CFD modelling of pressurized gas releases: sensitivity analysis of driving parameters

The consequences analysis is a crucial aspect of the Risk Assessment, especially for Oil & Gas structures, where hundreds of accidental scenarios must be simulated. This work investigates the accidental release of high-pressure flammable gas in a congested offshore environment considering multi-physics and multi-scale nature of the phenomenon. Initially, the flow results supersonic with compressible effects and then it evolves in a subsonic dispersion. To handle this change of physics, a Computational Fluid Dynamics (CFD) two steps approach is developed at the SEADOG laboratory in Politecnico di Torino. This approach imposes two simulations: the first one considers the compressible phenomena in a small domain called Source Box (SB), the second one considers the gas dispersion in the platform. The advantage is to use the results of the first simulation as an input for several dispersion simulations. The aim is to compile a library of plausible SB and to evaluate the consequences of an accidental scenario selecting the proper SB for the dispersion simulation, allowing a timesaving. This work is focused on the optimization of the number of SB to construct a SB library. The objective of this work is to achieve a sensitivity analysis on the input parameters (release pressure, hole diameter, distance and dimension of an obstacle inside the SB) in order to optimize the number of SB to be simulated reducing the computational effort.