A Numerical Study of the Relationship Between Compartment Fire Evolution and External Fire Exposure Conditions

ABSTRACT In densely populated urban areas, the spread of fire between buildings is a significant risk. Many urban spaces have evolved with a preference for quick and cheap construction in deference to fire safety and adherence to any applicable local building regulations. With the increasing use of combustible and flammable materials inside and on our buildings, exacerbating the potential for building‐to‐building fire spread, it is therefore necessary to re‐evaluate the threat to the built environment due to this scenario. In order to address this research gap, computational fluid dynamics is implemented as a tool to simulate the behaviour of a fire and to determine the spatial evolution of the external temperature and heat flux away from the burning compartment's external openings under varied fuel load, fire growth rate and ventilation modes. It is shown that these outputs are a function of the heat release inside of the compartment as well as the internal ventilation conditions, with internal doors being closed increasing the intensity and extent of external conditions. This gives insight into factors which could lead to subsequent secondary ignition away from the compartment of origin. We also show that for a given heat release rate, the criteria for window breakage and therefore the time at which window breakage occurs is irrelevant to the ultimate magnitude and extent of the external conditions. These reflect essential considerations, necessary for ignition criteria of novel/new material consideration in the context of building‐to‐building fire spread in high density housing stock.