Treesearch

Non-steady and turbulent flames are commonly observed to produce flame contacts with adjacent fuels during fire spread in a wide range of fuel bed depths. A stationary gas-fired burner (flame wall) was developed to begin study of flame edge variability along an analagous vertical fuel source. This flame wall is surrogate for a combustion interface at the edge of a deep (1.8 meters), vertically arranged fuel bed. Thermocouple and heat flux measurements along the flame wall indicate most of the variability in flame convection occurs at frequencies lower than 10-20 Hz. The variability and...

Use of fire behavior models has assumed an increasingly important role for managers of wildfire incidents to make strategic decisions. For fire risk assessments and danger rating at very large spatial scales, these models depend on fire weather variables or fire danger indices. Here, we describe a method to simulate fire weather at a national scale that captures the same patterns of seasonality, spatial correlation and temporal correlation as the observed inputs. This method incorporates daily surface weather observations, which are incorporated into large scale models that give a grid of...

The study of buoyant convection for diffusion flames in wildland fires is critical to understanding heating and cooling dynamics related to particle ignition. Studies based on solid biomass fuels are made difficult by short flame residence time associated with fine fuels. An alternative is to use artificial fuel gas rather than relying on pyrolysis of solid fuels to produce the gas products for combustion. This paper reports on the design, construction, and testing of gas-fed burners used for the study of flame characteristics.

Living plants are often the primary fuels burning in wildland fire but little is known about the factors that govern their ignition behavior. Moisture content has long been hypothesized to determine the characteristics of fires spreading in live fuels but moisture content alone fails to explain observed differences in the ignition of various species at different times of the year. Furthermore, little concern has been given to balance between the moisture content and chemical composition of live fuels and how this balance of might affect the net energy required to produce the combustible...

The mechanism of flame propagation in wildland fire fuel beds is of critical importance for understanding and quantifying fire spread rates. Recent observations and experiments have indicated the dominance of flame propagation by direct contact between flames and unburnt fuel, as opposed to propagation via radiative heating alone. It is postulated that effects of radiative heating are offset by convective cooling associated with the turbulent, buoyant flames drawing in surrounding air, resulting in fuel surface temperatures too low to achieve ignition. Propagation via direct flame bathing...

Extreme weather often contributes to crown fires, where the fire spreads from one tree crown to the next as a series of piloted ignitions. An important aspect in predicting crown fires is understanding the ignition of fuel particles. The ignition criterion considered in this work is the critical mass flux criterion – that a sufficient amount of pyrolysis gases must be generated for a diffusion flame to be established above the surface. An apparatus was built to measure the critical mass flux for sustained flaming ignition of woody materials for varying environmental conditions (heat flux...

Fire behavior predictions, as well as measures of uncertainty in those predictions, are essential in operational and strategic fire management decisions. While it is becoming common practice to assess uncertainty in fire behavior predictions arising from variability in weather inputs, uncertainty arising from the fire models themselves is difficult to assess. This is the case with fires in crown fuels and the operational fire behavior models used in the United States, where model assumptions, such as fuel homogeneity and steady-state spread, limit the capability of those models to provide...

Crown fire poses challenges to fire managers and can endanger fire fighters. Understanding of how fire interacts with tree crowns is essential to informed decisions about crown fire. Current operational crown fire predictions in the United States assume homogeneous crown fuels. While a new class of research fire models, which model fire behavior with computational fluid dynamics (CFD), can be used to model fire in heterogeneous crown fuels, the potential impacts of variability in crown fuels have not yet been explored. In this study we introduce a new model, FUEL3D, which incorporates...

Cultural resources (CR) refer to the physical evidence of human occupations which archaeologist use to reconstruct the past. This includes the objects, locations, and landscapes that play a significant role in the history or cultural traditions of a group of people. CR include artifacts left by prehistoric aboriginal peoples and those of historical significance. Archaeological constituents, the basic units of archaeological analysis, consist of artifacts and features. Artifacts include carved objects, pottery and ceramics, flaked and ground stones, faunal and floral remains, glass, and...

Fire is one of the most significant threats for the Mediterranean forested areas. Global change may increase the wildland fire risk due to the combined effect of air temperature and humidity on fuel status, and the effect of wind speed on fire behaviour. This paper investigated the potential effect of the climate changes predicted for the Mediterranean basin by a regional climate model with a spatial resolution of 25 km. The data provided by the model were used in order to predict the changes in both the extreme fire weather days, and the fire behaviour for the different fire scenarios....