【作者】 郭为军；

【导师】 王永学；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2011， 博士

【摘要】 溢油事故会对海洋环境造成严重破坏,为了全面了解评估溢油过程,人们对模拟溢油轨迹和归宿的溢油模型开发已经做了大量工作。本文简要介绍了海上石油污染的现状及其危害,并对近海水动力学和海上石油的行为与归宿数值模型的基本理论与发展现状做了详细的综述。在此理论基础上,建立了三维海面溢油迁移转化预报模型。近海溢油行为受风、波浪和潮流等环境动力因素影响,因此首先要精确模拟出这些动力因素。为了精确描述近岸复杂流场,本文使用三维水动力模型POM和第三代近海波浪模式SWAN模拟了近海波流耦合作用下的三维水流。首先引入Mellor以线性波理论推导的垂向三维辐射应力公式,讨论了辐射应力在不同水深情况下的垂向变化规律,结果表明辐射应力主要集中在自由面附近。将三维辐射应力加入到三维水动力模型中去,研究了近岸波浪破碎引起的增水和底层离岸流现象。计算结果和实验资料相吻合的结果表明,考虑三维垂向三维辐射应力的水流模型能够对近海水动力现象进行准确的模拟。溢油在海上经历着漂移、扩散、扩展、垂向离散、蒸发、乳化、溶解等及其相互作用的复杂过程,这些过程可以简略地概括为输运和风化过程。最近的海洋观测显示海上物体漂移轨迹具有用普通布朗运动无法描述的分形结构,油膜在海水表层运动也有加速扩散的趋势。因此,在模拟扩散过程时,利用分数布朗运动模型来描述油膜的超扩散现象。数值实验表明,当Hurst指数取0.75时,可以取得较好模拟结果。在证实了粒子跟踪模型和浓度模型的等价性后,本文提出了粒子跟踪-浓度混合模型来模拟溢油过程。油以油粒子的形式从源强处排放,当油膜厚度或者油滴浓度低于临界值时,油粒子转为所处网格上的浓度。油粒子消失后,以欧拉-拉格朗日模型来计算浓度。为了获得三维溢油模式,利用Langeven方程描述油粒子在垂向的运动。结果表明,浮力和垂向湍流强度是油滴垂向运动的重要因素。将输运模型和风化模型相结合来预测溢油表层运动,油滴的垂向分布,水体中油浓度以及油组分之间的平衡。用此模型模拟大连附近海域“阿提哥”号油轮溢油事故,数值模拟结果和卫星观测数据吻合良好。更多还原

【Abstract】 Accidental oil spills have the potential to cause serious impact on the marine environment so that considerable amounts of work have been directed towards developing spill models predicting the trajectory and fate of spilled oil in order to understand and quantify the spill processes. In this paper, the present situation of marine oil pollution and damage are briefly introduced, and the comprensive review of coastal hydrodynamics and oil spill numerical modeling is given. On the theory basis, the three-dimension oil spill numerical model is proposed.The behavior of oil at sea is determined by the environmental conditions involving sea winds, waves and water currents. Accurate environment information is essential for the reliable prediction of the transport and fate of oil pollution, so forecasting these dynamic factors accurately is the base of the oil spill model. A high-resolution circulation model describing the complex hydrodynamics of coastal waters is required to provide appropriate flow fields. For this purpose, the sigma-coordinate primitive equation Princeton Ocean Model (POM) coupled with a third-generation wave model for coastal regions SWAN (Simulating WAves Nearshore) has been employed. Expressions for depth-dependent radiation stresses derived on the basis of linear wave theory by Mellor are introduced. The radiation stresses at different water depths are discussed, and the result demonstrates that the wave radiation streeses concentrated near the free surface. By adding the depth-dependent radiation stresses to the POM threee dimensional flow model, the wave set-up and undertow are studied. A comparison of the numerical results with the experimental data shows good conformity. It shows that the three dimensional flow model with the depth-dependent radiation stresses can be applid for the coastal hydrodynamic problems.The main mechanisms which govern the fate of an oil slick are advection, diffusion, mechanical spreading, vertical dispersion, evaporation, emulsification. dissolution and the interactions of these processes, which can also curtly recapitulate two modules- transport and weathering. Recent studies have shown that the trajectories of drifters on the ocean surface have a fractal structure that is far from being described using ordinary Brownian motion. Thus, in modeling the diffusion process, a discrete method has been employed for the generation of fractional Brownian motion (fBm) to illustrate superdiffusive transport. The numerical experiment demonstrates that when the Husr value equals 0.75, the simulated results are more consistent with the observations.After proving the equivalence bewteeen a particle tracking model and a concentration model, a hybrid particle tracking/Eulerian-Lagrangian approach for the simulation of spilled oil in coastal areas. Oil discharge from the source is modeled by the release of particles. When the oil slick thickness or the oil concentration reaches a critical value, particles are mapped on slick thicknesses or node concentrations, and the calculations proceed in the Eulerian-Lagrangian mode. To obtain a three-dimensional oil model, a mathematical description of the vertical movement of an oil droplet in the ocean is proposed based on the Langeven equation. The results manifest that the buoyant effect and the vertical turbulent variations are very important mechanisms for vertical movement of oil in the water column. The transport model is used to join other weathering modules for the prediction of the the horizontal movement of surface oil slick, the vertical distribution of oil particles, the concentration in the water column and the mass balance of spilled oil. An accidental "Arteaga" oil spill near Dalian coastal waters is simulated to validate the developed model. Compared with the satellite images of oil slicks on the surface, the numerical results indicate that the model has a reasonable accuracy.更多还原