A numerical investigation of the interplay between fireline length, geometry, and rate of spread

Canfield, Jesse M.; Linn, Rodman R.; Sauer, Jeremy A.; Finney, Mark A.; Forthofer, Jason

doi:10.1016/j.agrformet.2014.01.007

Cited by 39 publications

(43 citation statements)

References 33 publications

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“…Interestingly, this underprediction of

| \nabla φ |

results on a bow‐shaped fire perimeter. Similar type of fire topology has been found in previous field campaigns and numerical modeling efforts (e.g., Canfield et al, ; Cheney et al, ; Clark et al, ; Linn & Cunningham, ). While in nature this is a physically plausible fire shape, it is solely induced by numerical errors in this particular case, since the fire‐atmosphere feedbacks responsible for that process where not included in our uncoupled simulations in order to be able to isolate the errors originating from the level‐set algorithm.…”

Section: Fire Spread Under a Uniform Velocity Fieldsupporting

confidence: 78%

An Accurate Fire‐Spread Algorithm in the Weather Research and Forecasting Model Using the Level‐Set Method

Muñoz‐Esparza

Kosović

Jiménez

et al. 2018

J Adv Model Earth Syst

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The level‐set method is typically used to track and propagate the fire perimeter in wildland fire models. Herein, a high‐order level‐set method using fifth‐order WENO scheme for the discretization of spatial derivatives and third‐order explicit Runge‐Kutta temporal integration is implemented within the Weather Research and Forecasting model wildland fire physics package, WRF‐Fire. The algorithm includes solution of an additional partial differential equation for level‐set reinitialization. The accuracy of the fire‐front shape and rate of spread in uncoupled simulations is systematically analyzed. It is demonstrated that the common implementation used by level‐set‐based wildfire models yields to rate‐of‐spread errors in the range 10–35% for typical grid sizes (Δ = 12.5–100 m) and considerably underestimates fire area. Moreover, the amplitude of fire‐front gradients in the presence of explicitly resolved turbulence features is systematically underestimated. In contrast, the new WRF‐Fire algorithm results in rate‐of‐spread errors that are lower than 1% and that become nearly grid independent. Also, the underestimation of fire area at the sharp transition between the fire front and the lateral flanks is found to be reduced by a factor of ≈7. A hybrid‐order level‐set method with locally reduced artificial viscosity is proposed, which substantially alleviates the computational cost associated with high‐order discretizations while preserving accuracy. Simulations of the Last Chance wildfire demonstrate additional benefits of high‐order accurate level‐set algorithms when dealing with complex fuel heterogeneities, enabling propagation across narrow fuel gaps and more accurate fire backing over the lee side of no fuel clusters.

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“…Interestingly, this underprediction of

| \nabla φ |

Section: Fire Spread Under a Uniform Velocity Fieldsupporting

confidence: 78%

An Accurate Fire‐Spread Algorithm in the Weather Research and Forecasting Model Using the Level‐Set Method

Muñoz‐Esparza

Kosović

Jiménez

et al. 2018

J Adv Model Earth Syst

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“…The HIGRAD model (Fierro & Reisner, ; Margolin & Reisner, ; Reisner & Jeffery, ) solves the compressible Navier‐Stokes equations, and when linked to various physics packages such as FIRETEC, a physics‐based fire dynamics model (Canfield et al, ; Linn, ; Linn et al, , ; Linn & Cunningham, ; Pimont et al, ), HIGRAD‐FIRETEC can be used to study the evolution and spread of fire and its two‐way interaction with atmospheric dynamics. The HIGRAD‐FIRETEC modeling system has been used to simulate a wide variety of fire behavior over the past 20 years, from slow‐moving grass fires to fast‐moving mass fires in an urban environment.…”

Section: Model Descriptionsmentioning

confidence: 99%

Climate Impact of a Regional Nuclear Weapons Exchange: An Improved Assessment Based On Detailed Source Calculations

et al. 2018

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We present a multiscale study examining the impact of a regional exchange of nuclear weapons on global climate. Our models investigate multiple phases of the effects of nuclear weapons usage, including growth and rise of the nuclear fireball, ignition and spread of the induced firestorm, and comprehensive Earth system modeling of the oceans, land, ice, and atmosphere. This study follows from the scenario originally envisioned by Robock, Oman, Stenchikov, et al. (2007, https://doi.org/10.5194/acp-7-2003-2007), based on the analysis of Toon et al. (2007, https://doi.org/10.5194/acp-7-1973-2007), which assumes a regional exchange between India and Pakistan of fifty 15 kt weapons detonated by each side. We expand this scenario by modeling the processes that lead to production of black carbon, in order to refine the black carbon forcing estimates of these previous studies. When the Earth system model is initiated with 5 × 109 kg of black carbon in the upper troposphere (approximately from 9 to 13 km), the impact on climate variables such as global temperature and precipitation in our simulations is similar to that predicted by previously published work. However, while our thorough simulations of the firestorm produce about 3.7 × 109 kg of black carbon, we find that the vast majority of the black carbon never reaches an altitude above weather systems (approximately 12 km). Therefore, our Earth system model simulations conducted with model‐informed atmospheric distributions of black carbon produce significantly lower global climatic impacts than assessed in prior studies, as the carbon at lower altitudes is more quickly removed from the atmosphere. In addition, our model ensembles indicate that statistically significant effects on global surface temperatures are limited to the first 5 years and are much smaller in magnitude than those shown in earlier works. None of the simulations produced a nuclear winter effect. We find that the effects on global surface temperatures are not uniform and are concentrated primarily around the highest arctic latitudes, dramatically reducing the global impact on human health and agriculture compared with that reported by earlier studies. Our analysis demonstrates that the probability of significant global cooling from a limited exchange scenario as envisioned in previous studies is highly unlikely, a conclusion supported by examination of natural analogs, such as large forest fires and volcanic eruptions.

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“…1E) beneath flame peaks. These were visualized as isosurfaces of helicity in the vicinity of the fireline during numerical simulations of wildfire spread (32) (Figs. 1G and 2).…”

Section: Significancementioning

confidence: 99%

Role of buoyant flame dynamics in wildfire spread

Finney

Cohen

Forthofer

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

289

166

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Large wildfires of increasing frequency and severity threaten local populations and natural resources and contribute carbon emissions into the earth-climate system. Although wildfires have been researched and modeled for decades, no verifiable physical theory of spread is available to form the basis for the precise predictions needed to manage fires more effectively and reduce their environmental, economic, ecological, and climate impacts. Here, we report new experiments conducted at multiple scales that appear to reveal how wildfire spread derives from the tight coupling between flame dynamics induced by buoyancy and fine-particle response to convection. Convective cooling of the fine-sized fuel particles in wildland vegetation is observed to efficiently offset heating by thermal radiation until convective heating by contact with flames and hot gasses occurs. The structure and intermittency of flames that ignite fuel particles were found to correlate with instabilities induced by the strong buoyancy of the flame zone itself. Discovery that ignition in wildfires is critically dependent on nonsteady flame convection governed by buoyant and inertial interaction advances both theory and the physical basis for practical modeling.wildfires | buoyant instability | flame spread | convective heating

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A numerical investigation of the interplay between fireline length, geometry, and rate of spread

Cited by 39 publications

References 33 publications

An Accurate Fire‐Spread Algorithm in the Weather Research and Forecasting Model Using the Level‐Set Method

An Accurate Fire‐Spread Algorithm in the Weather Research and Forecasting Model Using the Level‐Set Method

Climate Impact of a Regional Nuclear Weapons Exchange: An Improved Assessment Based On Detailed Source Calculations

Role of buoyant flame dynamics in wildfire spread

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