This paper presents Computational fluid dynamic (CFD) studies on leak size effect towards the time taken for migration of oil droplets to reach free surface upon leakage. The size of the leakage hole (d) is a variable ranging from 0.1 m to 0.3 m with increment of 0.1m whereas the other parameter is fixed. A computational rectangular domain with length of 20m and height of 15m was simulated in Gambit 2.4. The length of computational domain is large enough, which is larger than the longest horizontal distance the oil droplets migrate when they reach the sea surface. In the Gambit 2.4, the time taken for the oil droplets to reach free surface was observed by varying the leak size; d1=0.1m, d2= 0.2m and d3=0.3m respectively. . The outer diameter (D) of damaged submarine pipeline is 0.5 m. The mesh was generated and exported to Fluent. Using the formulas we can obtain when and where to see oil reaching the sea surface, and conduct rapid response the maximum horizontal migration distance of oil at certain time is predicted, and a forecasting model is proposed. These calculated results will provide useful guidance to place the oil containment boom. Results were observed at 1000 number of time steps (iterations) with a step size of 0.1s. For the leak size 0.1m, the time taken for the oil to reach the free surface is 64s. For leak size 0.2m, , the time taken for the oil to reach the free surface had decrease to 55s. On the other hand, for the large leak size 0.3m, time taken for the oil to reach the free surface had decreased to 52s. As the conclusion, the leak size of pipeline can affects the time taken for oil to reach free surface upon leakage in pipeline
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