Current gas-freeing processes on board Very Large Crude Carriers (VLCCs, ships ranging from 160,000 to 320,000 dwt) typically take 2–8 hours depending on the state of the tank. Legislation and practices covering the operations do not account or advise for the varying configurations of the tank leading to potentially inefficient de-gassing of the tank. Through the use of computational fluid dynamics (CFD), it has become possible to examine and analyse the important physical phenomena that governs the de-gassing processes inside the tank. The work presented utilises CFD to visualise the flow interactions of the injected air and the fluid inside the tank in combination with the tank structure. Using these modern techniques, existing gas-freeing methods can be examined with a view to highlighting poor mixing areas. A number if various tank configurations are examined, with respect to size, geometry, vent and fan arrangements. The results are analysed and presented with recommendations.

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