Modelling of Vented Gas Explosions in the CFD tool FLACS

Accidental explosions occurring in enclosures can be efficiently mitigated by installing pressure relief panels. The venting process enables the combustion products to expand without subjecting the main structure to destructive overpressures. However, the pressure development in time will be the result of several physical phenomena, interacting in different ways depending on parameters such as the vent size, the ignition position, the panel opening pressure, the vent panel mass per unit area, the presence of obstacles, the layout of the chamber, and the combustion properties of the fuel. Due to the complexity of the problem, it is difficult to produce one universal venting guideline for all cases. In principle, detailed CFD (Computational Fluid Dynamics) simulations should allow for the representation of all physical processes affecting vented explosions, thus allowing for a consistent prediction of the expected overpressure loads. A series of experiments performed at FM Global (Bauwens et al., 2010) have been simulated using the CFD tool FLACS. The results show that some of the pressure generating mechanisms are represented well, while others are not modelled properly. The relevance of representing each phenomenon for the final application of FLACS is discussed.