Determination of water application rates required for communities to suppress post‐flashover informal settlement fires based on numerical modelling and experimental tests

Abstract

SummaryFires originating in informal settlements (ie, slums, ghettos, shantytowns, squatter camps) spread rapidly, due to the presence of densely packed, highly combustible dwellings, thereby making these communities inherently susceptible to large conflagrations. By the time, the fire brigades are notified and can get to the scene of the fire, the resulting conflagrations can be large. Thus, it is necessary to equip communities with the ability to combat smaller fires, although it is acknowledged that this is not ideal. Previous full‐scale testing and firefighter experience have shown that water application through ‘bucket brigades’ can be very effective at suppressing fires. In this article, a model is developed for approximately quantifying the amount of water, and discharge rate, that is, required for communities to suppress fires of various sizes using bucket brigades. This is done to answer the question: based on the water supply infrastructure in an area could a community put out post‐flashover fires of certain sizes? If this is not feasible, it would highlight the importance of communities having readily available pre‐filled water buckets at homes. The model presented is developed in fire dynamics simulator and is calibrated based on full‐scale experiments utilizing the bucket brigade technique. It is shown that standpipe discharge rates of 23 to 40 lpm are suitable for fire sizes of around 3.85 MW, based on a dwelling size of 2.4 x 3.6 x 2.4 m. This means that in communities with a single stand‐pipe (water supply point) with flow rates less than 23 lpm, that fires greater than 3.85 MW (as produced by a home of 2.4 x 3.6 m with a timber fuel load of 25 kg/m2) cannot be suppressed in time without resulting in substantial fire spread to adjacent dwellings.

Numerical Study on the Effect of Atmospheric Wind on the Fire Severity in Informal Settlements with Different Dwellings’ Wall Thermal Characteristics

“…The numerical simulations were carried out using the Fire Dynamics Simulator (FDS), a Computational Fluid Dynamics (CFD) simulation that has been utilized by various researchers to explore fire dynamics and fire spread [9, 11-14, 24, 26-30]. The model was built on a full-scale ISO 9705 room geometry, which accurately simulates an IS household and has been used by various writers [9,11,14,27,[31][32][33][34][35][36][37]. The house was subjected to varying wind speeds (1 m/s, 5 m/s, 10 m/s, 15 m/s, 20 m/s, and 25 m/s) and directions (side wind and back wind, relatively to the compartment opening placed at the front wall).Additionally, different compartment boundary characteristics (thermally-thin and thermally-thick) were considered.…”

“…Another important aspect that has been observed in IS dwellings are the leakages experienced at the wall-roof intersections, which occurs as a result of the poor construction and corrugated sheeting geometry (profile) [11]. The effect of leakages and ventilation conditions in informal settlement (both on a settlement and dwelling scale) fire dynamics was investigated by Cicione et al [12].…”