Abstract
Accidental subsea releases are a matter of concern in the oil and gas industry. It may halt the production and lead to a flammable gas cloud on the sea surface close to the spider-deck of oil rigs. The ignition of the flammable cloud is not desirable. The proper prediction of flammable gas volumes from subsea releases is of paramount importance to reduce the level of risk. It also helps the elaboration of emergency plans. The use of Computational Fluid Dynamics (CFD) is proved to be an efficient, safe, and relatively low-cost tool applied to analyze the gas plume dynamics underwater. Motivated by the scenario of real accidental subsea gas releases, this work studied the behavior of submerged gas plumes in a 9 m x 7 m 2D computational domain representing a water tank. The case setup, which was validated against experimental data in previous works, considered the Eulerian-Eulerian approach with the Volume of Fluid (VOF) multiphase model. The study simulated different leak sizes and leak rates, aiming to evaluate if there was a relation between the Reynolds numbers and the geometrical features of the resultant plume, such as rising time, fountain height at the rising time, fountain heights after 15 s of the release and horizontal dispersion distance. For all the plume parameters there was a relationship between their behavior and the leak Reynolds number, and, especially for rising time, and fountain heights, this relation showed independence from the leak size. This indicates that, at least for the considered size of the water column, the Reynolds number of the can be the main parameter considered when determining these plume properties at the surface. This study is valuable to support the development of mitigating measures in the case of an accidental gas release underwater.
