The proposed research aims to tackle the extremely complex problem of flame acceleration, the conditions for transition from turbulent deflagration to detonation and detonation. These physical phenomena are highly multidisciplinary which involve fluid mechanics, combustion, shock dynamics and detonation. We will start with small scales for model development and validation. In such analysis advanced combustion models for flame acceleration will be coupled with detailed chemistry together with special measures to tackle the stiffness issues associated with the chemistry. On this basis, modelling techniques will be developed for large scale problems using simplified chemistry. The key objectives of the proposed research, which is tailored for the Fellow to transfer knowledge to the host and/or bring knowledge to Europe, are as follows:• To deliver a robust sub-model for predicting flame acceleration around obstacles on the basis of the coherent flame model which is a variant of the flame surface density approach;• To validate the above model with laboratory scale test data and DNS predictions;• To apply the above model to examine flame acceleration in vapour cloud explosions, and examine in particular the effect of repeated obstacles on flame acceleration and possible transition to detonation.• To implement a reaction model and combine it with fine tuned chemistry to predict vapour cloud detonation pressure and velocity.• To test and validate the model with large scale detonation test data.• To apply the above model to analyse some recent proprietary experimental data from industrial collaborators, previously published test results as well as historical accident scenarios in which there was strong possibility that large vapour cloud detonated. In particular the effect of cloud height and thickness on the development of overpressure and its decay will be examined.• To draw conclusions and guidelines from the research.