| Marine oil spills have caused great harm to human health and marine ecological environment.In order to fully grasp the movement mechanism and process of oil droplets in the sea,it is also necessary to study the dynamics in the processes of sinking and flotation of oil droplets during the weathering process,so that the marine oil spill accidents can be comprehensively forecasted and analyzed,and scientific and targeted measures can be developed.In this paper,two weathering processes(evaporation and dispersion),which have significant impact on the submergence of some representative oils are studied to further understand the mechanism of the impact of weathering on the submergence process of oil spill,and experimental data for marine oil spill prediction are provided.The specific research content and conclusions are the followings:(1)The relationship between the density of four Bohai crude oils(YYH,YYS,SJH and SLY)and their respective asphaltene and wax content at different temperatures,as well as the relationship between their viscosity and their respective asphaltene content at different temperatures have been obtained.The results can be used in the prediction of the oil density during the weathering process of the oil,when the environmental conditions and the composition of the oil change,in order to determine whether the oil can sink in the water body or not due to its density.Similarly,the prediction of the oil viscosity during the weathering process can consider the change of oil properties in the oil behavior prediction,which can improve the accuracy of oil submergence behavior.(2)According to Fingas theory,the shallow disk evaporation experiment was carried out to test the evaporation kinetics of four oils of Bohai Sea at different temperatures.The results show that the relationship between oil YYH evaporation rate and time ln(?)in the logarithm form satisfies a linear equation.For the other three oils,their evaporation rate and time ?1/2 in the exponential form satisfies a linear equation.The characteristic of the components of the oil are correlated with the form and parameters of the equations and the results help to establish an equation through the characteristic of the oil components in the absence of experimental data.In the case of irregular effect of temperature on oil evaporation rate,it is proposed that the oil evaporation kinetic equation be established 3 hours after the occurrence of the oil spill,which can reduce the sensitivity of prediction results to temperature influence.(3)Using a small baffle flask to investigate the impact of wave intensity,duration of wave action,dispersant,and standing time during sinking and flotation of Liaohe crude oil and fuel oil 180,it has been found that:the intensity of the wave action and dispersant content have a large impact on the sinking rate and the stability of the sinking,they have a threshold effect.The wave action time has a maximum value,after reaching its peak the effect of the floatation and sinking of oil will be reduced,and the dispersant effect is time-efficient.A piecewise modeling suggestion is proposed:the conditional threshold and time segmentation under the condition of continuous wave action should be considered.(4)The characteristics of the fuel oil 180 during the wave breaking process has been investigated,the wave breaking and entrainment effect of the oil has been analyzed,and it was found that the stretching of the wave action enhances the expansion of the oil film,and causes the broken parts of oil to separate,be dispersed,not squeeze back together(to form coalescent parts of oil).The root cause of the tensile action is the water flow velocity gradient,suggesting a combination of the extended equation for the simulation of oil breaking. |
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