Coupled Fire-Atmosphere Simulation

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Biosphere/Hydrosphere/Land–Atmosphere Interactions".

Deadline for manuscript submissions: closed (15 October 2020) | Viewed by 28924

Special Issue Editors


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Guest Editor
School of Science, University of New South Wales Canberra, Canberra, BC 2610, Australia
Interests: bushfire; wildfire; fire weather; modelling; fire–atmosphere interaction
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Guest Editor
Institute for Sustainable Industries and Livable Cities, Victoria University, Melbourne, VIC 3030, Australia
Interests: computational fluid dynamics, enclosure fire dynamics; wildland fire modelling; fire detection and suppression; fire risk analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Atmosphere is dedicating this Special Issue to communicating the latest developments in coupled fire–atmosphere modelling. In the last few decades, considerable effort has been put into the design and implementation of models that enable consideration of the two-way interaction between fire and the atmosphere. These models have provided insights into the distinctly dynamic nature of wildfire propagation across a landscape and are continuing to contribute to leading edge wildfire science.

This Special Issue provides an opportunity for those involved in modelling the fire–atmosphere system across a range of scales—from fine-scale combustion dynamics to large pyroconvective events—to present their work in a dedicated volume. We therefore invite you to contribute articles to this Special Issue that highlight advances, new insights, technical issues and emerging research directions associated with existing and emerging coupled fire–atmosphere modelling frameworks. Contributions that describe idealised simulations as well as real-world case studies are welcome.

It is our intention that this Special Issue will help to promote discussion of important modelling issues and highlight synergies and linkages across the various modelling platforms and reasearch groups, which will lead to fruitful collaboration and progress in modelling the fire–atmosphere system at relevant scales.

Prof. Jason J. Sharples
Prof. Khalid Moinuddin
Guest Editors

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Keywords

  • Fire–atmosphere interaction 
  • Coupled fire–atmosphere model 
  • Dynamic fire behaviour 
  • Extreme fire 
  • Pyroconvection

Published Papers (10 papers)

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19 pages, 5832 KiB  
Article
The Role of Heat Flux in an Idealised Firebreak Built in Surface and Crown Fires
by Nazmul Khan and Khalid Moinuddin
Atmosphere 2021, 12(11), 1395; https://doi.org/10.3390/atmos12111395 - 25 Oct 2021
Cited by 5 | Viewed by 2158
Abstract
The disruptions to wildland fires, such as firebreaks, roads and rivers, can limit the spread of wildfire propagating through surface or crown fire. A large forest can be separated into different zones by carefully constructing firebreaks through modification of vegetation in firebreak regions. [...] Read more.
The disruptions to wildland fires, such as firebreaks, roads and rivers, can limit the spread of wildfire propagating through surface or crown fire. A large forest can be separated into different zones by carefully constructing firebreaks through modification of vegetation in firebreak regions. However, the wildland fire behaviour can be unpredictable due to the presence of either wind- or buoyancy-driven flow in the fire. In this study, we aim to test the efficacy of an idealised firebreak constructed by unburned vegetation. The physics-based large eddy simulation (LES) simulation is conducted using Wildland–urban interface Fire Dynamic Simulator (WFDS). We have carefully chosen different wind velocities with low to high values, 2.5~12.5 m/s, so the different fire behaviours can be studied. The behaviour of surface fire is studied by Australian grassland vegetation, while the crown fire is represented by placing cone-shaped trees with grass underneath. With varying velocity and vegetation, four values of firebreak widths (Lc), ranging from 5~20 m, is tested for successful break distance needed for the firebreak. For each failure or successful firebreak width, we have assessed the characteristics of fire intensity, mechanism of heat transfer, heat flux, and surface temperature. It was found that with the inclusion of forest trees, the heat release rate (HRR) increased substantially due to greater amount of fuel involved. The non-dimensional Byram’s convective number (NC) was calculated, which justifies simulated heat flux and fire characteristics. For each case, HRR, total heat fluxes, total preheat flux, total preheat radiation and convective heat flux, surface temperature and fire propagation mode are presented in the details. Some threshold heat flux was observed on the far side of the firebreak and further studies are needed to identify them conclusively. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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15 pages, 2597 KiB  
Article
A Simple Model for Wildland Fire Vortex–Sink Interactions
by Bryan Quaife and Kevin Speer
Atmosphere 2021, 12(8), 1014; https://doi.org/10.3390/atmos12081014 - 7 Aug 2021
Cited by 4 | Viewed by 2440
Abstract
A model is developed to explore fire–atmosphere interactions due to the convective sink and vorticity sources in a highly simplified and idealized form, in order to examine their effect on spread and the stability of various fire front geometries. The model is constructed [...] Read more.
A model is developed to explore fire–atmosphere interactions due to the convective sink and vorticity sources in a highly simplified and idealized form, in order to examine their effect on spread and the stability of various fire front geometries. The model is constructed in a cellular automata framework, is linear, and represents a background flow, convective sink, and vortices induced by the fire plume at every burning cell. We use standard techniques to solve the resulting Poisson equations with careful attention to the boundary conditions. A modified Bresenham algorithm is developed to represent convection. The three basic flow types—large-scale background flow, sink flow, and vortex circulation—interact in a complex fashion as the geometry of the fire evolves. Fire-generated vortex–sink interactions produce a range of fire behavior, including unsteady spread rate, lateral spreading, and dynamic fingering. In this simplified framework, pulsation is found associated with evolving fire-line width, a fire-front acceleration in junction fires, and the breakup of longer initial fire lines into multiple head fires. Fuel is very simply represented by a single burn time parameter. The model fuel is uniform yet patchiness occurs due to a dynamic interaction of diffusive and convective effects. The interplay of fire-induced wind and the geometry of the fire front depends also on the fuel burn time. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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22 pages, 10551 KiB  
Article
Multiscale Modeling of Convection and Pollutant Transport Associated with Volcanic Eruption and Lava Flow: Application to the April 2007 Eruption of the Piton de la Fournaise (Reunion Island)
by Jean-Baptiste Filippi, Jonathan Durand, Pierre Tulet and Soline Bielli
Atmosphere 2021, 12(4), 507; https://doi.org/10.3390/atmos12040507 - 17 Apr 2021
Cited by 4 | Viewed by 2392
Abstract
Volcanic eruptions can cause damage to land and people living nearby, generate high concentrations of toxic gases, and also create large plumes that limit observations and the performance of forecasting models that rely on these observations. This study investigates the use of micro- [...] Read more.
Volcanic eruptions can cause damage to land and people living nearby, generate high concentrations of toxic gases, and also create large plumes that limit observations and the performance of forecasting models that rely on these observations. This study investigates the use of micro- to meso-scale simulation to represent and predict the convection, transport, and deposit of volcanic pollutants. The case under study is the 2007 eruption of the Piton de la Fournaise, simulated using a high-resolution, coupled lava/atmospheric approach (derived from wildfire/atmosphere coupled code) to account for the strong, localized heat and gaseous fluxes occurring near the vent, over the lava flow, and at the lava–sea interface. Higher resolution requires fluxes over the lava flow to be explicitly simulated to account for the induced convection over the flow, local mixing, and dilution. Comparisons with air quality values at local stations show that the simulation is in good agreement with observations in terms of sulfur concentration and dynamics, and performs better than lower resolution simulation with parameterized surface fluxes. In particular, the explicit representation of the thermal flows associated with lava allows the associated thermal breezes to be represented. This local modification of the wind flow strongly impacts the organization of the volcanic convection (injection height) and the regional transport of the sulfur dioxide emitted at the vent. These results show that explicitly solving volcanic activity/atmosphere complex interactions provides realistic forecasts of induced pollution. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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24 pages, 3686 KiB  
Article
A Multi-Fidelity Framework for Wildland Fire Behavior Simulations over Complex Terrain
by Marcos Vanella, Kevin McGrattan, Randall McDermott, Glenn Forney, William Mell, Emanuele Gissi and Paolo Fiorucci
Atmosphere 2021, 12(2), 273; https://doi.org/10.3390/atmos12020273 - 18 Feb 2021
Cited by 13 | Viewed by 3281
Abstract
A method for the large-eddy simulation (LES) of wildfire spread over complex terrain is presented. In this scheme, a cut-cell immersed boundary method (CC-IBM) is used to render the complex terrain, defined by a tessellation, on a rectilinear Cartesian grid. Discretization of scalar [...] Read more.
A method for the large-eddy simulation (LES) of wildfire spread over complex terrain is presented. In this scheme, a cut-cell immersed boundary method (CC-IBM) is used to render the complex terrain, defined by a tessellation, on a rectilinear Cartesian grid. Discretization of scalar transport equations for chemical species is done via a finite volume scheme on cut-cells defined by the intersection of the terrain geometry and the Cartesian cells. Momentum transport and heat transfer close to the immersed terrain are handled using dynamic wall models and a direct forcing immersed boundary method. A new “open” convective inflow/outflow method for specifying atmospheric wind boundary conditions is presented. Additionally, three basic approaches have been explored to model fire spread: (1) Representing the vegetation as a collection of Lagrangian particles, (2) representing the vegetation as a semi-porous boundary, and (3) representing the fire spread using a level set method, in which the fire spreads as a function of terrain slope, vegetation type, and wind speed. Several test and validation cases are reported to demonstrate the capabilities of this novel wildfire simulation methodology. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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19 pages, 4518 KiB  
Article
Modeling Low Intensity Fires: Lessons Learned from 2012 RxCADRE
by Rodman R. Linn, Judith L. Winterkamp, James H. Furman, Brett Williams, J. Kevin Hiers, Alexandra Jonko, Joseph J. O’Brien, Kara M. Yedinak and Scott Goodrick
Atmosphere 2021, 12(2), 139; https://doi.org/10.3390/atmos12020139 - 22 Jan 2021
Cited by 13 | Viewed by 2712
Abstract
Coupled fire-atmosphere models are increasingly being used to study low-intensity fires, such as those that are used in prescribed fire applications. Thus, the need arises to evaluate these models for their ability to accurately represent fire spread in marginal burning conditions. In this [...] Read more.
Coupled fire-atmosphere models are increasingly being used to study low-intensity fires, such as those that are used in prescribed fire applications. Thus, the need arises to evaluate these models for their ability to accurately represent fire spread in marginal burning conditions. In this study, wind and fuel data collected during the Prescribed Fire Combustion and Atmospheric Dynamics Research Experiments (RxCADRE) fire campaign were used to generate initial and boundary conditions for coupled fire-atmosphere simulations. We present a novel method to obtain fuels representation at the model grid scale using a combination of imagery, machine learning, and field sampling. Several methods to generate wind input conditions for the model from eight different anemometer measurements are explored. We find a strong sensitivity of fire outcomes to wind inputs. This result highlights the critical need to include variable wind fields as inputs in modeling marginal fire conditions. This work highlights the complexities of comparing physics-based model results against observations, which are more acute in marginal burning conditions, where stronger sensitivities to local variability in wind and fuels drive fire outcomes. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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17 pages, 5405 KiB  
Article
LES Simulation of Wind-Driven Wildfire Interaction with Idealized Structures in the Wildland-Urban Interface
by Mohsen Ghaderi, Maryam Ghodrat and Jason J. Sharples
Atmosphere 2021, 12(1), 21; https://doi.org/10.3390/atmos12010021 - 25 Dec 2020
Cited by 13 | Viewed by 3676
Abstract
This paper presents a numerical investigation of the impact of a wind-driven surface fire, comparable to a large wildfire, on an obstacle located downstream of the fire source. The numerical modelling was conducted using FireFOAM, a coupled fire-atmosphere model underpinned by a large [...] Read more.
This paper presents a numerical investigation of the impact of a wind-driven surface fire, comparable to a large wildfire, on an obstacle located downstream of the fire source. The numerical modelling was conducted using FireFOAM, a coupled fire-atmosphere model underpinned by a large eddy simulation (LES) solver, which is based on the Eddy Dissipation Concept (EDC) combustion model and implemented in the OpenFOAM platform (an open source CFD tool). The numerical data were validated using the aerodynamic measurements of a full-scale building model in the absence of fire effects. The results highlighted the physical phenomena contributing to the fire spread pattern and its thermal impact on the building. In addition, frequency analysis of the surface temperature fluctuations ahead of the fire front showed that the presence of a building influences the growth and formation of buoyant instabilities, which directly affect the behaviour of the fire’s plume. The coupled fire-atmosphere modelling presented here constitutes a fundamental step towards better understanding the behaviour and potential impacts of large wind-driven wildland fires in wildland-urban interface (WUI) areas. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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30 pages, 4222 KiB  
Article
Pressure-Gradient Forcing Methods for Large-Eddy Simulations of Flows in the Lower Atmospheric Boundary Layer
by François Pimont, Jean-Luc Dupuy, Rodman R. Linn, Jeremy A. Sauer and Domingo Muñoz-Esparza
Atmosphere 2020, 11(12), 1343; https://doi.org/10.3390/atmos11121343 - 11 Dec 2020
Cited by 5 | Viewed by 2409
Abstract
Turbulent flows over forest canopies have been successfully modeled using Large-Eddy Simulations (LES). Simulated winds result from the balance between a simplified pressure gradient forcing (e.g., a constant pressure-gradient or a canonical Ekman balance) and the dissipation of momentum, due to vegetation drag. [...] Read more.
Turbulent flows over forest canopies have been successfully modeled using Large-Eddy Simulations (LES). Simulated winds result from the balance between a simplified pressure gradient forcing (e.g., a constant pressure-gradient or a canonical Ekman balance) and the dissipation of momentum, due to vegetation drag. Little attention has been paid to the impacts of these forcing methods on flow features, despite practical challenges and unrealistic features, such as establishing stationary velocity or streak locking. This study presents a technique for capturing the effects of a pressure-gradient force (PGF), associated with atmospheric patterns much larger than the computational domain for idealized simulations of near-surface phenomena. Four variants of this new PGF are compared to existing forcings, for turbulence statistics, spectra, and temporal averages of flow fields. Results demonstrate that most features of the turbulent flow are captured. The variants can either enable modelers to prescribe a wind speed and direction at a reference height close to the ground as required in wildfire simulations, and/or mitigate streaks locking by reproducing the stability of the Ekman balance. Conditions of use, benefits, and drawbacks are discussed. PGF approaches, therefore, provide a viable solution for precursor inflows, including for the specific domains used in fire simulations. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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17 pages, 4755 KiB  
Article
Performance Evaluation of an Operational Rapid Response Fire Spread Forecasting System in the Southeast Mediterranean (Greece)
by Theodore M. Giannaros, Konstantinos Lagouvardos and Vassiliki Kotroni
Atmosphere 2020, 11(11), 1264; https://doi.org/10.3390/atmos11111264 - 23 Nov 2020
Cited by 9 | Viewed by 3260
Abstract
The current work presents the operational implementation and evaluation of a rapid response fire spread forecasting system, named IRIS, that was developed to provide support to the tactical wildfire suppression activities of the Hellenic Fire Corps. The system was operationally employed during the [...] Read more.
The current work presents the operational implementation and evaluation of a rapid response fire spread forecasting system, named IRIS, that was developed to provide support to the tactical wildfire suppression activities of the Hellenic Fire Corps. The system was operationally employed during the 2019 fire season in Greece, providing on-demand wildfire spread predictions for 17 incidents. Satellite remote sensing data were employed for quantitatively assessing IRIS’s predictions for eight selected events. Our results suggest an overall satisfactory model performance. More importantly, this study demonstrates that, as coupled fire-atmosphere modeling becomes an increasingly popular approach, the respective models have great potential to support operational agencies and wildfire managers during the incident phase. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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20 pages, 9862 KiB  
Article
Physics-Based Simulations of Flow and Fire Development Downstream of a Canopy
by Gilbert Accary, Duncan Sutherland, Nicolas Frangieh, Khalid Moinuddin, Ibrahim Shamseddine, Sofiane Meradji and Dominique Morvan
Atmosphere 2020, 11(7), 683; https://doi.org/10.3390/atmos11070683 - 28 Jun 2020
Cited by 2 | Viewed by 3245
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 [...] Read more.
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 divided 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. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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16 pages, 231 KiB  
Commentary
Lessons Learned from Coupled Fire-Atmosphere Research and Implications for Operational Fire Prediction and Meteorological Products Provided by the Bureau of Meteorology to Australian Fire Agencies
by Mika Peace, Joseph Charney and John Bally
Atmosphere 2020, 11(12), 1380; https://doi.org/10.3390/atmos11121380 - 21 Dec 2020
Cited by 4 | Viewed by 2285
Abstract
Coupled fire-atmosphere models are simulators that integrate a fire component and an atmospheric component, with the objective of capturing interactions between the fire and atmosphere. As a fire releases energy in the combustion process, the surrounding atmosphere adjusts in response to the energy [...] Read more.
Coupled fire-atmosphere models are simulators that integrate a fire component and an atmospheric component, with the objective of capturing interactions between the fire and atmosphere. As a fire releases energy in the combustion process, the surrounding atmosphere adjusts in response to the energy fluxes; coupled fire-atmosphere (CFA) models aim to resolve the processes through which these adjustments occur. Several CFA models have been developed internationally, mostly by meteorological institutions and primarily for use as a research tool. Research studies have provided valuable insights into some of the atmospheric processes surrounding a fire. The potential to run CFA models in real time is currently limited due to the intensive computational requirements. In addition, there is a need for systematic verification to establish their accuracy and the appropriate circumstances for their use. The Bureau of Meteorology (the Bureau) is responsible for providing relevant and accurate meteorological information to Australian fire agencies to inform decisions for the protection of life and property and to support hazard management activities. The inclusion of temporally and spatially detailed meteorological fields that adjust in response to the energy released by a fire is seen as a component in developing fire prediction systems that capture some of the most impactful fire and weather behavior. The Bureau’s ten-year research and development plan includes a commitment to developing CFA models, with the objective of providing enhanced services to Australian fire agencies. This paper discusses the operational use of fire predictions and simulators, learnings from CFA models and potential future directions for the Bureau in using CFA models to support fire prediction activities. Full article
(This article belongs to the Special Issue Coupled Fire-Atmosphere Simulation)
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