WIND-DRIVEN FIREBRAND DYNAMICS IN A NEAR-FOREST RESIDENTIAL AREA: A CASE STUDY OF MAUI WILDFIRE
Date
2024
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Abstract
The Lahaina wildfire disaster that occurred in early August 2023 resulted in a devastatingloss of life and history with an unprecedented rapid propagation rate. To better understand the
rapid and unexpected movement of fires, the study aims to analyze the potential impact of winddriven
movement of firebrand particles on fire spread. These firebrand particles can be primary
or supplemental causes in the erratic and quick spread of fires throughout wild and urbanized
areas through fire spotting. The present research focuses on the propagation of firebrand particles
within urbanized areas of Lahaina during high wind events caused by Hurricane Dora. 3D building
structures affected by the fire were reconstructed using the RHINO 8 software. The reconstruction
incorporated public building outlines and heights found in ArcGIS Pro. The high wind conditions
(from Hurricane Dora) are applied to a CFD model constructed using OpenFOAM software with six
houses in Lahaina, Ka‘akepa Street. Assuming that each simulated firebrand particle was spherical
and had a uniform combustion rate, the drag, gravitational, and random forces are included in a
dynamics model programmed using MATLAB. The wind profiles calculated using OpenFOAM are
inputted into the firebrand dynamics program to include realistic convective drag forces.
The combination of the coupled Eulerian-Lagrangian simulations portrays the propagation of
firebrands in the direction of the fast wind events observed on the day of the wildfire. The results
show that these particles travel over non-flammable surfaces, such as roads and sidewalks, and land
on flammable structures, such as downwind neighboring. The OpenFOAM simulations calculated
wind magnitude data, which indicated that wind speed was lower along the streets and that the
buildings were aligned with them after contact. Higher elevations had more significant wind speed
magnitudes. The particles primarily propagated in the downwind wind direction. This propagation
highlighted the impact of high wind conditions on the spread of firebrand particles. The results
showed that fires could spread during these harsh conditions if flammable material existed downwind
and wind conditions remained constant. These results demonstrate the ability of firebrands to travel
quickly and spread fires during high wind events, which calls for changes to the materials used in
constructing structures and the removal of highly flammable invasive grasses found in abundance in
Lahaina. This change will help prevent future disasters from reoccurring. The research conducted
can be used as an additional resource to avoid fire disasters further here in Hawai‘i.
Description
Keywords
Civil engineering, Environmental engineering, Firebrand, High wind, Lahaina, OpenFOAM, Particle
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47 pages
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