Exploring fire dynamics of travelling fires in large open compartments with CFD

The evolution of fire conditions in large open compartments is studied by means of a CFD-based “numerical simulator” coupled with a multi-component pyrolysis model, implemented in FDS. A systematic parametric study is reported, based around a pair of full-scale fire experiments with uniform wood crib fuel beds, i.e. TRAFIR-Ulster tests 1 and 2, for which validation has previously been reported. The three parametric variants for each case essentially maintain the total areas of the vertical openings while redistributing their locations in the compartment walls to study their influence on fire spread and the associated fire dynamics. The fire evolution is found to be quite strongly influenced by the details of the compartment geometry, to an extent which exceeds the differences observed when only the level of confinement was changed, i.e. between the well-ventilated regime of Test 1 (inverse-opening-factor, ) and the transitional regime of Test 2 ( ). The analysis indicates that neither opening factor nor smoke layer height alone provides a reliable predictor of fire spread behaviours. These findings highlight the need to consider variations in fire severities beyond those which can be determined with simplified methods which recognise only the extent of potential opening areas rather than their arrangement. • Fire dynamics of travelling fires strongly influenced by compartment geometry • Differences arising from change of opening location exceed those of opening factors • Experimental findings extended by means of validated CFD-based “numerical simulator”