CFD as a tool for examining fire spread mechanisms in informal settlements: faster flashover and deflected flames

2021 ◽  
Author(s):  
Samuel Stevens ◽  
Mohamed Beshir ◽  
David Rush
Keyword(s):  
Informal Settlements ◽  
Fire Spread

scholarly journals Determination of Critical Separation Distance Between Dwellings in Informal Settlements Fire

2021 ◽  
Author(s):  
Yu Wang ◽  
Lesley Gibson ◽  
Mohamed Beshir ◽  
David Rush
Keyword(s):  
Heat Flux ◽  
Informal Settlement ◽  
Informal Settlements ◽  
Fire Risk ◽  
Fire Spread ◽  
Separation Distance ◽  
Flame Length ◽  
Critical Distance ◽  
Fire Disaster ◽  
Critical Separation

AbstractApproximately one billion people across the globe are living in informal settlements with a large potential fire risk. Due to the high dwelling density, a single informal settlement dwelling fire may result in a very serious fire disaster leaving thousands of people homeless. In this work, a simple physics-based theoretical model was employed to assess the critical fire separation distance between dwellings. The heat flux and ejected flame length were obtained from a full-scale dwelling tests with ISO 9705 dimension (3.6 m × 2.4 m × 2.4 m) to estimate the radiation decay coefficient of the radiation heat flux away from the open door. The ignition potential of combustible materials in adjacent dwellings are analyzed based on the critical heat flux from cone calorimeter tests. To verify the critical distance in real informal settlement fire, a parallel method using aerial photography within geographic information systems (GIS), was employed to determine the critical separation distances in four real informal settlement fires of 2014–2015 in Masiphumelele, Cape Town, South Africa. The fire-spread distances were obtained as well through the real fires. The probabilistic analysis was conducted by Weibull distribution and logistic regression, and the corresponding separation distances were given with different fire spread probabilities. From the experiments with the assumption of no interventions and open doors and windows, it was established that the heat flux would decay from around 36 kW/m2 within a distance of 1.0 m to a value smaller than 5 kW/m2 at a distance of 4.0 m. Both experiments and GIS results agree well and suggest the ignition probabilities at distances of 1.0 m, 2.0 m and 3.0 m are 97%, 52% and 5% respectively. While wind is not explicitly considered in the work, it is implicit within the GIS analyses of fire spread risk, therefore, it is reasonable to say that there is a relatively low fire spread risk at distances greater than 3 m. The distance of 1.0 m in GIS is verified to well and conservatively predict the fire spread risk in the informal settlements.

scholarly journals 20 Dwelling Large-Scale Experiment of Fire Spread in Informal Settlements

2020 ◽  
Vol 56 (4) ◽  
pp. 1599-1620 ◽  
Author(s):  
N. de Koker ◽  
R. S. Walls ◽  
A. Cicione ◽  
Z. R. Sander ◽  
S. Löffel ◽  
...  
Keyword(s):  
Large Scale ◽  
Informal Settlements ◽  
Fire Spread ◽  
Scale Experiment

scholarly journals Experimental and Numerical Study for the Effect of Horizontal Openings on the External Plume and Potential Fire Spread in Informal Settlements

2021 ◽  
Vol 11 (5) ◽  
pp. 2380
Author(s):  
Mohamed Beshir ◽  
Karim Omar ◽  
Felipe Roman Centeno ◽  
Samuel Stevens ◽  
Lesley Gibson ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Heat Flux ◽  
Computational Fluid Dynamics ◽  
Radiative Heat ◽  
Numerical Study ◽  
Informal Settlement ◽  
Informal Settlements ◽  
Fire Spread ◽  
Heat Fluxes ◽  
Fuel Load

According to recent UN reports, it is estimated that more than one billion people live in informal settlements globally, exposing them to a large potential fire risk. In previous research, it was found that the main fire spread mechanism between dwellings is the external flaming (plume) and radiative heat fluxes from the vertical openings at the dwelling of origin to the surroundings. In this paper, an experimental and numerical study was conducted to quantify the effect of adding horizontal roof openings to the design of informal settlement dwellings to reduce the fire spread risk by decreasing the length of flames and radiation from the external plumes at the vertical openings. In total, 19 quarter scale ISO-9705 compartment fire experiments were conducted using an identical fuel load (80 MJ/m2) of polypropylene and were used to validate a physical computational fluid dynamics model for future studies. Five different total horizontal openings areas (0.0025, 0.01, 0.04, 0.09, and 0.16 m2) were investigated using two horizontal openings designs: (1) four square openings at the four corners of the compartment and (2) one slot cut at the middle of the compartment. It was found that adding horizontal openings decreased the average heat flux measured at the door by up to 65% and 69% for corner and slot cases, respectively. Heat flux reductions were achieved at opening areas as low as 0.01 m2 for slot cases, whereas reductions were only achieved at areas of at least 0.09 m2 for corner cases. The Computational Fluid Dynamics (CFD) model was validated using the experimental results. It successfully captured the main fire dynamics within the compartment in addition to the values of the external radiative heat flux. Further, a new empirical ventilation factor was generated to describe the flow field through both openings configurations which showed strong coupling with the inlet mass of fresh air to the compartment.

The influence of wind and the spatial layout of dwellings on fire spread in informal settlements in Cape Town

2022 ◽  
Vol 91 ◽  
pp. 101734
Author(s):  
Lesley Gibson ◽  
Antonio Cicione ◽  
Samuel Stevens ◽  
David Rush
Keyword(s):  
Cape Town ◽  
Informal Settlements ◽  
Fire Spread ◽  
Spatial Layout

Modelling the influence of wind on fire spread within informal settlements

2021 ◽  
Author(s):  
David Rush ◽  
Luoyi Gu ◽  
Alannah Trimble ◽  
Mohamed Beshir ◽  
Lesley Gibson
Keyword(s):  
Informal Settlements ◽  
Fire Spread
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