Firing Line Research Articles

Experimental and analytical study on inclined turbulent fire in still air. Part 1. Line fire

In this paper, an experimental and theoretical analysis is conducted on the behavior of the inclined turbulent line fires under different initial Froude numbers (Fr0) and initial flame angles (θ0). The flame temperature and flow fields are measured, and the flame geometry is extracted from video images. Experimental results show that the curvature of flame trajectory increases with the increase of Fr0 or the decrease of θ0. The axial temperature and flame length decrease as θ0 decreases under the same Fr0, indicating the enhancement of flame entrainment due to the cross stream-buoyancy. A prediction model to describe the flame motion is established by analyzing the mass and momentum equations. The model combined with the kinetic energy equation incorporates the effects of buoyancy and streamline curvature on the flame entrainment. The model predicts the flame trajectory and correlates the flame entrainment coefficient of turbulent line fires under different Fr0 and θ0. Model calculations show that the comprehensive effect of buoyancy and streamline curvature on the flame entrainment increases as Fr0 increases within a certain range or as θ0 decreases, in agreement with the experimental indications. The results of this paper are expected to help understand the flame motion and develop radiative heat transfer models of turbulent line fires.

Experimental and analytical study on inclined turbulent fire in still air. Part 2. Round fire

This paper reports an experimental and analytical study on non-vertical round turbulent jet fire. A series of propane jet fire tests are performed under different initial flame angles (θ0) and initial fuel velocities. The two-dimensional velocity and temperature fields of the flame are measured, and the flame geometry is determined from video images. Experimental results show that the flame entrainment is enhanced as θ0 decreases. The flame deflection-induced buoyancy flow plays an essential role in the local flame structure and turbulence. A model of round fire combined with a kinetic energy equation is established, in which the flame entrainment coefficient is analytically correlated with the buoyancy and streamline curvature. Model calculations reproduce the flame entrainment and flame trajectory, consistent with the experimental indications. Under the same burner area and heat release rate, the entrainment coefficient of round fire is greater than that of line fire, closely associated with the difference in integral buoyancy triggered by different burner geometries. The results of this paper may help understand the flame motion and predict the flame radiation of turbulent jet fires.

Predicting the rate of forest fire spread toward any directions based on a CNN model considering the correlations of input variables

ABSTRACT Modeling forest fire spread rate is a complex problem, and the existing models are unable to accurately predict the rate of fires spreading towards any directions. In this paper, a convolutional neural network (CNN)-based model is designed to predict the spread rate of forest fires spreading in any directions and using the spread direction as one of the model’s inputs. Several outdoor burning experiments were designed and conducted in order to obtain a dataset on which the model can be trained and validated. Correlation analysis was performed on the variables, and their positions are arranged in a fourth-order matrix according to the strength of their correlations to reflect the correlations in space for feature extraction by the CNN. A deep neural network (DNN)-based model is also designed for comparison to demonstrate the advantages of considering the correlation between variables. The comparison with the improved Wang’s model proves that the model proposed in this paper has higher prediction accuracy compared with the traditional model. The validation experiments were carried out in terms of fire spread rate or fire line’s position. The proposed spread model can provide the technical support for managing the forest fires.

The impacts of putting the Zaporizhzhia Nuclear Power Plant in the line of fire

AbstractThe armed forces of the Russian Federation captured the Zaporizhzhia Nuclear Power Station after their invasion to Ukraine in February 2022. In early August 2022, reports about shelling of the station ignited fear of a nuclear accident. Simultaneously, the disruption in the generation of electricity from nuclear energy has fueled a notable increase in the price of oil. The compounding effect of these developments on global health includes acute and chronic radiation exposure, food insecurity due to the potential contamination of the environment and the rise in the cost of essential commodities, and limited access to healthcare. International and national governance bodies need to take action in order to mitigate the effects of this incident on health and prevent similar events in the future.

Effects of spacing distance and fuel mass thickness on combustion and flame merging characteristics of two-line pool fires

Flame merging of line fires is very complex with the interaction of fire dynamics and fluid flow et al., which will often generate different burning behaviors. In this paper, the effects of spacing distance and fuel mass thickness on the combustion and flame merging characteristics of two n-heptane line pool fires were studied. With the dimensionless liquid fuel height H* (Fuel height/Groove depth) increase, the probability of flame merging, and the temperature of the additional air entrainment region gradually increase. The merging flame will change from no hole, with hole, hole increased to hole open stage with spacing distance increase. It is interesting to find that, the mass loss rate of each line fire is less than that of a single line fire burning alone, and the closer the distance is, the smaller the value is. Meanwhile, for a single or double linear fires at H* = 3/4, the mass loss rate is the greatest. By establishing a heat transfer model, it is demonstrated that at H* = 3/4, the ullage of the groove has a stabilizing effect on the flame, which makes the flame height the largest. The results of this study will enhance the understanding of the flame merging of line fires with different fuel masses.

“Send Forth the Very Best Ye Breed”: Captain Frederick S. Wild and the War in the Philippines, 1899–1902

“Send Forth the Very Best Ye Breed”: Captain Frederick S. Wild and the War in the Philippines, 1899–1902

Crack Analysis Due to Fatigue Load During Subsea Pipeline Installation

Most of the subsea pipelines in Indonesia are installed using the S-Lay method with the pipelay barges equipped with mooring spreads, tensioners, and stinger. During the subsea pipeline installation, static loads occur due to the pipeline configuration from the firing line of the pipelay barge up to the seabed. The pipe will experience axial tension and bending moment in two critical areas: overbend and sagbend. In addition, fatigue loads occur during subsea pipeline installation due to environmental loads (i.e., currents and waves). Defects that are found after welding will grow due to these fatigue loads. Crack analysis with a fracture mechanic approach known as Engineering Critical Assessment (ECA) is carried out by considering the fatigue load due to significant wave height variations for 0.5m, 1.0m, and 1.8m. BS 7910 is used as a standard reference to determine the allowable defects criteria for external and internal flaws. The depth of the defect (a) is simulated from a depth of 1mm – 3mm. The analysis found that the allowable defect length is decreased by 12.7% - 25.0% from a significant wave height of 0.5m to 1.8m for the external surface flaw. While for an internal surface flaw, the allowable defect length is decreased by 5.9% - 13.6% from a significant wave height of 0.5m to 1.8m. These results can be used as a basis for subsea pipeline installation contractors to perform fatigue load sensitivity and optimize the allowable defects based on the actual wave load at the site.

Effects of spacing distance and heat release rate on flame merging and burning characteristics of two ultra-long thin line fires

Effects of spacing distance and heat release rate on flame merging and burning characteristics of two ultra-long thin line fires

Using Virtual Fencing to Create Fuel Breaks in the Sagebrush Steppe

Wildfires are increasingly impacting ecosystem processes and ecological services provided by sagebrush rangelands in the western United States. Mitigating this problem involves actions taken before, during, and after fire. In recent years, there has been increased emphasis on prefire fuel management, including fuel breaks. Cattle grazing can be used as a tool to manage fine fuel loading within fuel breaks; however, spatially focusing grazing impacts inside a linear fuel break is challenging. We evaluated using virtual fencing (VF) technology for concentrating grazing impacts inside a 200-m wide, 3-km long fuel break within a 410-ha pasture in sagebrush steppe. The fuel break was bounded by four 35-m wide virtual fences, each consisting of boundaries for auditory (10-m wide) and electrical cues (25-m wide), and a traditional 5-strand barbed wire perimeter fence delineated the pasture perimeter. In June 2021 we introduced 16 dry cows and 23 cow/calf pairs into the fuel break following a 5-d VF training period; cattle were removed after 30 d. Cows were fitted with VF collars (calves not collared) that use Global Positioning System positioning to contain cattle inside fuel break boundaries and record animal locations at 5-min intervals. End-of-trial forage utilization was 48.5% ± 3.7% and 5.5% ± 0.7% for areas inside and outside of the fuel break, respectively. Daily percentage of cattle locations inside the fuel break was initially > 94% but declined to approximately 75% by the end of the trial. Percentage daily locations of dry cows and cow/calf pairs inside the fuel break was 98.5% ± 0.5% and 80.6% ± 1.1%, respectively (P < 0.001). Our data suggest virtual fencing can be a highly effective method of concentrating grazing to reduce herbaceous fuel biomass within linear fuel breaks. Efficacy of this method could be substantially impacted by use of dry versus cow/calf pairs.

Developing a firewater deluge monitoring and forecasting system based on GA-ARMA model

PurposeThe firewater deluge system (FDS) can provide water automatically through a deluge valve when a fire breaks out. However, there are many fire hazards caused by the abnormal operating state of the FDS. To monitor and predict the working state of the FDS, this paper aims to propose a firewater deluge monitoring and forecasting system using the Internet of Things (IoT) technology.Design/methodology/approachThe firewater deluge monitoring and forecasting system consists of three layers: the sensing layer, network layer and application layer. The firewater pressure obtained by the monitoring nodes was transmitted to the local gateway and then to the remote monitoring center. In the application layer, an autoregressive moving average (ARMA) model was put forward to forecast the firewater pressure. Furthermore, a genetic algorithm (GA) was proposed to perfect the order determination method of the ARMA model. Finally, a Web application was developed to display the real time and predicted working status of the FDS.FindingsThe predicted results show that the ARMA model improved by the GA (GA-ARMA) is significantly better than traditional ARMA models in terms of mean relative error, mean absolute error and mean square error. Moreover, the proposed system is demonstrated to be effective, and an early warning can be alerted to remind users of repairing abnormal FDS equipment ahead of fire dangers.Originality/valueThe proposed system cannot only be applied to the FDS of all buildings to avoid fire hazards by monitoring and predicting the working state of the FDS, but can also be widely used in other fields, such as environmental monitoring, intelligent logistics and intelligent transportation.

Application of BIM for Effective Construction Safety Management in High Rise Buildings

The construction industry has a higher occupational casualty rate than other industries. As a proactive approach to safety management, a good safety management system (SMS) can go a long way to help prevent accidents and occupational hazards. This work proposes the use of BIM 3D with the help of Autodesk Revit for the identification of hazards and risks at the designing stages and for implication and planning of effective safety measures. This is carried out from the inception of the project itself which later can be applied to the construction process based on efficient SMS. The SMS established is based on surveys conducted on 45 personnel in the construction industry. The top 5 important issues found to be associated with site safety were: Exposed Rebars; Laboures and Visitors without ID; CCTV monitoring of site; Signs not secured properly; Access to Fire Engine and personnel in case of fire break out.

Situating ‘law’ as ‘culture’ in scholarly discourse on the International Criminal Court: a reflection on Fraser and McGonigle Leyh's Intersections of Law and Culture at the International Criminal Court

Within the rich literature on the International Criminal Court (ICC), across international criminal law scholarship, transitional justice and international relations, the study of ‘law and culture’ has a lengthy pedigree. After the ICC came into operation on 1 July 2002, several years followed before the first monographs on the Court's law and culture were published, notably Sarah Nouwen's Complementarity in the Line of Fire (2013) and Phil Clark's Distant Justice (2018). This delay reflected the years of field-based research necessary for empirically minded scholars to usefully comment on the Court. The writing of these scholars was informed by long periods spent in the field in ICC situation countries, enabling them to bring a meaningful understanding of the lives of affected communities to their analysis of the Court's impact. Clark's book, for instance, was the culmination of eleven years of research and fieldwork in ICC situation countries (Clark, 2018). These extensive periods of contact with victims and survivors have brought fresh perspectives on the ICC to those of us whose work is, necessarily, focused on proceedings in The Hague and who are, inevitably, unable to claim genuine long-term familiarity with the local meaning of the Court's proceedings for those whose lives we believe or hope we are (positively) impacting. Well-executed field-based research has so much to offer because it can be at once intellectually distanced from court proceedings in The Hague, while intellectually proximate to the locus delicti of international criminal justice in affected communities.

Modeling wildfire risk in western Iran based on the integration of AHP and GIS.

This study aimed at delineating the wildfire risk zones in a fire-prone region located in a rarely addressed area of western Iran (Paveh city)by assessing the potential of factors such as NDVI, topographic factors (elevation, slope, and aspect), land cover, and evaporation in explaining the fire occurrence probability. Analytic hierarchy process (AHP) and geographical information system (GIS) methods were used synergistically to integrate the mentioned factors into analysis, following an informed categorization of each factor based on the information on previous fire occurrence. In the AHP process, elevation and evaporation data were considered to be the most critical factors. It was found that the predicted wildfire risk areas were in agreement with past fire events by the use of the methodology proposed by this study. Accordingly, the study's final wildfire risk map indicated that approximately 64.7% of the study area is located in the high- and very high-risk zones. Land-use planners and decision-makers may use the developed map to setup and implement fire prevention strategies and enhance or develop the fire-surveillance logistics and infrastructure, including but not limited to the positions of fire watchtowers, fire lines, and fire sensors, with the aim to minimize potential fire impacts.

Effect of fire spread, flame characteristic, fire intensity on particulate matter 2.5 released from surface fuel combustion of Pinus koraiensis plantation- A laboratory simulation study.

PM2.5 is one of major pollutants emitted from forest fires. High PM2.5 concentration not only affects short-term human respiration health, but also poses a long-term threat to human cardiopulmonary functionality. Therefore, it is of great importance to quantitatively assess the PM2.5 released by forest combustion in forest fire studies. In this study we examine relationships between the PM2.5 concentration and environment and fuel characteristics laboratory experiments. In the experiments, fuel beds with controlled moisture contents and loads were first built; then 144 ignition experiments were conducted for various combinations of wind speeds using a wind tunnel device. Fire behavior characteristics and PM2.5 concentrations released from fuel combustion were measured and analyzed. The experimental results show that the relationship between fire characteristics, fire intensity and the influencing factors of wind speed, fuel moisture content, and fuel load can be explained by the fundamental theory of forest combustion. Although PM2.5 concentration rises with the increase of wind speed, the decrease of fuel moisture content, and the increase of fuel load, there appears to be a fuel load threshold for a given combination of wind speed and fuel moisture content that the increase of PM2.5 concentration decelerates quickly after the load passes the threshold value. After screening fire behavior characteristics that affect PM2.5 concentration, we found that fire line intensity and flame width are the ones with the strongest association with the concentration. With flame width as independent variable, we have built two regression models to predict PM2.5 and fire line intensity which are treated as dependent variable; the models have high accuracy with R2=0.92 for predicting PM2.5 and R2=0.97 for predicting fire line intensity. Study results can be used as reference to protect the health of forest fire fighters, and can be helpful for forest fire smoke management.

Numerical Simulation of Smoke Control in Underground Space

As the underground space is relatively closed compared to other buildings, the space is hardly connected to the outside world through entrances and exits, which makes it difficult to ventilate and exchange heat with the outside. In this case, it is easy to cause a large number of casualties when a fire breaks out. When the fire happens smoke will be discharged merely by the mechanical exhaust, and air system should work simultaneously to replenish the oxygen inside. By setting four-group models, the paper analyzes the strategies for smoke extraction and air makeup in the underground construction. The paper points out that when the fire happens in a smoke bay, the neighborhood smoke extraction fan should be opened and the air makeup system should not be located at the top to disturb the smoke layer. By comparing and analyzing the performance of the smoke extraction and air conditioning system, the casualties caused by the high temperature toxic smoke from the fire can be reduced as far as possible.

Evacuation speed of human beings in road tunnels at different altitudes

There is an increasing number of road tunnels constructed in high-altitude areas of China. Generally, a tunnel is long and narrow. Therefore, when a fire breaks out in a tunnel, it is difficult to get rid of the smoke and the heat, which poses a threat to stranded people. The walking speed of people is the critical factor determining the evacuation time, particularly in high-altitude areas where the ambient pressure is low. In this study, a series of field tests were conducted by considering the environmental parameters to explore the effects of altitude on the people’s walking speed, and the considered parameters include the blood oxygen saturation of people, their heart rate and its variability parameters, ratings of perceived exertion, and walking speed. The results show that ambient pressure, which is about 97 kPa at an altitude of 500 m, decreases to approximately 64 kPa at an altitude of around 3850 m. In other words, the ambient pressure decreases with the increase in the altitude, and the difference in illumination between the internal tunnel and open environment is obvious. More specifically, several factors, including gender, age, tunnel environment, and altitude influence the walking speed, and corresponding reduction coefficients are introduced to reflect the influence of the factors on the walking speed. Finally, based on the field data, a reliable formula is proposed to predict the walking speed at different altitudes.

The Surviving Rate of IC-Planar Graphs

Let k and n be two positive integers. Firefighting is a discrete dynamical process of preventing the spread of fire. Let G be a connected graph G with n vertices. Assuming a fire starts at one of the vertices of G, the firefighters choose k unburned vertices at each step, and then the fire spreads to all unprotected neighbors of the burning vertices. The process continues until the fire stops spreading. The goal is to protect as many vertices as possible. When a fire breaks out randomly at a vertex of G, its k-surviving rate, ρk(G), is the expected number of saved vertices. A graph is IC-planar if it has a drawing in which each edge cross once and their endpoints are disjoint. In this paper, we prove that ρ4(G)&gt;1124 for every IC-planar graph G. This is proven by the discharging method and the locally symmetric of the graph.

Fingering instability in wildfire fronts

A two-dimensional model for the evolution of the fire line – the interface between burned and unburned regions of a wildfire – is formulated. The fire line normal velocity has three contributions: (i) a constant rate of spread representing convection and radiation effects; (ii) a curvature term that smooths the fire line; and (iii) a Stefan-like term in the direction of the oxygen gradient. While the first two effects are geometrical, (iii) is dynamical and requires the solution of the steady advection–diffusion equation for oxygen, with advection owing to a self-induced ‘fire wind’, modelled by the gradient of a harmonic potential field. The conformal invariance of this coupled pair of partial differential equations, which has the Péclet number $\textit {Pe}$ as its only parameter, is exploited to compute numerically the evolution of both radial and infinitely long periodic fire lines. A linear stability analysis shows that fire line instability is possible, dependent on the ratio of curvature to oxygen effects. Unstable fire lines develop finger-like protrusions into the unburned region; the geometry of these fingers is varied and depends on the relative magnitudes of (i)–(iii). It is argued that for radial fires, the fire wind strength scales with the fire's effective radius, meaning that $\textit {Pe}$ increases in time, so all fire lines eventually become unstable. For periodic fire lines, $\textit {Pe}$ remains constant, so fire line stability is possible. The results of this study provide a possible explanation for the formation of fire fingers observed in wildfires.

Short-Term Vegetation Response to Bulldozed Fire Lines in Northern Great Plains Grasslands

A bulldozed fire line is a fire-suppression technique that limits fire movement by altering fuel continuity through vegetation removal and mineral soil exposure. The ecological impacts of a bulldozed fire line may exceed the effects of the fire itself through lasting changes in the soil and vegetation properties; however, little research has been performed to quantify these impacts in grassland systems. In this study, we compared vegetation properties among burned, unburned, and bulldozed fire line conditions on two August 2012 grassland wildfires in Montana. Standing biomass, by growth form, was quantified in 2013 and 2014, and compared using a generalized linear model. Perennial grass production was significantly reduced, while annual grass and annual forb biomass increased in response to the fire line treatment. Shrub and total vegetation standing crop were reduced in response to the fire line in 2013; however, the treatment effects were diminished by 2014. The burned and unburned treatments were generally similar within two years post-fire. The loss of perennial grasses and invasion of competitive annual grasses such as cheatgrass (Bromus tectorum L.) may limit the vegetation recovery of the fire line and promote further invasion of annual grasses into these systems. The marginal impact of the fires on these plant communities suggests the need to limit the use of ad hoc bulldozed fire lines as a suppression activity. If a bulldozed fire line is constructed, we suggest limiting soil disturbance by restricting blade depth to remove only surface vegetation and restricting bulldozer use to flat slopes, even if working with the contour, and incorporating re-seeding as part of or immediately after fire line construction.

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.