Stochastic modeling of the flight of embers ejected from an ember dragon

Abstract

Spot-fire generation from embers blown ahead of a wildfire front is one of the leading causes of home destruction in wildland-urban interface (WUI) fires. It is, therefore, important to be able to model wind-driven ember flight accurately. This study presents the application of a stochastic debris flight model to this problem. The model embeds the uncertainty in flight conditions into the model by randomly perturbing the flight parameters (drag and lift forces) at each numerical integration time step. The stochastic flight model replicates the results of a series of ember flight tests run using the Victoria University ember dragon for both cubic and cylindrical model embers. Results show that the stochastic model produces very good predictions of the mean landing location of the embers tested. The model also provides reasonable estimates of the standard deviation and skewness of the landing location distribution in the direction of the initial launch for the cubic embers. The agreement with higher moment statistics is poorer for the cylindrical embers, though there is qualitative consistency between the experimental and model spatial distributions.