Underwater gas release modeling and verification analysis

Abstract

Accidental subsea gas releases may cause an underwater gas plume migrating from the seafloor to the sea surface, which may pose offshore fire hazards or instability of ships. Numerical simulation is an efficient approach to model the underwater gas behavior and support risk assessment. To verify the availability of numerical modeling methods for the underwater gas release, this paper establishes a small-scale experiment system to simulate the underwater gas release, and several experiments with the typical conditions are conducted to obtain the plume parameters, e.g. shape, radium and fountain height. Two CFD models, i.e. Eulerian-Eulerian and Eulerian-Lagrangian approaches, are used to reproduce underwater gas plumes in the experimental conditions. The comparison between simulations and experiments is conducted to analyze the effectiveness and the rationality of numerical modeling methods. The results indicate that simulations with two methods are overall consistent with experiments. However, a detailed comparison reflects that Eulerian-Eulerian model cannot satisfactorily capture the transition of jet to plume and the entrainment during gas rising. In contrast, the results from Eulerian-Lagrangian model are better in agreement with experiments. This study verifies these two numerical modeling methods through a small-scale experiment. The validation against full scale tests is suggested in future work to use it as a reliable tool for risk assessment of subsea gas release incidents.