Search

Background. Climate change has increased the occurrence of fire-prone weather and extreme weather events in Europe. Improving resilience of forests to reduce fire hazard has become an imperative challenge to tackle. Aims. This study aims to incorporate extreme fire events from future climate projections in developing forest planning and land management scenarios, evaluating fire risk mitigation potential. Methods. Using the wildfire--atmosphere coupled modelling system WRF-SFIRE, land management scenarios for the Lombada Forest Intervention Region (ILMA) in northeast Portugal were assessed under a business-as-usual future climate scenario. The Fire Weather Index (FWI) was used as a predictor of fire danger to select two fire events. Results. Agricultural areas can function as barrier for wildfire conditions under cooler weather. Management of the existing pine forest yielded a reduction in fire spread speed and intensity, namely in lower wind speed regimes, significantly improving suppressive capabilities. Conclusions. Fuel treatment of maritime pine performed best in reducing fire spread rate, intensity and improving suppression capability. Replacing agricultural areas with oak-based land cover can promote higher fire intensity and spread rates in the younger stanges or if left unmanaged. Implications. This framework can be used to provide additional tools for forest management across different landscapes reducing fire hazard and vulnerability and improving forest resilience, under climate change. [ABSTRACT FROM AUTHOR]

In the Mediterranean basin, coniferous reforestation mainly comprises forest stands highly susceptible to fires. When silvicultural treatments have not been performed for decades after plantation, these stands often exhibit high vertical and horizontal tree density, along with a significant occurrence of lying and standing deadwood, thereby increasing the fuel load. On average, these pine forests are characterized by high values of above-ground biomass, ranging from 175 to 254 Mg ha−1 for the younger and the older ones, respectively. The theoretical heat energy produced per surface unit, in the case of the total combustion of the above-ground biomass, is also high, varying from 300 to 450 MJ ha−1 depending on the stage of stand development. In this study, we demonstrated the importance of silvicultural interventions in reducing the pyrological potential in pine reforested stands located in southern Italy, also giving attention to the water savings needed during extinction phases. In detail, we applied a preliminary mathematical reaction-diffusion model aimed at predicting the development of forest fires. The model was applied using data obtained through the estimation of the pyrological potential in terms of heat energy produced per surface unit (1 hectare) and the variation in the critical surface intensity. We verified that, when silvicultural interventions are applied, they induce a reduction of heat energy ranging between 17 and 21%, while the extinguishing water saved ranges between 600 and 1000 Mg ha−1. Moreover, when the silvicultural interventions are implemented, the probability of the transition from surface fire to crown fire can be reduced by up to 31%. The most effective results on fire risk mitigation are mainly obtained when thinning aimed at reducing canopy and tree density is carried out in the younger phases of the reforested pine stands. [ABSTRACT FROM AUTHOR]

Basic principles for a fire‐safe application of green façades on multi‐storey buildings. Green façades are in vogue. Fire spread along the façade is generally one of the most critical fire scenarios worldwide, and plants are additional combustible materials. The influence of green façades on fire propagation along the façade should therefore not be neglected. However, little research is available on this topic. The FireSafeGreen research project aims to change this. The main factor influencing the fire behaviour of plants is the moisture content. The plant species itself plays a subordinate role in terms of fire behaviour. A combination of wooden and green façade does not lead to an ignition of the wooden façade under consideration of some boundary conditions. In principle, appropriate care and maintenance are the key factors for fire‐safe green façades. [ABSTRACT FROM AUTHOR]

The object of this study is the process of fire propagation through the surface of external wall structures with facade thermal insulation. The paper examines the influence of facade parameters and the width of a fire-proof eaves on preventing the spread of fire by external vertical structures using the example of a residential building. With the use of FDS modeling, the relationships between the parameters of external enclosing structures and the fire-proof eaves on the processes of limiting the spread of fire were investigated. The influence of the minimum parameters of the height of the inter-floor windowsill in the absence of a fire-proof eaves on the spread of fire was determined. The dependence of temperature change near the surface of the facade on the width of the fire-proof eaves and the height of the window between floors was established. Based on a series of simulated experiments, it was established that with a height of 1.0 m between floors and the absence of a fire-proof eaves, the critical temperature value is 250 °C. This value corresponds to the destruction temperature of a standard metal-plastic window structure. For the case when the wall height is 1.0 m, and the width of the fire-proof eaves is 0.75 m, the temperature value is 180 °C. That is, the safety condition of 250 °C is met. Based on the research, a dependence was found on the criterion of not exceeding the critical temperature of 250 °C at the level of 1.4 m of the facade of the building floor located above the fire floor. The criterion holds when the width of a fire-proof eaves is at least 0.4 m and the height of the window partition is 1.0 m, as well as when the width of the eaves is 0.5 m, and the height of the window partition is 0.6 m. It was established that the height of a window interfloor partition has a smaller effect than the width of the fire-proof eaves that separates the floors that are located above. [ABSTRACT FROM AUTHOR]

Modeling and understanding of underground coal fire is of significance for green-and-safe mining of coal resources in China. Two issues remain unsolved in forward-propagation models of underground coal smoldering fires: one-step coal oxidation has been too simple so that endothermic reactions such as water evaporation and pyrolysis that have important influence on smoldering propagation of underground coal fires have been not considered; and models have not been validated via experimental data. In this work, a three-step chemical reaction scheme including water evaporation, coal pyrolysis, and char oxidation was employed and mathematic model in terms of forward propagation of underground coal smoldering fires was established. The theoretical model was numerically calculated using COMSOL Multiphysics finite element software. The theoretical model was numerically calculated using COMSOL Multiphysics finite element software, and the forward smoldering spread experiment of underground coal fire driven by thermal buoyancy under different ground crack permeability conditions was carried out. Comparison experiment and numerical calculation were carried out. Results show that the proposed model not only owns good capability to predict the peak temperature and velocity of smoldering propagation of underground coal fire, but also can inversely plot multiple step chemical reactions as well as spatiotemporal evolutions of oxygen and solid species mass fractions. In addition, the controlling mechanism of smoldering propagation of underground coal fires was further revealed.

Globalization impacts directly pollution, and one of the side effects is the increasing number of forest fires and their fast propagation. To reduce this phenomenon, several studies have tried to model fire propagation and find an adequate method to predict (or follow) this spread to stop it. However, to the best of our knowledge, most of the developed works do not use an adaptive exploration strategy to follow the fire evolution. Instead, they are mainly focused on observing the evolution and trying to find an adequate spread model to predict fire behavior. Due to the lack of all the exact parameters to predict the fire spread, in this paper, we propose a new exploration strategy based on reinforcement learning using an Unmanned Aerial Vehicle (UAV). The learned exploration strategy is able to predict and follow the fire propagation. To follow the generated waypoints by the exploration strategy, we develop a new robust controller, which can be embedded in a UAV. All these modules are encapsulated and interact with each other using a synchronized architecture. To prove the efficiency of our proposal, we present the obtained results on several simulated forest fire scenarios and compare them with other approaches. Then, We validate our entire architecture and show its efficiency using software in the loop environment using the Robot Operating System (ROS). [ABSTRACT FROM AUTHOR]

Background. Wildfires are becoming more severe, so we need improved tools to predict them over a wide range of conditions and scales. One approach towards this goal entails the use of coupled fire/atmosphere modelling tools. Although significant progress has been made in advancing their physical fidelity, existing tools have not taken full advantage of emerging programming paradigms and computing architectures to enable high-resolution wildfire simulations. Aims. The aim of this study was to present a new framework that enables landscapescale wildfire simulations with physical representation of combustion at an affordable cost. Methods. We developed a coupled fire/atmosphere simulation framework using TensorFlow, which enables efficient and scalable computations on Tensor Processing Units. Key results. Simulation results for a prescribed fire were compared with experimental data. Predicted fire behavior and statistical analysis for fire spread rate, scar area, and intermittency showed overall reasonable agreement. Scalability analysis was performed, showing close to linear scaling. Conclusions. While mesh refinement was shown to have less impact on global quantities, such as fire scar area and spread rate, it benefits predictions of intermittent fire behavior, buoyancy-driven dynamics, and small-scale turbulent motion. Implications. This new simulation framework is efficient in capturing both global quantities and unsteady dynamics of wildfires at high spatial resolutions. [ABSTRACT FROM AUTHOR]

Forest fires are becoming a more significant problem in Central Europe, but their danger is not as high as that in Southern Europe. The exception, however, is forest fires occurring in disturbed areas (windthrow and bark beetle outbreak areas), which are comparable in severity and danger to the most serious forest fires. In this study, we describe the current situation in Central European countries in terms of fire protection for disturbed areas in managed forests and forest stands left to spontaneously develop (secondary succession). If a country has regulations and strategies in this area, they are often only published in the local language. In this review, we combine information from all Central European countries and summarize it in a unified international language, provide an opportunity for local authorities to express their own experiences, and integrate data from worldwide scientific research. Thus, this paper may be considered a universal guide for managing fire protection and preparedness in disturbed areas and can serve as a reference for the establishment of strict legislative rules at the state level. These laws must be obligatory for all stakeholders in individual countries. The motivation for this study was two large forest fires in an area left to spontaneously develop in the Bohemian Switzerland National Park in the Czech Republic and Harz Mountains in Germany in the summer of 2022. These incidents revealed that fire prevention legislation was inadequate or nonexistent in these areas. The strategy of the European Union is to increase the size of protected areas and spontaneous development areas. Therefore, we consider it necessary to provide governments with relevant information on this topic to create conditions for better management of these destructive events. [ABSTRACT FROM AUTHOR]

Copyright of Ciência Florestal (01039954) is the property of Ciencia Florestal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fire safety is one of the major concerns in the public transport and thus passenger trains in the UK seek continuous improvement in passenger safety and comfort. In order to combat fire, there is a legal requirement in most countries across the global to install a fire suppression system within passenger railroad cars. In the event of fire, the thermal sensors trigger high pressure flow of hydrant through nozzles into the railroad car, thus supressing the fire. The efficient design of fire suppression system is highly dependent on the operational parameters of the system. The published literature, although abundant in investigating the flow characteristics through nozzles, severely lacks in conjugating this with fire suppression. Thus, in the present study, extensive parametric investigations have been carried out on the operational and design parameters of a conventional fire suppression system using an integrated approach i.e., hydrant flow and combustion. Advanced numerical techniques have been employed to evaluate the hydrodynamic characteristics of the fire suppression system based on the size of droplets of the hydrant from exiting the nozzles and the flow rate of the hydrant. The effects of these parameters on the temperature and the concentration of soot particles within the passenger railroad car have been evaluated. The results show that smaller sized hydrant droplets (250um) are more effective in supressing the fire in enclosures compared to larger droplets (750um), while higher flow rates tend to supress the fire more efficiently. It is envisaged that the results obtained in the present study will help in developing more efficient fire suppression systems for passenger railroad cars. [ABSTRACT FROM AUTHOR]

A stochastic model motivated by the Lagrangian transported probability density function method for turbulent reacting flows and the cellular automata approach for forest fires was put together to simulate propagation of fires in terrains with inhomogeneous composition. In contrast to the usual cellular automata models for fires where the probability of ignition is prescribed, here the ignition of cells is determined by a random walk that mimics turbulent convection and diffusion of the hot gases and firebrands from upwind and neighbouring fire fronts. Radiation is also included. The model is aimed at speed of computation while approximating the key physics through only a few terrain-related inputs and tunable parameters representing fire intensity, hot gas and ember decay timescales, cell ignition delay and local turbulence. These parameters were calibrated against controlled fire experiments and the model was then used to give reasonable predictions for fires of increasing complexity. The presented framework allows improvements for more accurate representation of the flammable material characteristics, fire-induced flow modifications, and most other phenomena present in fires, hence providing an extendable and simple yet physically-realistic novel modelling approach. [ABSTRACT FROM AUTHOR]

A large amount of storage may cause large-scale fire or explosion accidents due to the potential fire risk of lithium-ion batteries, which poses a great threat to the safety of personnel and property. In this study, the fire model of an individual cell is established according to the experimental data and the relevant parameters of thermal runaway simulation of large capacity battery are determined. The battery pack model is established according to the real setting of a warehouse. The fire characteristics of the battery pack spreading around in the warehouse environment are studied. The results show that the fire of lithium-ion batteries is preferentially diffused to the upper battery pack in the warehouse environment, and spread to the upper battery pack 19 s after the initial battery thermal runaway. The fire propagation of the horizontal battery pack is greatly affected by the distance. The farther the battery string is from the thermal runaway battery, the later the fire propagation battery string occurs. Furthermore, the role and effect of battery pack spacing, fire warning and automatic sprinkler system in fire are provided, so as to carry out better research on the storage safety of lithium-ion battery warehouses. [ABSTRACT FROM AUTHOR]

The interaction of wind and fire on a sloped terrain is always complex owing to the mechanisms of heat transfer and flame dynamics. Heating of unburned vegetation by attached flames may increase the rate of spread. The relative intensities of convective and radiative heat fluxes may change fire behaviour significantly. This paper presents a detailed analysis of flame dynamics, mode of fire propagation and surface radiative and convective heat fluxes on sloped terrain at various wind speeds using physics-based simulations. It was found that with increasing slope angles and wind velocity, the plume inclines more towards the ground and becomes elongated in upslope cases, whereas in downslope cases, the plume rises from the ground earlier. For higher wind velocities, the flame and near-surface flame dynamics appear to show rising, even though the plume is attached. The flame contour results indicate that the near-surface flame dynamics are difficult to characterise using Byram's number. A power-law correlation was observed between the simulated flame lengths and fireline intensities. The convective heat fluxes are more relevant for wind-driven fire propagation and greater upslopes, whereas both fluxes are equally significant for lower driving wind velocities compared with higher wind velocities. A physics-based study of grassfire behaviour over flat and sloped (upslope and downslope) terrain at field scale with varying wind velocities is presented. The flame dynamics, mode of fire propagation and surface radiative and convective heat fluxes are analysed. [ABSTRACT FROM AUTHOR]

Summary: The serious fire incident at Grenfell Tower in London, involving a combustible façade system that was installed as part of a major refurbishment of the building, has raised concerns regarding the fire risk that these systems pose. The fire spread over the façade of the Tower was previously numerically modelled and this model was validated by comparison with observational data. This model was used to determine the fire behavior of the façade and the fire's propagation into apartments through windows. In the present paper, impact models are used to evaluate tenability conditions inside the Tower, especially for the apartments in the first corner of the Tower that caught fire. The source of toxic effluents includes the components used in the refurbishment of the façade and the apartment furniture. Different hypotheses of gas yields are tested to assess variability and unknowns in the burning conditions. An extensive literature review was conducted to investigate the toxic yields to be considered in the simulations. Tenability conditions are assessed for each apartment during the fire spread over the façade. This leads to the quantification of the thermal and toxic environment inside the apartments. Two different models are tested for thermal and toxic threats, and the influence of the insulation material used in the façade is investigated. The results showed that the same conclusion can be made regardless of the input data for toxicity and the model used, within the limits of the studied dataset and conditions. Fires from the apartments quickly drive tenability conditions, independently of the dataset and model used, and even if mineral wool is used instead of poly‐isocyanurate as façade insulant. [ABSTRACT FROM AUTHOR]

Summary: The recent dramatic events at Grenfell Tower in London involving a combustible façade system have raised concerns regarding the fire risk that these systems pose. The spread of fire over the façade of the Tower was previously modelled numerically and the results of this modelling were validated by comparison with observations of the real fire. This model was used to determine the fire behaviour of the façade and the propagation of the façade fire into the apartments through windows. The modelling used an impact model according to ISO 13571 and included fire loads from the façade and, when relevant, from apartment contents. Tenability levels inside the apartments were quantified by an analysis of the toxic and thermal conditions due to the combustion of the façade materials and the apartment contents. In the present paper, the conditions inside the lobbies and stairs of the Tower are investigated, building on the previous analysis of the apartments. This allows an understanding of the evolution of toxic and thermal conditions whilst the fire spread, and their impact on egress during the fire event. [ABSTRACT FROM AUTHOR]

Forest fires are becoming a more significant problem in Central Europe, but their danger is not as high as that in Southern Europe. The exception, however, is forest fires occurring in disturbed areas (windthrow and bark beetle outbreak areas), which are comparable in severity and danger to the most serious forest fires. In this study, we describe the current situation in Central European countries in terms of fire protection for disturbed areas in managed forests and forest stands left to spontaneously develop (secondary succession). If a country has regulations and strategies in this area, they are often only published in the local language. In this review, we combine information from all Central European countries and summarize it in a unified international language, provide an opportunity for local authorities to express their own experiences, and integrate data from worldwide scientific research. Thus, this paper may be considered a universal guide for managing fire protection and preparedness in disturbed areas and can serve as a reference for the establishment of strict legislative rules at the state level. These laws must be obligatory for all stakeholders in individual countries. The motivation for this study was two large forest fires in an area left to spontaneously develop in the Bohemian Switzerland National Park in the Czech Republic and Harz Mountains in Germany in the summer of 2022. These incidents revealed that fire prevention legislation was inadequate or nonexistent in these areas. The strategy of the European Union is to increase the size of protected areas and spontaneous development areas. Therefore, we consider it necessary to provide governments with relevant information on this topic to create conditions for better management of these destructive events.

The suggestion has been made within the wildland fire community that the rate of spread in the upper portion of the fire danger spectrum is largely independent of the physical fuel characteristics in certain forest ecosystem types. Our review and analysis of the relevant scientific literature on the subject suggest that fuel characteristics have a gradual diminishing effect on the rate of fire spread in forest and shrubland fuel types with increasing fire danger, with the effect not being observable under extreme fire danger conditions. Empirical-based fire spread models with multiplicative fuel functions generally do not capture this effect adequately. The implications of this outcome on fire spread modelling and fuels management are discussed. [ABSTRACT FROM AUTHOR]

• Determining the equations of wavefronts and wave rays by Randers geodesics. • Providing the model of wildfire propagation by Huygens' principle. • Determining the paths through them the fire reaches a special place. • Determining the paths through which the fire spreads faster. Here, by using the validity of the Huygens' envelope principle for wavefronts in Randers spaces, we present some models for wildfire propagation in a flat land under the presence of wind. The wind could be constant or space-dependent. In the models, the height of the propagation is considered, trajectories of fire particles are tracked, and the equations that give the wavefront at each time are provided. Furthermore, we determine the paths of great importance in the process of wildfire management, called strategic paths. These paths can be used to determine the locations of barriers that we make to block the fire and stop it from propagation toward some special area; or to determine the paths through which the fire surrounds, for instance, the transmission lines of the power system. Finally, we provide several interesting examples of spreading the wildfire with different conditions. We implement the examples in the MATLAB environment to solve and provide the models of fire propagations. [ABSTRACT FROM AUTHOR]

An analysis of a dataset (n = 58) of high-intensity wildfire observations in cured grasslands from southern Australia revealed a simple relationship suitable for quickly obtaining a first approximation of a fire's spread rate under low dead fuel moisture contents and strong wind speeds. It was found that the forward rate of fire spread is approximately 20% of the average 10-m open wind speed. The data on rate of fire spread and 10 m open wind speed ranged from 1.6 to 17 and 20 to 62 km h−1, respectively. The validity of the resulting rule of thumb was examined across a spectrum of burning conditions and its performance was contrasted against that of established empirical-based fire spread models for three different grassland fuel conditions currently used operationally in Australia. The 20% rule of thumb for grassfires produced error statistics comparable to that of the fire spread rate model for grazed or cut grass fuel conditions as recommended for general use during the summer fire season in southern Australia. [ABSTRACT FROM AUTHOR]

An analysis of a dataset (n = 58) of high-intensity wildfire observations in cured grasslands from southern Australia revealed a simple relationship suitable for quickly obtaining a first approximation of a fire’s spread rate under low dead fuel moisture contents and strong wind speeds. It was found that the forward rate of fire spread is approximately 20% of the average 10-m open wind speed. The data on rate of fire spread and 10 m open wind speed ranged from 1.6 to 17 and 20 to 62 km h−1, respectively. The validity of the resulting rule of thumb was examined across a spectrum of burning conditions and its performance was contrasted against that of established empirical-based fire spread models for three different grassland fuel conditions currently used operationally in Australia. The 20% rule of thumb for grassfires produced error statistics comparable to that of the fire spread rate model for grazed or cut grass fuel conditions as recommended for general use during the summer fire season in southern Australia.

Thermal runaway (TR) and the resulting fire propagation are still critical issues puzzling the application of lithium-ion batteries in energy storage system (ESS). A fire propagation model including accurate TR propagating process assists in understanding the battery failure mechanism and determining the safety-optimal design of ESS, while its development is hindered by the complexity of simulating large-scale spatial system and interactions between TR and fire. In this work, a coupled semi reduced-order model (SROM) toward real-scale ESS is developed to capture battery TR and fire propagation behavior. Wherein, meshless methods are implemented for battery cluster by constructing thermal resistance network to simulate heat generation and transfer, which simultaneously couples a mass flowing network to address gas generation and subsequent jet. Full-order CFD model is adopted to simulate burning behavior in external fluid with higher precision. This model can accurately capture cross-scale parameters, including temperature evolution at cell-level and heat release rates (HRR) at system-level, as confirmed by experiments. Simulation results elucidate the failure propagation mode and mechanism from cell-to-cell to module-to-module levels. The significant impact of triggering position on fire behavior is also revealed that TR originating from the cluster center causes rapider fire growth and larger peak HRR during fire propagation. The SROM covers entire phenomena chain from cell-level to system-level, which can serve as new guidelines for designing and running safer ESS. • A semi reduced-order model for fire propagation of lithium-ion battery is proposed. • Model balances fidelity and efficiency of battery simulation at large-scale system. • Model covers entire event chain of thermal runaway from cell-level to system-level. [ABSTRACT FROM AUTHOR]

A stochastic model based on a combination of the cellular automata approach for forest fires and a random walk for firebrands and hot gases has been further developed and used to simulate the Marshall fire, Colorado, December 2021. Typical heat release profiles for burning wooden houses from the literature were used to distill information on the burning duration and ignition delay time needed to model the hours-long firebrand emission from wooden buildings in the Marshall area during this fire. In addition to information on vegetation and housing structures from in-person inspection, satellite images were used to estimate various model parameters. The results give reasonable predictions for the extent of the fire and its time evolution. A parametric analysis further highlighted the sensitivity of predictions to the parameters used in the model and suggested areas for improvement. The very low computational cost of the model, ease of operation, and acceptable accuracy suggest that the proposed framework can be used for operational decision-making and damage assessment. [ABSTRACT FROM AUTHOR]

• Naturally stacked biomass straw fuel was ignited from an initial point-source fire. • Straw combustion process presented merged annular stage and separated annular stage. • Outside flame front spread linearly, and spreading rate raised with stacked diameter and thickness. • Quantitative modeling of mass loss rate and flame temperature were established. The combustion of biomass straw that ignited by a fire point is an important latent danger form of wildfire. The investigation of development of the straw burning are essential for the efficient and safety utilization of biomass straw as a typical fuel. In this paper, the naturally stacked straws with diameters of 60 cm, 90 cm, and 120 cm and thicknesses from 2.0 cm to 12.2 cm were ignited from a point-source fire. The fire propagation and combustion characteristics including propagation stage, flame spreading rate, mass loss rate (MLR), and flame central temperature were measured and analyzed. The results showed that the straw combustion process was divided into four typical stages, namely the center combustion stage, merged annular stage, separated annular stage, and decay stage. The combustion area between the inside and outside flame front forms an annular shape, thus forming a hollow structure in the flame. The outside flame front spreads outward linearly with the spreading rate approximately rising with the increase of diameter and thickness. The peak of MLR is determined by diameter and thickness, hence an MLR quantitative model was constructed as m ′ / S L ̇ ″ h ∝ D eq 2.391 . The exponential function between the dimensionless flame temperature T f - T ∞ T ∞ and the z - z 0 m ̇ - 2 / 5 was established. The inclined trend was becoming more obvious with a smaller negative slope in the three longitudinal regions. [ABSTRACT FROM AUTHOR]