Numerical simulation of gas explosions in complex geometry

The flame acceleration in the presence of complex geometry is an important issue as far as explosions within industrial environments are concerned. A high level of confinement due to obstacle congestion often characterises chemical plants handling flammable gases. In the case of gas explosion, this feature leads to strong acceleration of the flame and the generation of very destructive blast waves. Empirical methods such as the Multi-Energy method are commonly used in order to quantify the possible damage of explosions. Computational fluid dynamics (CFD) is an emerging technique to predict the consequences of gas explosion and it is often considered a powerful and accurate tool to obtain detailed analyses of the flame propagation. However, systematic analysis of the reliability of the employed models is still needed. Aim of this work is to contribute to the assessment of CFD codes employed for the simulation of gas explosions. Two commercially available CFD codes, namely AutoReagas and STAR-CD codes, have been considered in this study. Their ability to simulate the flame acceleration within obstacle-filled tubes, filled with different flammable gas-air mixtures, has been investigated. For this configuration extensive experimental investigation showed that about all the physical effects that influence the flame acceleration phenomena are present. Moreover, it is possible to define a steady flame velocity for different propagation regime, which can be considered as a global parameter to promptly compare the numerical predictions and the experimental data. Comparison of the results obtained by means of the two codes have been performed and some restrictions to the use of codes with respect to the fuel-air mixture composition.