A simulation model was developed to predict spilled oil transport on the water surface using particle tracking method of Port and Airport Research Institute (PARI) for helping oil recovery by oil recovery ships, named OIL-PARI. The OILPARI formulates three major factors that affect the floating oil movement, the oil advection, the mechanical oil spreading, and the oil diffusion terms. This paper is intended the latter two terms.
　First is the mechanical oil spreading term. We conducted the mechanical oil spreading experiments and the results were compared with Fay’s model (1969, 1971). As a result, oil slick spreading velocity was well simulated by the Fay’s third stage model of surface tension - viscous region when the oil slick thickness is smaller than 10⁻⁴ m. The spreading coefficient of Fay’s third stage model was also derived. Next, we developed a new simulation model to calculate the effect of the net surface tension and oil buoyancy to modify the random walk technique and Fay’s model to meet the particle expression.
　Second is the oil diffusion term. A diffusion model at the sea surface was constructed to predict the turbulent diffusion coefficient of spilled oil, referring results from in situ drift experiments using pseudo oil made of sponge rubber. And we discussed the adaptively about derived diffusion model.
　And also, we discussed the validity of the simulation model. To verify the new model, hindcast simulations were applied to the three actual oil spill incidents. First, Hebei Spirit oil spill incident, which occurred offshore from the Taean coast in South Korea in 2007, was simulated and the result was compared with observed ones of oil gravity position and oil area. Second, we simulated Diamond Grace oil spill incident, which occurred in Tokyo bay in 1997, we discussed oil advection area from observed and simulated results. And third, we simulated Beagle 3 oil spill incident, which occurred at the mouth of Tokyo bay in 2014. The error of oil gravity position between observed and calculated results was about 1 - 2km, and advection velocities were almost same between them.