Application of computational fluid dynamics modelling in the process of forensic fire investigation: problems and solutions

Fire modelling has been gaining more and more interest into the community of forensic fire investigation. Despite an attractiveness that is partially justified, the application of fire models in that field of investigation rises some difficulties. Therefore, the understanding of the basic principles of the two main categories of fire models, the knowledge of their effective potential and their limitations are crucial for a valid and reliable application in forensic science. The present article gives an overview of the principle and basics that characterise the two kinds of fire models: zone models and field models. Whereas the first ones are developed on the basis of mathematical relation from empirical observations, such as stratification of fluid zones, and give a relatively broad view of mass and energy exchanges in an enclosure, the latter are based on fundamentals of fluid mechanics and represent the application of Computational Fluid Dynamics (CFD) to fire scenarii. Consequently, the data that are obtained from these two categories of fire models differ in nature, quality and quantity. First used in a fire safety perspective, fire models are not easily applied to assess parts of forensic fire investigation. A suggestion is proposed for the role of fire modelling in this domain of competence: a new tool for the evaluation of alternative hypotheses of origin and cause by considering the dynamic development of the fire. An example of a real case where such an approach was followed is explained and the evaluation of the obtained results comparing to traces revealed during the on-site investigation is enlightened.