Weathering process and spreading of low sulfur fuel oil (LSFO) on water surface*

We investigated the weathering process (viscosity and rheological characteristics) of low sulfur fuel oil (LSFO) to understand its spreading dynamics on the water surface. First, we find that the viscosity dependency of LSFO on the temperature follows the William-Landel-Ferry (WLF) law. Then, through the emulsion test, we measured that the meso-stable emulsion, whose viscosity is 10-100 times larger than the normal condition, is achieved. On the other hand, the evaporation of LSFO is found to be so small that its effect on the properties is negligible in the tested conditions. In addition, we experimentally examined the spreading dynamics (e.g., the thickness of oil slick and spreading area, rate) of LSFO on the water surface in the circulating water bath, in which the wind speed, water temperature, and initial oil volume are controlled as 2-5 m/s, 5-25ºC, and 100-400 ml, respectively. The spreading speed rapidly increased after a critical viscosity (~ 500 cP) by the imbalance between the viscous retarding force and wind shear stress. Finally, based on the acquired weathering properties, we performed the numerical simulation with a length scale of hundred meters on the spreading of LSFO spills, which will help deal with the marine oil-spill accidents.