A Review of the State - of - the - Art in Gas Explosion Modelling HSLl 2002102

Objectives 1. To identify organisations involved in gas explosion research in the U.K. and Europe. 2. To survey these organisations, to determine their areas of current and proposed work. 3. To collate their responses in a report, which also provides an up to date literature review of gas explosion modelling. 4. To critically assess the strengths and weaknesses of available gas explosion models. 5. To recommend areas where fkther work is needed to improve the accuracy of the gas explosion models. Main Findings I. There are a wide range of class of models available-from empirical and phenomenological, through to those which are Computational Fluid Dynamics (CFD) based. The latter category falls into two areas: 'simple'-many obstacles not resolved and 'advanced'-all obstacles resolved by the 3-D CFD grid. 2. Generally as one moves from empirical to advanced CFD, models become based on more fundamental physics, are able to more accurately represent the real geometry, but require increasing resource to setup , run and interpret the results. 3. Models in each class embody a number of simplifications and assumptions, limiting their ability to be used as reliable predictive tools outside their range of validation against test data. It appears that only those models falling into 'advanced' CFD class could in principle be capable of being truly predictive tools outside their immediate range of validation. However, even here the existing models have limitations and require further development and testing before this capability is fully realised-which even then will currently be limited to relatively simple geometries by the required computer resources. 4. Many of the CFD-based explosion models in current use employ relatively crude approximations of the modelled geometry, relying on calibrated sub-grid models. 5. Most of the 'simple' CFD codes and some of the 'advanced' CFD codes most commonly used for explosion prediction use simple, dated numerical schemes for both the computational grid and the finite differencing, which could lead to substantial numerical errors. An agency of Ule Health and Safety Executive 6. The combustion model used in CFD-based approaches to predict the reaction rates are also subject to a considerable degree of uncertainty. Models, which employ prescribed reaction rate, could be more sound than those relying on an Eddy Break-Up model, because the latter requires a resolution of the fl m e front unlikely to be achieved in practice. Work is currently under way on the incorporation of detailed chemical kinetics into …