Effects of Leakage in Simulations of Positive Pressure Ventilation

The fire service uses a number of tactics to reduce hazards for fire-fighters and civilians within a structure on fire. One offensive fire-fighting tactic that has potential for rapidly improving or degrading conditions within the structure is ventilating the structure. Positive pressure ventilation is a tactic in which a fan is used to push hot products of combustion out of a burning structure. While a recent body of work has been produced on the effects of positive pressure ventilation in a number of fire systems, there is still widespread uncertainty on how the tactic affects the fire environment. Computational tools will play an important role in exploring the impact of positive pressure ventilation in various fire scenarios. In many simulations of structure fires, the impact of leakage on the evolution of the fire is not addressed. We find in this study that ad hoc models of leakage have significant impact on the evolution of the fire. Several ad hoc leakage models are proposed and these are studied in terms of their impact of the fire. We show that one particular leakage geometry is able to best model leakage effects in a series of fire simulations that are compared to experiments. Simple, first-order analysis is used to understand how these leakage flows affect the predictions.