Abstract
Gas explosion can cause great structural damage to the semi-submersible platform, so understanding the gas explosion dynamics is critical to avoid the accident and its escalation to a major disaster. In this study, gas explosion experiments were conducted at a semi-submersible platform with dimensions of 3.09 m × 3.29 m × 3.46 m. Both pressure-time histories and flame evolutions were recorded from experiments. A 3D numerical model was developed in OpenFOAM and validated by experimental data. Numerical results show two flame regimes, and the transition between two flame regimes occurred close to the drilling and accommodation module, where congestion and confinement exist. The flame propagation is dominated by hydrodynamics instabilities, and it can be accelerated by congested obstacles. The transition between two flame regimes can induce the large local overpressure. For a long-distance ignition, the largest overpressure peak is located at the accommodation module of the offshore platform. For the ignition in the drilling module, a larger overpressure occurs at both the left and right edges of the main deck of offshore platform. For both ignition positions, the middle part of drilling derrick has the larger overpressure peak. This work provides theoretical support to design mitigation measures on semi-submersible platforms.