PHOENIX RapidFire 4.0's Convective Plume Model

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Fire Behaviour
TitlePHOENIX RapidFire 4.0's Convective Plume Model
Publication TypeReport
Year of Publication2012
AuthorsChong, D, Tolhurst, KG, Duff, TJ
Date Published12/2012
AbstractBushfires are a 3-dimensional phenomenon with significant interaction between the surface and the atmosphere. Complex coupled fire-atmosphere models have been produced and give amazingly realistic results, however the computational complexity means that they take many times real-time to run, even on super computers, and are therefore restricted to small areas and short periods of time. PHOENIX RapidFire is primarily a 2-dimensional fire model and only takes a few minutes to run fires in excess of 100,000 ha. This report describes how PHOENIX RapidFire has been developed to include elements of plume development and ember transport resulting in spot fires. This was done to try and capture some of the important 3-dimensional aspects of bushfires without large computational overheads. Development of the plume rise and spotting components of PHOENIX has been done with the knowledge of some of the key thermodynamic processes, but a number of assumptions have been made. Validation of the plume rise and spotting model is difficult because there are no detailed observations recorded for the plume, embers, spotfires and upper-level winds. Ground-based weather radar data was found to be a useful validation dataset for the plume model. The plume model in PHOENIX was calibrated against weather radar data recorded on Black Saturday, 2009. Early indications are that there has been a significant improvement in the simulation of the Black Saturday fires with the incorporation of the plume and spotting models. Further testing will be required to fully understand the limitations of the model.