical scheme isdeveloped. Wang and Shen [16] showed that the amount of oil released at sea is distributedamong a large number of particles tracked individually. Oil particles are driven by a combination of current, wave and wind induced speed and move in a 3D space. Horizontal and vertical diffusion are taken into account using a random walk technique. Perianez [13] developed anumerical model that simulated the dispersion of contaminants, including oil spills, in the Sea. The hydrodynamic was solved in advance and includes a barotropic model for calculating tides and a reduced gravity model for the average circulation. Dispersion was calculated using2 particle-tracking methods. Turbulent diffusion and specific processes for contaminants (for instance decay, biodegradation or oil evaporation) were simulated by Monte Carlo techniques. Guo and Wang [6] developed a hybrid particle tracking by an Eulerian-Lagrangian approach forthe simulation of spilled oil in coastal areas. To acquire accurate environment information, the model was coupled with the 3D free surface hydrodynamics model; Princeton Ocean Model (POM) and the third generation wave model; Simulated Waves Nearshore (SWAN).By simulating the oil processes, it has the ability to predict the horizontal movement of surface oil slick, vertical distribution of oil particles, oil concentration in the water column and mass balance of spilled oil.

Keywords:

Reynolds-Averaged Navier-Stokes , Alternating Direction Implicit (ADI) , Oil Slick , Finite Volume Method , k-ε turbulence model , Wet-dry fronts , Penta-Diagonal matrix , KPENTA algorithm