“Scaling-up” fire spread on wood cribs to predict a largescale travelling fire test using CFD

Simulation-based approaches for characterising the fire behaviour of travelling fires in large compartments are a potentially valuable complement to experimental studies, providing useful insights on evolving boundary conditions for structural response. They are attractive in reduced costs and the possibility of carrying out systematic parametric studies free from some of the experimental uncertainties, but sufficiently general models have not been previously demonstrated. Here, we explore the potential for “scaling-up” a “stick-by-stick” CFD model which had been carefully calibrated against the results of experiments on an isolated crib, of 2.8 m diameter, to a uniformly distributed fuel bed of extent 4.2 × 14.0 m located within an open compartment 9 × 15 m in plan, with an internal height of 2.9 m. The results in terms of the fire spread and burn out predictions are very encouraging, and the heat release rate evolution is also consistent with the experimental value. There are some discrepancies in predicted gas phase temperatures, nevertheless, such discrepancies with this aspect of the model are unlikely to have any great significance in the prediction of fire spread on a horizontally orientated flat fuel bed, which is the prime interest of the current work. Thus, the established “numerical simulator” looks to have good potential as a tool to explore and characterise the behaviour of travelling fires subject to different compartment boundary conditions.