Duncan Sutherland

Physics-Based Simulations of Flow and Fire Development Downstream of a Canopy

Publisher: MDPI AG

Date: 28-06-2020

DOI: 10.3390/ATMOS11070683

Abstract: The behavior of a grassland fire propagating downstream of a forest canopy has been simulated numerically using the fully physics-based wildfire model FIRESTAR3D. This configuration reproduces quite accurately the situation encountered when a wildfire spreads from a forest to an open grassland, as can be the case in a fuel break or a clearing, or during a prescribed burning operation. One of the objectives of this study was to evaluate the impact of the presence of a canopy upstream of a grassfire, especially the modifications of the local wind conditions before and inside a clearing or a fuel break. The knowledge of this kind of information constitutes a major element in improving the safety conditions of forest managers and firefighters in charge of firefighting or prescribed burning operations in such configurations. Another objective was to study the behavior of the fire under realistic turbulent flow conditions, i.e., flow resulting from the interaction between an atmospheric boundary layer (ABL) with a surrounding canopy. Therefore, the study was ided into two phases. The first phase consisted of generating an ABL/canopy turbulent flow above a pine forest (10 m high, 200 m long) using periodic boundary conditions along the streamwise direction. Large Eddy Simulations (LES) were carried out for a sufficiently long time to achieve a quasi-fully developed turbulence. The second phase consisted of simulating the propagation of a surface fire through a grassland, bordered upstream by a forest section (having the same characteristics used for the first step), while imposing the turbulent flow obtained from the first step as a dynamic inlet condition to the domain. The simulations were carried out for a wind speed that ranged between 1 and 12 m/s these values have allowed the simulations to cover the two regimes of propagation of surfaces fires, namely plume-dominated and wind-driven fires.

A response to comments of Cruz et al. on: ‘Simulation study of grass fire using a physics-based model: striving towards numerical rigour and the effect of grass height on the rate of spread'

Publisher: CSIRO Publishing

Date: 2021

DOI: 10.1071/WF20091

Numerical study on effect of relative humidity (and fuel moisture) on modes of grassfire propagation

Publisher: Elsevier BV

Date: 10-2021

DOI: 10.1016/J.FIRESAF.2021.103422

Physics-Based Simulation of Heat Load on Structures for Improving Construction Standards for Bushfire Prone Areas

Publisher: Frontiers Media SA

Date: 28-06-2019

DOI: 10.3389/FMECH.2019.00035

Verification of a Lagrangian particle model for short-range firebrand transport

Publisher: Elsevier BV

Date: 07-2017

DOI: 10.1016/J.FIRESAF.2017.03.019

Modelling of tree fires and fires transitioning from the forest floor to the canopy with a physics-based model

Publisher: Elsevier BV

Date: 09-2020

DOI: 10.1016/J.MATCOM.2019.05.018

The effect of ignition protocol on grassfire development

Publisher: CSIRO Publishing

Date: 2020

DOI: 10.1071/WF19046

Abstract: The effect of ignition protocol on the development of grassfires is investigated using physics-based simulation. Simulation allows measurement of the forward rate of spread of a fire as a function of time at high temporal resolution. Two ignition protocols are considered: the inward ignition protocol, where the ignition proceeds in a straight line from the edges of the burnable fire plot to the centre of the plot and the outwards ignition protocol, where the ignition proceeds from the centre of the burnable fire plot to the edges of the plot. In addition to the two ignition protocols, the wind speed, time taken for the ignition to be completed and ignition line length are varied. The rate of spread (R) of the resultant fires is analysed. The outwards ignition protocol leads to an (approximately) monotonic increase in R, whereas the inward ignition protocol can lead to a peak in R before decreasing to the quasi-equilibrium R. The fires simulated here typically take 50m from the ignition line to develop a quasi-equilibrium R. The results suggest that a faster ignition is preferable to achieve a quasi-equilibrium R in the shortest distance from the ignition line.

A response to comments of Cruz et al. on: 'The effect of ignition protocol on the spread rate of grass fires'

Publisher: CSIRO Publishing

Date: 2020

DOI: 10.1071/WF20046

Kinetics of pyrolysis of litter materials from pine and eucalyptus forests

Publisher: Springer Science and Business Media LLC

Date: 14-06-2017

DOI: 10.1007/S10973-017-6512-0

The effect of slip length on vortex rebound from a rigid boundary

Publisher: AIP Publishing

Date: 09-2013

DOI: 10.1063/1.4821774

Abstract: The problem of a dipole incident normally on a rigid boundary, for moderate to large Reynolds numbers, has recently been treated numerically using a volume penalisation method by Nguyen van yen, Farge, and Schneider [Phys. Rev. Lett. 106, 184502 (2011)]. Their results indicate that energy dissipating structures persist in the inviscid limit. They found that the use of penalisation methods intrinsically introduces some slip at the boundary wall, where the slip approaches zero as the Reynolds number goes to infinity, so reducing to the no-slip case in this limit. We study the same problem, for both no-slip and partial slip cases, using compact differences on a Chebyshev grid in the direction normal to the wall and Fourier methods in the direction along the wall. We find that for the no-slip case there is no indication of the persistence of energy dissipating structures in the limit as viscosity approaches zero and that this also holds for any fixed slip length. However, when the slip length is taken to vary inversely with Reynolds number then the results of Nguyen van yen et al. are regained. It therefore appears that the prediction that energy dissipating structures persist in the inviscid limit follows from the two limits of wall slip length going to zero, and viscosity going to zero, not being treated independently in their use of the volume penalisation method.

Simulation study of grass fire using a physics-based model: striving towards numerical rigour and the effect of grass height on the rate of spread

Publisher: CSIRO Publishing

Date: 2018

DOI: 10.1071/WF17126

Abstract: Grid-independent rate of spread results from a physics-based simulation are presented. Previously, such a numerical benchmark has been elusive owing to computational restrictions. The grid-converged results are used to systematically construct correlations between the rate of spread (RoS) and both wind speed and grass height, separately. The RoS obtained from the physics-based model is found to be linear with wind speed in the parameter range considered. When wind speed is varied, the physics-based model predicts faster RoS than the Mk III and V (McArthur) models (Noble et al. 1980) but slower than the CSIRO model (Cheney et al. 1998). When the grass height is varied keeping the bulk density constant, the fire front changes from a boundary layer flame mode to plume flame mode as the grass height increases. Once the fires are in plume mode, a higher grass height results in a larger heat release rate of the fire but a slower RoS.

University Of New South Wales

Location: Australia

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University Of Sydney

Location: Australia

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Understanding The Origin And Development Of Extreme And Mega Bushfires

Start Date: 2021

End Date: 2024

Funder: Australian Research Council

Gravity Current Driven Smoke Dispersion In A Stratified Ambient

Start Date: 2021

End Date: 2024

Funder: Australian Research Council

Discovery Projects - Grant ID: DP210101965

Start Date: 06-2021

End Date: 12-2024

Amount: $250,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP210102540

Start Date: 08-2021

End Date: 08-2024

Amount: $590,000.00

Funder: Australian Research Council