Abstract:
Façade fires are one of the most critical and increasingly frequent hazards in buildings. These
fires pose a great risk to the building occupants. The Grenfell Tower fire, which happened in
2017, killing 72 people, is one of the deadliest façade fire incidents. Events like these
emphasize the importance of studying the nature of façade fires. Façade fires can spread
quickly through the full height of the building. Also, these fires can spread into nearby
structures. Researchers have identified several factors that affect façade fire propagation. The
main factors include façade material, cavities, geometry of the building, and wind. The focus
of this study is the effect of wind on façade fire propagation. Building standards have set
requirements to ensure the fire safety of façades. A large-scale façade fire test is one of the
methods that building standards have used for this purpose. There are several large-scale façade
fire test types in different countries, and the nature of these tests varies significantly from one
another. One common theme in all those tests is that they do not consider the effect of wind.
Therefore, even though the façades are designed according to the building standards, there is
an unforeseen risk in fire situations when the wind is present. This study tries to address that
limitation by numerically modelling a large-scale façade fire test and assessing the effect of
wind. Fire Dynamic Simulator (FDS) was selected as the numerical tool. FDS is a
Computational Fluid Dynamics (CFD) software for fire-driven fluid flows. First, a validation
study was performed by numerically modelling a large-scale façade fire test that was conducted
in a fire test facility in Melbourne. The experimental setup was 18 m tall, and thermocouples
were placed at 10.5 m, 13.5 m and 16.5 m heights to record the temperatures. Wind speed and
direction were measured at a height of 10 m. The test specimen consisted of two façade
materials: an aluminium composite panel (ACP) with a combustible polyethylene core and a
completely non-combustible profiled aluminium panel. The ACP panels consisted of a 4 mm
polyethylene core sandwiched in between two 1 mm thick aluminium sheets. These materials
were simulated in the numerical model using the material properties gathered from literature
and product-specific data sheets. The total dimensions of the numerical domain were 22.4 m x
20.8 m x 19.2 m (length x width x height). This domain was large enough to account for the
whole test, the fire plume resulting from the combustion, and the turbulences due to wind.
Monin-Obukhov similarity theory was used to model the wind inside the numerical domain.
The thermocouple results were extracted from the numerical model, and they were validated
using the experimental results. The flame behaviour of the numerical model was compared
with that of the experiment for further validation. After the validation, the effect of wind was
examined through further numerical modelling. It has been shown that wind has a significant
impact on façade fire propagation. The façade fire spread decreases with increasing wind speed
when the wind direction is parallel to the main wall of the test specimen. Wind direction also
impacts fire propagation. Findings from this study highlight the importance of considering
wind in façade fire safety, especially in large-scale façade fire tests.