| Once submarine oil pipeline leaks the marine will be harmed seriously and this damage may be long-term harm for marine. Timely and accurate leak detection method and grasping oil spill rules can provide the necessary theoretical guidance for pipeline leak emergency strategy and reduce the extent of the damage to the environment for oil spill. This paper will study in submarine oil pipeline leak detection method and underwater oil spill spread rules.This paper has studied the essence of oil pipeline leak from view of fluid dynamics aiming at the problem of submarine oil pipeline leak detection. The submarine oil pipeline leak detection mathematical model has developed basing on the theory of fluid dynamics and thermodynamics, and effective solving methods has explored. The model achieves submarine oil pipeline leak detection, positioning and predicting the spill volume. Finally, submarine oil pipeline leak detection software has been developed.This paper has analyzed the oil spill spread process underwater after submarine oil pipeline leak occurring aiming at the problems of spill oil spread. The oil spill spread process can be divided into two stages.The first stage happens in short time after the leak. The spill oil jets in water and spill oil mainly controlled by the initial momentum in this stage.The time that the second stage happens is from the end of the first stage to the first spill oil droplet up to the sea surface. The spill oil is controlled by momentum and sea currents together and its initial momentum weakens in this stage. The mathematical model was established, VOF multiphase flow equations of the model and the standardized k-e turbulence model are introduced. The finite volume method discrete control equations, and PISO algorithm calculates the flow field. Finally, spill oil spread process of two stages is simulated in FLUENT software.The main conclusions based on all study are as follows:(1) Leak detection and positioning:①three different boundary conditions are established, and traditional characterized line method is used to achieve submarine oil pipeline leak detection;②aking full advantage of the flow, pressure and temperature of the start and end of the pipeline at the same time based on the improved method of characteristics line method gets two different pressure drop curves along pipeline, and the intersection of the two pressure drop curves is the location of the pipeline leak.(2) Oil leak volume calculation:this paper develops a method for residual oil leak volume calculation after the valve shut. Residual oil leak volume after the valve shut is calculated by introducing boundary conditions of valve shut and leak boundary, and combining with the solving information before the valve shut. The oil leak volume before valve shut is solved by improved characteristics line method.(3) Subsea oil pipeline leak detection software is developed in C sharp2010, the result of an example by software shows that the result is in accordance with the oil pipeline leak fact. It verifies the correctness of the mathematical model and solution methods.(4) Simulating and analyzing the impact of the oil jet velocity and leak hole diameter to the oil jet:①he greater leak diameter and oil jet velocity are at the same time, the longer leak oil column will be;②the greater leak hole diameter is, the greater diameter of oil column will be, and at the same oil jet velocity both sides of oil column are from without plume to appearing a significant plume; However, when the oil jet velocity is below a certain value the plume will not appear;③with leak hole diameter increasing, oil column becomes from without necking to appear a significant necking.(5) Simulating and analyzing the impact of leak velocity, leak hole diameter and sea current velocity for the spread of oil spill:①the more oil droplet number is, the wider oil pollution range is; The larger sea current velocity and the smaller leak hole diameter and oil leak velocity are; the more oil droplet number will be.②the greater oil leak velocity is, the shorter time of spill oil reaching sea surface and the more serious extent of oil pollution will be; The smaller oil leak velocity is, the more number of oil droplet will form, and the wider oil pollution range will be;③the greater leak hole diameter, the shorter time of spill oil reaching sea surface will be; In contrast, the more number of oil droplet forms, and the wider oil pollution range will be;④the greater sea current velocity is, the longer time of spill oil reaching sea surface and the wider oil pollution range will be. Sea current is the main factor affecting the spill oil spread. |
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