Firing Line Research Articles

Exposure to lead-free frangible firing emissions containing copper and ultrafine particulates leads to increased oxidative stress in firing range instructors

BackgroundSince the introduction of copper based, lead-free frangible (LFF) ammunition to Air Force small arms firing ranges, instructors have reported symptoms including chest tightness, respiratory irritation, and metallic taste. These symptoms have been reported despite measurements determining that instructor exposure does not exceed established occupational exposure limits (OELs). The disconnect between reported symptoms and exposure limits may be due to a limited understanding of LFF firing byproducts and subsequent health effects. A comprehensive characterization of exposure to instructors was completed, including ventilation system evaluation, personal monitoring, symptom tracking, and biomarker analysis, at both a partially enclosed and fully enclosed range.ResultsInstructors reported symptoms more frequently after M4 rifle classes compared to classes firing only the M9 pistol. Ventilation measurements demonstrated that airflow velocities at the firing line were highly variable and often outside established standards at both ranges. Personal breathing zone air monitoring showed exposure to carbon monoxide, ultrafine particulate, and metals. In general, exposure to instructors was higher at the partially enclosed range compared to the fully enclosed range. Copper measured in the breathing zone of instructors, on rare occasions, approached OELs for copper fume (0.1 mg/m3). Peak carbon monoxide concentrations were 4–5 times higher at the partially enclosed range compared to the enclosed range and occasionally exceeded the ceiling limit (125 ppm). Biological monitoring showed that lung function was maintained in instructors despite respiratory symptoms. However, urinary oxidative stress biomarkers and urinary copper measurements were increased in instructors compared to control groups.ConclusionsConsistent with prior work, this study demonstrates that symptoms still occurred despite exposures below OELs. Routine monitoring of symptoms, urinary metals, and oxidative stress biomarkers can help identify instructors who are particularly affected by exposures. These results can assist in guiding protective measures to reduce exposure and protect instructor health. Further, a longitudinal study is needed to determine the long-term health consequences of LFF firing emissions exposure.

Democracy and Theatre in Catalonia Since 1975

Democracy and Theatre in Catalonia Since 1975

Young forests and fire: Using lidar–imagery fusion to explore fuels and burn severity in a subalpine forest reburn

AbstractAnticipating fire behavior as climate change and fire activity accelerate is an increasingly pressing management challenge in fire‐prone landscapes. In subalpine forests adapted to infrequent, stand‐replacing fire, self‐limitation of burn severity in short‐interval fire is incompletely understood. Spatially explicit fuels data can support assessments of landscape‐scale fire risk and fuel feedbacks on burn severity. For a ~1450‐km2 largely forested landscape in the US Northern Rocky Mountains, we used airborne lidar and imagery to predict and map canopy and surface fuels. In a fire that burned mature (>125‐year‐old) and also reburned young (~30‐year‐old) subalpine forest, we then asked: (1) How do prefire fuels and burn severity compare between young and mature forests that burned under similar fire weather conditions? (2) How well do prefire fuels and forest structure predict burn severity under extreme versus moderate fire weather? Lidar–imagery fusion predicted fuel characteristics with high accuracy across forest and shrubland vegetation. Young postfire forests had abundant, densely packed canopy fuels, and both young and mature forests had similar canopy fuel loads and coarse wood biomass. Under similar weather conditions, young and mature forests burned at similar severity. Overall, fuels were weak predictors of burn severity and, surprisingly, better predicted severity under extreme rather than moderate fire weather. Our findings are relevant for subalpine landscapes increasingly dominated by young lodgepole pine (Pinus contorta var. latifolia) forests vulnerable to short‐interval fire and provide a benchmark to assess how fuels influence burn severity in future fires. Fire managers should continually reassess fuels and update expectations about fire behavior as landscapes change. Although recovering postfire forests can limit fire spread and severity for a period of time, our results suggest that young subalpine forests in the Northern Rocky Mountains have sufficient fuel loads to burn at high severity and should not be considered effective fire breaks.

Review Essay: Implicated in violence: Socio-legal approaches to international humanitarian law and international criminal law

Abstract Kamari Maxine Clarke, Affective Justice: The International Criminal Court and the Pan-Africanist Pushback (Duke University Press 2020). Noura Erakat, Justice for Some: Law and the Question of Palestine (Stanford University Press 2019). Neve Gordon and Nicola Perugini, Human Shields: A History of People in the Line of Fire (University of California Press 2020). Craig Jones, The War Lawyers: The United States, Israel, and Juridical Warfare (Oxford University Press 2020). Rebecca Sutton, The Humanitarian Civilian: How the Idea of Distinction Circulates Within and Beyond International Humanitarian Law (Oxford University Press 2021).

DOZER LINES INFLUENCE POST-FIRE PLANT COMMUNITY RECOVERY

As wildfires increase in extent and intensity and threaten local communities, active suppression tactics are becoming more common, including the creation of fire lines. Post-fire, these sites can become populated with non-native species and risk type conversion if native species recovery is lacking. Minimal research exists on the plant community trajectory of these mechanically disturbed sites. We studied the 32-Fire located east of Chico, CA. A fire line approximately 0.5 km long ranging in width from 6–12.2 m was created by a bulldozer. To assess plant recovery, we established plots in three pre-fire vegetation types: California Black Oak (Quercus kelloggii Newb.), Manzanita (Arctostaphylos manzanita Parry), and Wedgeleaf Ceanothus (Ceanothus cuneatus [Hook.] Nutt.) within three disturbance levels: burned, unburned (reference), and disturbed dozer line. Sites were sampled in 2018 (six-months post-fire) and in 2019 (18-months post-fire). In 2019, dozer line sites in the Manzanita and Wedgeleaf Ceanothus vegetation types did not have the dominant species found in similar unburned or burned sites. Across all vegetation types, dozer line sites had significantly higher average percent non-native species cover, compared with respective burned (P < 0.001, 95% C.I. = 33.2, 64.8) and unburned areas (P < 0.001, 95% C.I. = -77.2, -45.5). While unburned Wedgeleaf sites average non-native cover was 11% (SD = 9) in 2018 and 20% (SD = 5) in 2019, Wedgeleaf dozer line sites average non-native cover remained high between survey years at approximately 85%. Manzanita dozer line sites had average nonnative cover of 76% (SD = 16) and 57% (SD = 25) in 2018 and 2019, respectively, while unburned Manzanita had 9% (SD = 9) and 16% (SD = 16). Manzanita and Wedgeleaf Ceanothus species present on the study site are obligate seeders. Since neither species survived the implementation of the dozer line and no new recruitment of these species was observed, future recruitment of obligate seeders in these areas is unlikely. This suggests that dozer line sites with obligate seeders as dominant or co-dominant species are at risk of type conversion from native chaparral to annual grasslands dominated by non-native species.

Numerical Simulation Research on Cable Fire of Urban Underground Comprehensive Pipe Gallery Using Suffocating Fire Extinguishing Method

The integrated pipe corridor cable is the lifeblood of urban power transmission and has a high fire hazard. Once a fire breaks out, the electricity supply of the entire city will be paralyzed. Aiming at the cable fire in the urban underground integrated pipe gallery and combining with the Pyrosim software, this paper adopts the method of fire suffocation, to study the changes of fire smoke in the pipe gallery. The results show that in the pipe gallery of the 200m fire compartment, the open flame can be completely extinguished in 264s under the simulated working condition of the fire source power of 1MW. At 300s after the cable fire, the temperature in the pipe gallery basically maintained a stable state of 40°C. After the fire broke out, the O2 concentration dropped rapidly and plunged to 16% within 195s and it was completely consumed in 515s. Studies have shown that the use of suffocation to extinguish fires produces less fire smoke in the pipe gallery, and the visibility can be well maintained above 30m.

Warmer Nights Are Adding Fuel to Nighttime Fires

Cool, moist nights are rarer than they were a few decades ago, and that’s giving wildfires an edge over crews trying to hold fire lines.

Video Exposure Monitoring and Position Tracking for Evaluating Particulate and Gas Exposures in a Fully Enclosed Small Arms Firing Range.

The exposure environment in small arms firing ranges is dynamic since ventilation conditions vary in space and time and instructors continuously move around throughout the range. Understanding the impact of engineering controls and instructor behavior on the levels of particulates and gases in the breathing zone is required for providing recommendations to mitigate exposure. In this study, video exposure monitoring (VEM) and position tracking technologies were used in conjunction with real-time measurements of ultrafine particle (UFP) and carbon monoxide (CO) exposures in the breathing zone of instructors in an enclosed small arms firing range. VEM was completed using Enhanced Video Analysis of Dust Exposure 2.1 developed by the National Institute for Occupational Safety and Health. With this program, video recordings of Combat Arms instructor activity were synced with exposure data collected in real-time during small arms training. Position tracking was completed using a system by Pozyx, which uses ultra-wideband (UWB) technology. Position tracking data was aligned with real-time sensor data via time-synchronization. VEM identified that the largest peaks in UFP and CO concentrations generally occurred when instructors were close to the firing line assisting shooters during live fire and when instructors were located near the center of the range near the back wall where the air supplies transition between the Left-Hand-Side (LHS) and Right-Hand-Side (RHS). The UWB position tracking results agreed with the VEM results, confirming that peak exposures occurred when firing range instructors were near the center of the range close to the back wall where the LHS and RHS air supplies transition. Without these exposure visualization technologies, this observation could not have been made. Thus, exposure visualization is a valuable tool to identify gaps in exposure assessment, although future technologies should focus on automation to expedite analysis.

Simulating Potential Impacts of Fuel Treatments on Fire Behavior and Evacuation Time of the 2018 Camp Fire in Northern California

Fuel break effectiveness in wildland-urban interface (WUI) is not well understood during downslope wind-driven fires even though various fuel treatments are conducted across the western United States. The aim of this paper is to examine the efficacy of WUI fuel breaks under the influence of strong winds and dry fuels, using the 2018 Camp Fire as a case study. The operational fire growth model Prometheus was used to show: (1) downstream impacts of 200 m and 400 m wide WUI fuel breaks on fire behavior and evacuation time gain; (2) how the downstream fire behavior was affected by the width and fuel conditions of the WUI fuel breaks; and (3) the impacts of background wind speeds on the efficacy of WUI fuel breaks. Our results indicate that WUI fuel breaks may slow wildfire spread rates by dispersing the primary advancing fire front into multiple fronts of lower intensity on the downstream edge of the fuel break. However, fuel break width mattered. We found that the lateral fire spread and burned area were reduced downstream of the 400 m wide WUI fuel break more effectively than the 200 m fuel break. Further sensitivity tests showed that wind speed at the time of ignition influenced fire behavior and efficacy of management interventions.

Modelling extinction/re-ignition processes in fire plumes under oxygen-diluted conditions using flamelet tabulation approaches

The main objective of this article is to investigate the capability of the flamelet progress variable (FPV) model to capture the extinction processes observed in under-ventilated fire scenarios. To this end, large eddy simulation (LES) of the methane line fire plumes in oxygen-reduced environments down to global extinction, investigated experimentally at the University of Maryland (UMD), is performed. Two experimental burner configurations, that differ by the presence (anchored) or not (non-anchored) of an oxygen anchor to stabilise the flame base, are considered leading to two different extinction modes. Both the FPV and the steady laminar flamelet (SLF) model coupled with a presumed filtered density function (FDF) are considered. The Rank Correlated Full Spectrum k-distribution (RCFSK) model is used as a gas radiative property model. In both non-anchored and anchored scenarios, the FPV model reproduces with fidelity the evolution of the fire plume structure, radiative loss, and combustion efficiency with decreasing down to global extinction, without introducing any adjustable constant. The extinction in the non-anchored scenario occurs owing to flame-based detachment coupled to the generation of a buoyancy-driven vortex and is found to be very sensitive to the grid resolution in the near burner region. The present results suggest that these processes can be adequately resolved with a spatial resolution of 2.5 mm in this region. The SLF model, for its part, provides reliable predictions comparable to the FPV as long as no local extinction/re-ignition process occurs.

Investigating Fire Protection Condition in the Units of Imam Khomeini Hospital Tehran, Iran

Background: Various studies indicate that in many cases, fire has broken out in hospitals. Objectives: This study aims to assess fire protection in the selected units of Imam Khomeini hospital located in Tehran, Iran in 2020. Methods: In this descriptive-analytic study, first, a researcher-made checklist was developed for the data collection by valid scientific resources (CVI=0.90 and CVR&gt;0.62). After revising and the final confirmation of reliability, the checklist was separately completed by two members of the risk management committee in 22 units of Imam Khomeini hospital, Tehran, Iran. Cronbach’s weighted Kappa statistical test was calculated. Results: The domain of Ability and Capability of Fire Prevention was 66.1%; the domain of Responsiveness was 65.1%, and the domain of Urgent Evacuation Ability was 27.3%. In the domain of Responsiveness, the highest scores were relevant to accessing fire extinguishers cylinder in the units (95.5%) and holding fire extinguishing practice courses, and doing seasonal practices with that region’s fire station (90.9% for both). The highest scores in the domain of Urgent Evacuation Ability were assigned to accessing adequate ambulances to evacuate patients (90.9%) and mapping the units as well as determining patient evacuation routes when a fire breaks out (72.7%). Conclusion: The essential protection measures should be taken in order to improve the hospitals’ fire protection by better access to the exits, increasing the number of the exits and standardizing the emergency exits, enhancing the due fire extinguishing practices and hospital evacuation as well as training the staff.

An experimental study on thermal runaway and fire behavior of large-format LiNi0.8Co0.1Mn0.1O2 pouch power cell

Lithium-ion batteries are widely promoted in contemporary energy storage and electric vehicles, but battery fires frequently occur, so their thermal runaway and fire behaviors need to be deeply understood. This study investigates the thermal runaway and fire behaviors of 78 Ah LiNi0.8Co0.1Mn0.1O2 pouch batteries under 10 - 50 kW∙m-2 incident heat fluxes, including the combustion behaviors, heat release, and flame temperature. Heat release rate (HRR) based on the oxygen consumption principle (OCP) is modified by measuring the oxygen production of the fully charged cathode during continuous heating. Results show that the heat contributed by the oxygen released from the cathode is negligible (accounting for about 5% of the total heat release (THR)). The 100% and 0% SOC cells follow two different kinds of combustion behaviors. The incident heat flux has little influence on the total burning time, HRR, and THR of 100% SOC cells. It is found that there is a correlation between the time to ignition and the incident heat flux, namely tig∼(Tig−T0q˙′′)0.71. Besides, a flame centerline temperature distribution description model based on a line fire source is established, which is helpful to understand the battery flame structure, and provides a reference for thermal protection and evaluation of the thermal hazard of power supply applications.

Fire Scenario Zone Construction and Personnel Evacuation Planning Based on a Building Information Model and Geographical Information System

The spatial–temporal simulation of fire disasters and evacuation route planning are important research fields for urban emergency responses and are primary tasks that answer complex questions after fires break out. The increasing demand for refined building information models will sharply increase the calculated and analyzed quantity. This demand presents a challenge for fire emergency responses based on massive building information. In this paper, the principle of the realistic worst case (RWC) is introduced into fire simulation and evacuation route planning. Taking the library of the Nanjing Forestry University as the study object, the spatial–temporal characteristics of the influential environmental factors of the fire are simulated, such as the meteorological elements, building structure, and building skin. The scenario zones that are relatively prone to fire are selected using an overlay analysis across the four seasons. Then, the risk threshold for evacuating personnel is analyzed in the fire zone according to international standards and firefighting criteria. Specific parameters are determined based on the analysis of the above. The growing trends for fires across the four seasons are simulated with scenario zones as the starting positions and incorporate factors such as temperature, carbon monoxide, and smoke. Lastly, a life safety assurance path (LSAP) for personnel evacuation is designed based on an indoor road network and path search algorithm. The evacuation planning result is compared with the traditional shortest-time path and shortest-distance path. Based on the study results, fire scenario zones can improve the speed and operating efficiency of spatial–temporal simulation models of fire and can also support path planning and design for emergency responses.

Romanians in Austria-Hungary in the Years of “the Great War”. The Perspective of Visual Sources

"The present article is based on two research experiences that were resulted in the printing of two volumes that included visual documents. In the present article, our aim is to present the content categories that can be found in the photographs and postcards with and about the Romanians from the Austrian-Hungarian monarchy who took part in the traumatizing experience of World War I. Thus, a first theme that is rich and varied included the “faces” of the officers, soldiers and, last but not least, the civilians, in different situations, contexts and stances imposed by the war’s developments. There are group photographs that contain a varying number of soldiers, from two – three persons, up to several dozens, along with individual photographs; in all of these photographs, there are soldiers and officers, together or separate. Next, there is a distinct category of visual materials, concerning propaganda; they are mostly illustrated postcards that circulated as correspondence between the firing line and the “home front”. The symbolism of the state authority, along with the image of the emperor and that of the imperial family, were a recurring presence in the imagistic content with which the Austrian-Hungarian postcards printed during the war tried to send a loyalist message or to consolidate it in the community’s mentality. The materials that are related to the course of the daily life near the front, as well as behind it, are particularly interesting; the photographs taken during the war usually depict non-fighting moments, the moments of rest, containing with varied and diverse themes. There is a special category of visual documents that have been preserved from the time of the war, depicting the suffering that was inflicted upon the participants and the manner in which it was “handled”. Thus, among the photographs that fall in this category, we encountered those of the wounded and hospitalized soldiers, the field hospitals and the personnel with medical attributions that served near the units. Another theme section directly connected to the previous one is represented by the physical embodiment of death along the front line: photographs of funerals, graves and military cemeteries. There is a category of visual sources, from both public and private collections, that related to the war “on the seas”, photographs and postal cards of the marine troops serving in the Empire; they were stationed at Pola, in the Adriatic Sea. The photographs taken during the Great War that depict soldiers alongside civilians are of particular interest. Mostly, they are soldiers together with their own family members (mothers, wives, children etc) that are depicted in photographs that were taken far from the front line, during leaves, when the soldiers could briefly re-join their native communities. The Romanians that served in the war, wearing the military uniform of the double monarchy and who left its sphere of loyalty, either by becoming prisoners or by voluntary desertion, is a theme that was not overlooked by the visual sources that have survived from that period. These photographs of prisoners and Romanian volunteers from the time of the Great War are also relevant for the geographic coordinates, very far from one another, where the course of the events carried the Romanian soldiers, from France to far-away Siberia, at Vladivostok. The document images from the time of the Great War allow for a sui generis dialogue with those “who are no more”, over a temporal gap of a century. The camera lens often captured expressive faces, whose identity is known in the cases in which the photographs include markings and notes, along with those that offer no additional information concerning those who took the photos or their subjects; in the latter case, we can say that these images are the anonymous bearers of war’s memory. These materials offer us today the unique privilege of visually “communicating” with our forbearers from a century ago, with the representatives of the humanity that plunged into the terrible adventure of World War I. Keywords: “The Great War”, Romanians, Austria-Hungary, visual sources, cultural history. "

Flame attachment and downstream heating effect of inclined line fires

Experiments were conducted to quantify downstream heating from inclined fires generated by a 25 cm wide, 5 cm deep gaseous line burner. A variety of orientation angles (θ) and fire heat-release rates (HRR) were employed simulating, at reduced scale, the dynamics of two-dimensional (2-D) inclined flame spread as found in wildland or building fires. The total heat flux q˙f″(x) to a nearly-adiabatic surface ahead of the burner was measured by a water-cooled total heat flux gage at different downstream locations (x). It was found that, with an increase in fire HRR or θ, q˙f″(x) increases. The same is true for both the flame projection length on the inclined surface (Lf,p) and the flame attachment length (La). The location of flame attachment divides a flame into an attachment region (0≤x≤La) and a liftoff region (La<x≤Lf,p). A scaling analysis was performed to correlate the modified non-dimensional heat flux q˙f*(x) and the normalized downstream distance x/La in these two regions as a piecewise power-law function. Lf,p is scaled by a non-dimensional HRR, Q˙θ*=Q˙/(ρ∞cpT∞(gcosθ)1/2D3/2L), together with the angle between a flame and an inclined surface (α). La is well represented by two derived non-dimensional quantities, L/Lf,0 and Lf,p/Lf,0 (Lf,0 is free flame height), based on the analysis of the balance between the buoyancy force of a flame (upward) and the inertial force due to air entrainment (horizontal). The quantitative comparison with previous flame spread tests over inclined PMMA samples demonstrates the effectiveness of the proposed correlations in predicting downstream heating of 2-D flame spread over inclined terrains.

Numerical Simulation of the Effect of Fire Intensity on Wind Driven Surface Fire and Its Impact on an Idealized Building

This paper presents an investigation on the effect of fire intensity of a wind driven surface fire, similar to a large wildfire, on an idealized structure located downstream from the fire source. A numerical simulation was conducted using an open source CFD code called FireFOAM, which is a transient solver for fire simulation and turbulent diffusion flames, supported by a large eddy simulation (LES) solver for incompressible flow. The numerical data were verified using the aerodynamic experimental data of a full-scale building model with no fire effects. An idealized cubic obstacle representing a simplified building with the dimension of 6 × 6 × 6 m; is considered downstream from the fire source. Different fire intensity values of the fire line representing different grassland fuels were simulated to analyse the impact of wind-fire interaction on a built area. To solve the problem, a coupled velocity and pressure method was applied through a PIMPLE scheme in FireFoam solver of OpenFoam platform. There is a good agreement between simulated results and experimental measurements with a maximum error of 18%, which confirms the validity and accuracy of the model. The results showed that by increasing the fire intensity; the velocity of the crosswind stream increases, which causes low-density air and generates an extra stream behind the fire plume. It was also found that increasing fire intensity from 10 MW/m to 18 MW/m raises the integrated temperature on the ground near the building and on the surface of the building by 26%, and 69%, respectively.

Study on Coupled Combustion Behavior of Two Parallel Line Fires

In this study, the interaction of two parallel line fires with a length-width ratio of greater than 50 was investigated and compared to a single line fire. Considering different length–width ratios and spacings between the fire sources, experiments were carried out to analyze the fire characteristics, such as the burning rate, the flame-merging state, the flame height, the flame tilt angle, and the flame length of the line fires. Its regularity was revealed by combining two mechanisms, namely, heat feedback enhancement and air entrainment restriction. The results revealed that the burning rate under different length–width ratios shows a uniform law, which increases first and then decreases with a greater spacing between the fire sources. There is a special relationship between the flame-merging probability Pm and the dimensionless characteristic parameters (S/ZC)/(L/d)0.27. Based on this relationship, a critical criterion of flame merging can be obtained as (S/ZC)/(L/d)0.27 = 2.38. In addition, the height and the length of the flame were studied to better describe the flame shape when the flame is tilted. Since the flame is bent, the flame length has an abrupt change at a specific position, and the inclination angle also has the same phenomenon. Finally, it was found that the influence of the length–width ratio on the line fires is relatively limited, which is further weakened under a greater length–width ratio.

Burning Rate and Flow Resistance Through Porous Fuel Beds: Axisymmetric Versus Line Fires

ABSTRACT The burning rate of wildland fuels is a poorly understood yet key fire behavior metric. Previous work has utilized wood cribs; however, it has not yet been addressed whether the burning behavior of a crib, an axisymmetric fire, can be representative of a line fire, a typical configuration in wildfires. In this study, airflow into two sides of the crib was physically blocked and the resulting burning rate was noted. Six crib designs with a range stick thicknesses and porosities were tested both on the ground and with a gap underneath. For most cases, blocking the sides had only a modest effect on the burning rate (up to 22% reduction). In these cases, axisymmetric fire sources may give an acceptable approximation for the burning rate of a segment of a line fire. However, for the cribs built with thinner sticks placed directly on the ground, the reduction was more dramatic (up to 45%) and the use of axisymmetric and line fire sources requires further consideration. Resistances to flow in both the horizontal and vertical directions within the crib were used to understand these trends and to provide a better qualitative picture of how flows govern the burning of cribs in general.

Interaction between two parallel fire fronts under different wind conditions

Wildfires often exhibit complex and dynamic behaviour arising from interactions between the fire and surrounding environment that can create a rapid fire advance and result in loss of containment and critical fire safety concerns. A series of laboratory experiments involving the interaction of two parallel fire lines on a uniform fuel bed without slope under the influence of wind is presented and discussed. The two fire lines are initially separated by a certain distance (1, 2 m) and the subsequent fire spread is described. The results show that the pyroconvective interaction between the two fire lines and ambient wind modified the rate of spread of the approaching fire lines and their associated spread characteristics, independently of the distance between them. A physical interpretation of fire evolution based on the dynamic interaction between two parallel fire lines under wind flow is proposed. We use a dimensionless physical parameter, the Froude number. The results also demonstrated the existence of a wind flow velocity between 1 and 2 m s−1, corresponding to a Froude number between 0.2 and 0.4 for which the rate of approach of the two merging fire lines is a minimum.

An analytical model for predicting the flame length of fire lines and tree crown scorching

In forest fires, the fire plume can heat tree crowns and cause the mortality of live vegetation, even though the surface fire spread is of low burning intensity. A lot of empirical or semi-empirical correlations have been built to link the fire intensity and flame height to the crown scorch height. These correlations lack the basic physical processes of heat transfer and thermal response of needles and leaves. Besides the flame height, the fire plume temperature and velocity are also of great importance to quantify the heat transfer to the tree crown. Accordingly, an analytical model, derived from a system of differential equations, describing the conservation of mass, momentum, energy, and chemical composition, is proposed to predict the properties of a fire plume from a line fire. The flame height predicted by the analytical model matches experimental measurements of small, medium, and large line fires, showing a considerable robustness of the proposed model. With an assumption of the lethal temperature of live vegetation, the analytical model can also predict the crown scorch height against available empirical correlations and experimental data. In addition, an analysis of the effect on the flame length of the distance between the fire and the ground surface indicates that it would be better to simulate the wildland fire front by a gaseous line fire above the ground surface. The effect of ambient air temperature and fireline residence time (or heating time of foliage) on the crown scorch height is also quantified. It is found that the hot plume can heat the live foliage to reach a lethal temperature of 60°C under a heating time of 60 s.