Numerical Investigation of Bushfire-Wind Interaction and its Impact on Building Structure

Abstract

Presented in this paper are the results of a numerical study on bushfire, wind and structure interactions. The association of bushfires with wind has long been recognized. However, the mechanism of their interaction has not received due attention. In the current study a computational fluid dynamics package was used to reveal the enhancement of wind by fires at scales comparable to buildings and the impact on buildings. The study also revealed a pulsation movement of flames under the influence of free stream wind conditions. The predicted pressure coefficient distribution around a building under no-fire condition was compared with the experimental result measured by others. Reasonably good agreement was obtained before a fire was added to reveal the impact of the fire.KEYWORDS: CFD, modeling, pressure coefficient, pulsation, velocity, wildfires. NOMENCLATURE LISTINGnormalized power spectrum (energy fraction at given frequency) (s)

LES Simulation of Wind-Driven Wildfire Interaction with Idealized Structures in the Wildland-Urban Interface

“…Thus, grid B with a high resolution near the walls was finally selected for further study while grid A was sufficient for aerodynamic performance prediction. Comparison of the measured mean pressure coefficients calculated for three different grid resolutions with experimental data [31] and numerical results reported by He et al [30] and Castro & Robins [62]; The measurements were taken on the building centreline shown by the solid line of (0-1-2-3); Uref = 6 m/s (no-fire case).…”

“…The second experiment used the experimental investigation of Castro and Robins [62], who examined the flow around a surface-mounted cube in uniform, irrotational and sheared turbulent flows. The third benchmarking case involved the results of a numerical study on bushfires, wind and structure interactions by He et al [30], who predicted pressure coefficient distribution around a building under no-fire conditions and compared this with the experimental results measured by others [30].…”

“…A detailed numerical study based on a fully physical model (Fire Dynamic Simulator, or FDS) focusing on the effect of wind-driven fires on a building was first carried out by He et al [30]. The numerical model was validated in the absence of fire using mean pressure measurements made on the full-scale, cube-shaped Silsoe building [31].…”

Numerical Investigation of the Effect of Sloped Terrain on Wind-Driven Surface Fire and Its Impact on Idealized Structures

“…One important aspect of wildfire research is directed towards the analysis of thermal and aerodynamic impacts of fire-enhanced wind on building structures in urban environments. The lack of enough research in analyzing the impact of wildfire on wind and buildings with mesh sizes smaller than the boundary layer thickness can be seen in the work of He and his co-authors [27]. Richards et al [28] reported an experimental and numerical investigation on the mean pressure of cube-shaped building and reported an important sets of data on the aerodynamic behavior of a building in the wind flow.…”

Existing Improvements in Simulation of Fire–Wind Interaction and Its Effects on Structures

“…The coupling of computational wind engineering and fire dynamics is introduced by considering the wind speed which is an essential parameter in modelling wildfire propagation. Numerical analysis performed by He et al [52] showed that the interaction between bushfire and wind generates a powerful local impact at areas closer to the ground or even at scales equivalent to the sizes of buildings. The buoyancy flux and mixed momentum can significantly distort the velocity profile of the wind such that the velocity of the wind near the ground is increased by over 50 percent at a given distance downstream of a moderate fire front.…”