This paper presents an analysis of the fire trends in southern European countries, where forest fires are a major hazard. Data on number of fires and burned area size from 1985 until 2009 were retrieved from the Europ...This paper presents an analysis of the fire trends in southern European countries, where forest fires are a major hazard. Data on number of fires and burned area size from 1985 until 2009 were retrieved from the European Fire Database in the European Forest Fire Information System and used to study the temporal and spatial variability of fire occurrence at three different spatial scales： the whole European Mediterranean region, country level and province level （NUTS3）. The temporal trends were assessed with the Mann-Kendall test and Sen＇s slope in the period 1985-2009. At regional （supranational） level, our results suggest a significant decreasing trend in the burned area for the whole study period. At country level, the trends vary by country, although there is a general increase in number of fires, mainly in Portugal, and a decrease in bumed areas, as is the case of Spain. A similar behavior was found at NUTS3 level, with an increase of number of fires in the Spanish and Portuguese provinces and a generalized decrease of the burned area in most provinces of the region. These results provide an important insight into the spatial distribution and temporal evolution of fires, a crucial step to investigate the underlying causes and impacts of fire occurrence in this region.展开更多
The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for this particular ca...The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for this particular case of fire propagation. The test of this proposed model was performed by using two complete sets of experimental results with several fuel beds and variable parameters such as moisture content or bulk density. The second aim of this article is to highlight two conditions that allow stopping a fire： the low leaf area and the high value of the moisture content.展开更多
In Australia,the proportion of forest area that burns in a typical fire season is less than for other vegetation types.However,the 2019-2020 austral spring-summer was an exception,with over four times the previous max...In Australia,the proportion of forest area that burns in a typical fire season is less than for other vegetation types.However,the 2019-2020 austral spring-summer was an exception,with over four times the previous maximum area burnt in southeast Australian temperate forests.Temperate forest fires have extensive socio-economic,human health,greenhouse gas emissions,and biodiversity impacts due to high fire intensities.A robust model that identifies driving factors of forest fires and relates impact thresholds to fire activity at regional scales would help land managers and fire-fighting agencies prepare for potentially hazardous fire in Australia.Here,we developed a machine-learning diagnostic model to quantify nonlinear relationships between monthly burnt area and biophysical factors in southeast Australian forests for 2001-2020 on a 0.25°grid based on several biophysical parameters,notably fire weather and vegetation productivity.Our model explained over 80%of the variation in the burnt area.We identified that burnt area dynamics in southeast Australian forest were primarily controlled by extreme fire weather,which mainly linked to fluctuations in the Southern Annular Mode(SAM)and Indian Ocean Dipole(IOD),with a relatively smaller contribution from the central Pacific El Niño Southern Oscillation(ENSO).Our fire diagnostic model and the non-linear relationships between burnt area and environmental covariates can provide useful guidance to decision-makers who manage preparations for an upcoming fire season,and model developers working on improved early warning systems for forest fires.展开更多
Turbulent reacting flows in a generic swirl gas turbine combustor model are investigated both numerically and experimentally.In the investigation,an emphasis is placed upon the external flue gas recirculation,which is...Turbulent reacting flows in a generic swirl gas turbine combustor model are investigated both numerically and experimentally.In the investigation,an emphasis is placed upon the external flue gas recirculation,which is a promising technology for increasing the efficiency of the carbon capture and storage process,which,however,can change the combustion behaviour significantly.A further emphasis is placed upon the investigation of alternative fuels such as biogas and syngas in comparison to the conventional natural gas.Flames are also investigated numerically using the open source CFD software OpenFOAM.In the numerical simulations,a laminar flamelet model based on mixture fraction and reaction progress variable is adopted.As turbulence model,the SST model is used within a URANS concept.Computational results are compared with the experimental data,where a fair agreement is observed.展开更多
文摘This paper presents an analysis of the fire trends in southern European countries, where forest fires are a major hazard. Data on number of fires and burned area size from 1985 until 2009 were retrieved from the European Fire Database in the European Forest Fire Information System and used to study the temporal and spatial variability of fire occurrence at three different spatial scales： the whole European Mediterranean region, country level and province level （NUTS3）. The temporal trends were assessed with the Mann-Kendall test and Sen＇s slope in the period 1985-2009. At regional （supranational） level, our results suggest a significant decreasing trend in the burned area for the whole study period. At country level, the trends vary by country, although there is a general increase in number of fires, mainly in Portugal, and a decrease in bumed areas, as is the case of Spain. A similar behavior was found at NUTS3 level, with an increase of number of fires in the Spanish and Portuguese provinces and a generalized decrease of the burned area in most provinces of the region. These results provide an important insight into the spatial distribution and temporal evolution of fires, a crucial step to investigate the underlying causes and impacts of fire occurrence in this region.
文摘The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for this particular case of fire propagation. The test of this proposed model was performed by using two complete sets of experimental results with several fuel beds and variable parameters such as moisture content or bulk density. The second aim of this article is to highlight two conditions that allow stopping a fire： the low leaf area and the high value of the moisture content.
基金supported by the National Natural Science Foundation of China(42088101 and 42030605)support from the research project:Towards an Operational Fire Early Warning System for Indonesia(TOFEWSI)+1 种基金The TOFEWSI project was funded from October 2017-October 2021 through the UK’s National Environment Research Council/Newton Fund on behalf of the UK Research&Innovation(NE/P014801/1)(UK Principal InvestigatorAllan Spessa)(https//tofewsi.github.io/)financial support from the Natural Science Foundation of Qinghai(2021-HZ-811)。
文摘In Australia,the proportion of forest area that burns in a typical fire season is less than for other vegetation types.However,the 2019-2020 austral spring-summer was an exception,with over four times the previous maximum area burnt in southeast Australian temperate forests.Temperate forest fires have extensive socio-economic,human health,greenhouse gas emissions,and biodiversity impacts due to high fire intensities.A robust model that identifies driving factors of forest fires and relates impact thresholds to fire activity at regional scales would help land managers and fire-fighting agencies prepare for potentially hazardous fire in Australia.Here,we developed a machine-learning diagnostic model to quantify nonlinear relationships between monthly burnt area and biophysical factors in southeast Australian forests for 2001-2020 on a 0.25°grid based on several biophysical parameters,notably fire weather and vegetation productivity.Our model explained over 80%of the variation in the burnt area.We identified that burnt area dynamics in southeast Australian forest were primarily controlled by extreme fire weather,which mainly linked to fluctuations in the Southern Annular Mode(SAM)and Indian Ocean Dipole(IOD),with a relatively smaller contribution from the central Pacific El Niño Southern Oscillation(ENSO).Our fire diagnostic model and the non-linear relationships between burnt area and environmental covariates can provide useful guidance to decision-makers who manage preparations for an upcoming fire season,and model developers working on improved early warning systems for forest fires.
文摘Turbulent reacting flows in a generic swirl gas turbine combustor model are investigated both numerically and experimentally.In the investigation,an emphasis is placed upon the external flue gas recirculation,which is a promising technology for increasing the efficiency of the carbon capture and storage process,which,however,can change the combustion behaviour significantly.A further emphasis is placed upon the investigation of alternative fuels such as biogas and syngas in comparison to the conventional natural gas.Flames are also investigated numerically using the open source CFD software OpenFOAM.In the numerical simulations,a laminar flamelet model based on mixture fraction and reaction progress variable is adopted.As turbulence model,the SST model is used within a URANS concept.Computational results are compared with the experimental data,where a fair agreement is observed.
