An Experimental Study On The Dispersion And Settlement Of Spilled Oil Under Wave Actions

Due to the frequent occurrence of marine oil spills,serious harm and economic losses have been caused to the marine ecosystem.After an oil spill occurs,part of the oil film will be broken by waves and enter the water body to form dispersed oil.Submersible oil and suspended particles in seawater form suspended or sedimented oil-suspended particle aggregates（OSA）.Suspended OSA will accelerate biological degradation and natural weathering,while sedimented OSA will be deposited on the seabed and affect benthic organisms at the ocean bottom.Living organisms will be subject to certain pollution and hazards.This thesis studies several factors that affect the formation of OSA,and provides theoretical support for the formation and prevention of sunken and submerged oil.In this thesis,a wave tank is used to simulate the real situation of the ocean.Five oils,including Oman crude oil,Iran heavy oil,Roncador crude oil,Merey crude oil and 180#fuel oil,are selected as experimental oils,and natural kaolin is used as suspended particles to study variation of sunken and submerged oil under different oils.The variation of the amount and size of the dispersed oil droplets of different oils,and that of the amount of oil contained in the settling OSA and its droplet size were studied.And on this basis,the influence of oil spill dispersant on the formation process of submerged oil is increased.The main research results are as follows:（1）When the water temperature is constant,the greater the viscosity of the oil,the more restrained the dispersion process of surface oil into the water,and the time taken for the maximum oil dispersion efficiency(ODE_max)is shortened.However,there is a threshold value for the viscosity of oil products,and the oil sinking efficiency of oils above this value decreases with the increase of viscosity;（2）When the water temperature changes,the dispersion efficiency of surface oil in water gradually increases with the increase of temperature.This is because the temperature changes the viscosity of the oil,which affects the dispersion efficiency of the surface oil;（3）When the amount of oil spill dispersant is within a certain range,the amount of dispersed oil in the water will rise to a certain extent.Once it exceeds this range,the amount of dispersed oil in the water will increase significantly,and the particle size of the oil droplets will decrease accordingly;（4）Appropriate addition of oil spill dispersant can effectively increase the formation of OSA,but excessive dispersant will enhance the strength of the interfacial film formed by the surfactant at the periphery of the oil droplet,and inhibit the polymerization between oil and suspended particles;（5）As the concentration of suspended sediment in the water increases,the ODE in the same period of time shows an increasing trend,and with the increase of mixing time,the value of ODE gradually increases until it stabilizes,mainly because the presence of suspended sediment reduces the oil-water interfacial tension;（6）Under the same time of wave action,the amount of oil contained in OSA increases with the increase of sediment concentration,and the proportion of OSA with larger particle size gradually decreases.These research results can provide a theoretical basis for oil spill prevention and prediction migration and transformation of oil spill.