Date of Award

August 2021

Document Type


Degree Name

Doctor of Philosophy (PhD)


Civil Engineering

Committee Member

Nigel B. Kaye

Committee Member

Abdul A. Khan

Committee Member

Weichiang Pang

Committee Member

M. Z. Z. Naser


Spot fire due to the ember accumulation is considered as the major cause of Wildland Urban Interface (WUI) structure ignition during wildfires. This dissertation develops techniques to investigate the regions on the roof top of a series of buildings which are likely to see the ember build up during an ember storm as well as study the accumulation rate of ember on the roofs. The results from experiments suggested that the vulnerable roof regions where embers have a significant chance of accumulated after landing are highly correlated to the aerodynamic forces on the roof. To be specific, the regions with the high dynamic force are where embers will not buildup after landing. Regarding the ember accumulation experiments, the mass of embers obtained on a single isolated building is highly sensitive to the wind direction, wind velocity and the shape of building including number and the direction of internal corners. In addition, the results of ember accumulation on the roof of building in a community layout show that with the normal grid layout community increasing the number of buildings upstream with a consistent of spacing between building generally results in a decrease in the mass of accumulated ember due to the appearance of the skimming flow induced by the upstream buildings. Whereas the upstream buildings in the staggered community layout might lead to the wake effect which in turn results in the larger ember accumulation mass with the case of upstream building rows of 2. For other cases of building rows of 3 and 4, the staggered layout also sees the reduction in the accumulated embers in comparison with the case of no surrounding buildings. Finally, the presence of the surrounding buildings in both layouts also affects the flow separation at the target building with less variation of dynamic force on the roof, resulting on the less variation of the amount of obtained ember for the same testing case.



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