Conditions for the start and spread of crown fire

1977 ◽  
Vol 7 (1) ◽  
pp. 23-34 ◽  
Author(s):  
C. E. Van Wagner
Keyword(s):  
Heat Transfer ◽  
Bulk Density ◽  
Combustion Zone ◽  
Ground Surface ◽  
Conifer Forests ◽  
Crown Fire ◽  
Surface Phase ◽  
Conifer Forest ◽  
Crown Fires

Some theory and observations are presented on the factors governing the start and spread of crown fire in conifer forests. Crown fires are classified in three ways according to the degree of dependence of the crown phase of the fire on the ground surface phase. The crown fuel is pictured as a layer of uniform bulk density and height above ground. Simple criteria are presented for the initiation of crown combustion and for the minimum rates of spread and heat transfer into the crown combustion zone at which the crown fire will spread. The theory is partially supported by some observations in four kinds of conifer forest.

Modelling the rate of fire spread and uncertainty associated with the onset and propagation of crown fires in conifer forest stands

2017 ◽  
Vol 26 (5) ◽  
pp. 413 ◽  
Author(s):  
Miguel G. Cruz ◽  
Martin E. Alexander
Keyword(s):  
Monte Carlo ◽  
Average Rate ◽  
Fire Spread ◽  
Prediction Errors ◽  
Crown Fire ◽  
Conifer Forest ◽  
Fire Behaviour ◽  
Crown Fires ◽  
Deterministic Modelling ◽  
Eastern Australia

Crown fires are complex, unstable phenomena dependent on feedback mechanisms between the combustion products of distinct fuel layers. We describe non-linear fire behaviour associated with crowning and the uncertainty they cause in fire behaviour predictions by running a semiphysical modelling system within a simple Monte Carlo simulation framework. The method was able to capture the dynamics of passive and active crown fire spread regimes, providing estimates of average rate of spread and the extent of crown fire activity. System outputs were evaluated against data collected from a wildfire that occurred in a radiata pine plantation in south-eastern Australia. The Monte Carlo method reduced prediction errors relative to the more commonly used deterministic modelling approach, and allowed a more complete description of the level of crown fire behaviour to expect. The method also provides uncertainty measures and probabilistic outputs, extending the range of questions that can be answered by fire behaviour models.

Canopy bulk density and canopy base height equations for assessing crown fire hazard in Pinus radiata plantations

2011 ◽  
Vol 41 (4) ◽  
pp. 839-850 ◽  
Author(s):  
Ana Daría Ruiz-González ◽  
Juan Gabriel Álvarez-González
Keyword(s):  
Bulk Density ◽  
Pinus Radiata ◽  
Fire Hazard ◽  
Direct Action ◽  
Quantitative Information ◽  
Wildlife Habitat ◽  
Vertical Profiles ◽  
Crown Fire ◽  
Crown Fires ◽  
Canopy Bulk Density

Crown fires combine high rates of spread, flame lengths, and intensities, making it virtually impossible to control them by direct action and having significant impact on soils, vegetation, and wildlife habitat. For these reasons, fire managers have great interest in preventive silviculture of forested landscapes to avoid the initiation and propagation of crown fires. The minimum conditions necessary to initiate and propagate crown fires are assumed to be strongly influenced by the stand structural variables canopy bulk density (CBD) and canopy base height (CBH). However, there is a lack of quantitative information on these variables and how to estimate them. To characterize the aerial fuel layers of Pinus radiata D. Don, the vertical profiles of canopy fuel in 180 sample plots of pure and even-aged P. radiata plantations were analysed. Effective CBD and CBH were obtained from the vertical profiles, and equations relating these variables to common stand variables were fitted simultaneously. Inclusion of the fitted equations in existing dynamic growth models, together with the use of current fire behaviour and hazard prediction tools, will provide a decision support system for assessing the crown fire potential of different silvicultural alternatives for this species.

scholarly journals Evaluating the 3-m tree crown spacing guideline for the prevention of crowning wildfires in lodgepole pine forests, Alberta

2020 ◽  
Vol 96 (02) ◽  
pp. 165-173
Author(s):  
Martin E. Alexander ◽  
Miguel G. Cruz
Keyword(s):  
Bulk Density ◽  
Pinus Contorta ◽  
Lodgepole Pine ◽  
Pine Forests ◽  
Crown Fire ◽  
Conifer Forest ◽  
Fire Propagation ◽  
Current State ◽  
General Recommendation ◽  
Canopy Bulk Density

A 3-m between crown spacing is a commonly cited criterion found in the wildland-urban interface fire literature for minimizing the likelihood of a fully-developed crown fire from occurring in a conifer forest on level terrain. The validity of this general recommendation is examined here in light of our current state-of-knowledge regarding crown fire propagation in relation to canopy bulk density. Given the characteristics of the overstory structure for 20 lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) stands located in Alberta, as sourced from the literature, the canopy fuel properties following a virtual thinning to a 3-m crown spacing and then to a targeted canopy bulk density of 0.05 kg/m3 were computed. On the basis of these computations, crown fire potential was then analyzed and interpreted. The conclusion reached is that, in the majority of cases, a less widely spaced stand would be adequate for preventing crown fire development in lodgepole pine forests.

Development and testing of models for predicting crown fire rate of spread in conifer forest stands

2005 ◽  
Vol 35 (7) ◽  
pp. 1626-1639 ◽  
Author(s):  
Miguel G Cruz ◽  
Martin E Alexander ◽  
Ronald H Wakimoto
Keyword(s):  
Bulk Density ◽  
Fire Behavior ◽  
Fire Regimes ◽  
Management Decision ◽  
Crown Fire ◽  
Conifer Forest ◽  
Data Set ◽  
Rate Of Spread ◽  
Spread Model ◽  
Canopy Bulk Density

The rate of spread of crown fires advancing over level to gently undulating terrain was modeled through nonlinear regression analysis based on an experimental data set pertaining primarily to boreal forest fuel types. The data set covered a significant spectrum of fuel complex and fire behavior characteristics. Crown fire rate of spread was modeled separately for fires spreading in active and passive crown fire regimes. The active crown fire rate of spread model encompassing the effects of 10-m open wind speed, estimated fine fuel moisture content, and canopy bulk density explained 61% of the variability in the data set. Passive crown fire spread was modeled through a correction factor based on a criterion for active crowning related to canopy bulk density. The models were evaluated against independent data sets originating from experimental fires. The active crown fire rate of spread model predicted 42% of the independent experimental crown fire data with an error lower then 25% and a mean absolute percent error of 26%. While the models have some shortcomings and areas in need of improvement, they can be readily utilized in support of fire management decision making and other fire research studies.

Estimating canopy fuel characteristics for predicting crown fire potential in common forest types of the Atlantic Coastal Plain, USA

2018 ◽  
Vol 27 (11) ◽  
pp. 742 ◽  
Author(s):  
Anne G. Andreu ◽  
John I. Blake ◽  
Stanley J. Zarnoch
Keyword(s):  
Bulk Density ◽  
Coastal Plain ◽  
Canopy Cover ◽  
Atlantic Coastal Plain ◽  
Theoretic Approach ◽  
Crown Fire ◽  
Prescribed Burns ◽  
Stand Height ◽  
Atlantic Coastal ◽  
Canopy Bulk Density

We computed four stand-level canopy stratum variables important for crown fire modelling – canopy cover, stand height, canopy base height and canopy bulk density – from forest inventory data. We modelled the relationship between the canopy variables and a set of common inventory parameters – site index, stem density, basal area, stand age or stand height – and number of prescribed burns. We used a logistic model to estimate canopy cover, a linear model to estimate the other canopy variables, and the information theoretic approach for model selection. Coefficients of determination across five forest groups were 0.72–0.91 for stand height, 0.36–0.83 for canopy base height, 0.39–0.80 for canopy cover, and 0.63–0.78 for canopy bulk density. We assessed crown fire potential (1) for several sets of environmental conditions in all seasons, and (2) with increasing age, density and number of prescribed burns using our modelled canopy bulk density and canopy base height variables and local weather data to populate the Crown Fire Initiation and Spread model. Results indicated that passive crown fire is possible in any season in Atlantic coastal plain pine stands with heavy surface fuel loads and active crown fire is most probable in infrequently burned, dense stands at low fuel moistures.

Prescribed fire as a tool to regenerate live and dead serotinous jack pine (Pinus banksiana) stands

2017 ◽  
Vol 26 (6) ◽  
pp. 478 ◽  
Author(s):  
Maria Sharpe ◽  
Hyejin Hwang ◽  
David Schroeder ◽  
Soung Ryoul Ryu ◽  
Victor J. Lieffers
Keyword(s):  
Prescribed Fire ◽  
Natural Regeneration ◽  
Pinus Banksiana ◽  
Mountain Pine Beetle ◽  
Jack Pine ◽  
Crown Fire ◽  
Seedling Regeneration ◽  
Dead Trees ◽  
Crown Fires ◽  
Pine Beetle

This study documents cone opening and natural regeneration of jack pine (Pinus banksiana Lamb.) after burning live and dead stands similar to those killed by the mountain pine beetle (Dendroctonus ponderosae). Trees were killed by girdling in May and were burned in late July, 26 months later. Pairs of live and dead plots were simultaneously burned using three types of fire: surface, intermittent crown and continuous crown fires. Each type of fire was replicated three times; the nine pairs of burns were completed in a 4-day period. After fire, more cones were opened on dead trees than live trees. On dead trees, there was cone opening even when fire charred only the lower part of the bole. Three years after burning, dead stands with continuous crown fires had some of the densest regeneration and the highest rates of stocking. Across all burns in this study, seedling regeneration was best in shallow residual duff and in the more intensely burned plots. Without burning, there was virtually no regeneration 5 years after mortality. The results also show that burning, especially under continuous crown fire, could be used to promote regeneration in dead stands.

scholarly journals Daytime Heat Transfer Processes Related to Slope Flows and Turbulent Convection in an Idealized Mountain Valley

2010 ◽  
Vol 67 (11) ◽  
pp. 3739-3756 ◽  
Author(s):  
Stefano Serafin ◽  
Dino Zardi
Keyword(s):  
Heat Transfer ◽  
Ground Surface ◽  
Turbulent Convection ◽  
Mountain Valley ◽  
Transfer Processes ◽  
Slope Winds ◽  
Large Eddy ◽  
Thermally Driven ◽  
Slope Wind ◽  
The Impact

Abstract The mechanisms governing the daytime development of thermally driven circulations along the transverse axis of idealized two-dimensional valleys are investigated by means of large-eddy simulations. In particular, the impact of slope winds and turbulent convection on the heat transfer from the vicinity of the ground surface to the core of the valley atmosphere is examined. The interaction between top-down heating produced by compensating subsidence in the valley core and bottom-up heating due to turbulent convection is described. Finally, an evaluation of the depth of the atmospheric layer affected by the slope wind system is provided.

A Laboratory Investigation of Fire-Water Flooding

1974 ◽  
Vol 14 (06) ◽  
pp. 537-544 ◽  
Author(s):  
A.M. Garon ◽  
R.J. Wygal
Keyword(s):  
Heat Transfer ◽  
Combustion Zone ◽  
Enhanced Recovery ◽  
Water Injection ◽  
Systematic Investigation ◽  
Air Injection ◽  
Combustion Tube ◽  
Water Flooding ◽  
Transient Effects ◽  
Transfer Problems

Abstract The results of a systematic investigation of the parameters of fire-water flooding are reported. The parameters of fire-water flooding are reported. The results were obtained from a series of 131 combustion-tube tests. Experimental equipment and procedures were developed to minimize heat-transfer procedures were developed to minimize heat-transfer problems and transient effects at the inlet of the problems and transient effects at the inlet of the tube. The tests were performed with water/air injection ratios from 0 to 13 cu ft/Mscf, using crudes with gravities from 10 degrees to 48 degrees API, in waterflooded and nonwaterflooded sands at pressures of 0, 1,000, and 2,000 psig. The air requirements for fire-water flooding were reduced by more than 50 percent in some cases. Similar results were obtained with various crudes. Introduction The greater demand for crude oil, the increased difficulty of discovering new reservoirs, and the desire to reduce dependence on imports have emphasized the need for enhanced recovery methods capable of economically producing the crude remaining in known reservoirs. Numerous methods have been proposed and tested in laboratories and field pilots, and some have been used in commercial applications. Fire flooding is one enhanced recovery method that has been technically successful in many field applications. Some of these projects have been economically successful, but many are only marginally so. The high cost of air compression for fire flooding is one of the major factors that influence the economics. Large quantities of air are required per unit reservoir volume swept, especially for heavy crude, because all the residual material remaining in the sand immediately ahead of the combustion zone must be consumed. Only a portion of the heat generated is necessary for maintaining the movement of the combustion zone, and the remainder is left behind in the depleted sand. Fire-water flooding is a recovery technique that was conceived to improve the economics of dry fire flooding. In this process, water is injected along with the air to recover some of the heat remaining behind the combustion zone. At low water injection rates, the heat is transported through the combustion zone by superheated steam to where it can be utilized for preheating the reservoir. At higher water injection rates, the water partially quenches the combustion, reducing the maximum temperature to the steam-plateau level, and heat is transferred through the combustion zone as saturated steam. The air requirement is lower with water injection because the amount of hydrocarbonaceous material deposited on the sand grains is less and because all of this fuel is not necessarily consumed. At a constant air injection rate, the oil may be produced faster with water injection than without because of the more rapid combustion-zone movement, the increased utilization of energy, and the increased volume of fluid injected. Fire-water flooding has been investigated in several different laboratories with combustion-tube experiments. The feasibility of partially quenched combustion, the reduced air requirements, and the improved utilization of heat with water injection have been confirmed. However, the results of only a few experiments have been reported by each investigator, and only a limited amount of experimental information is available on the relationships of the fire-waterflooding parameters. in addition, it has been suggested that be results of wet combustion tests may be misleading because of experimental limitations. In this paper, the results of a systematic investigation of the parameters of fire-water flooding are reported. The results were obtained from combustion-tube tests. The equipment was designed to minimize heat-transfer problems, and operating procedures were developed that reduced the procedures were developed that reduced the transient effects at the inlet of the tube. SPEJ P. 537

scholarly journals Heat Balance of Horizontal Ground Heat Exchangers

2018 ◽  
Vol 25 (4) ◽  
pp. 537-548
Author(s):  
Krzysztof Kupiec ◽  
Monika Gwadera
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Ambient Temperature ◽  
Heat Balance ◽  
Heat Exchangers ◽  
Ground Surface ◽  
Temporal Variations ◽  
Moisture Evaporation ◽  
Ground Heat Exchangers

Abstract This work refers to the modelling of heat transfer in horizontal ground heat exchangers. For different conditions of collecting heat from the ground and different boundary condition profiles of temperature in the ground were found, and temporal variations of heat flux transferred between the ground surface and its interior were determined. It was taken into account that this flux results from several different mechanisms of heat transfer: convective, radiative, and that connected with moisture evaporation. It was calculated that ground temperature at great depths is greater than the average annual ambient temperature.

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