| The forest-fire not only brings massive loss to the country and people's properties, destructing the ecosysterm,reducing the soil fertility, but also causes some natural disasters as water and soil erosion,mud-rock flow and so on.Research on forest-fire spread simulation can effectively reduce the loss of disasters. The forest-fire behavior's expansion has the characteristics of timeliness and space and with strong randomness. The research under different environment's forest-fire spread situation and trend of development together with the visualization spread process is the research tendency concerned with making the most superior fire-fighting plan and enhancing fire-fighting efficiency, which is also the this research focus of this article. This task is based on the significant scientific projects of Guangzhou-----Guangzhou's Forest-Fire Prevention Information System (Serial No.200201) which is an important research module in the subsystem of fire fighting forest fire.This article has consulted massive domestic and foreign literatures and generally analyzed domestic and foreign forest-fire spread research development and relative factors of influencing the forest-fire spread, summarizing the principles,parameter' s gain,construction and solution of Rothermel spread model condition systematically and comprehensively. Guided by computer graphics,forest-fire science,combustion theory and combined with computer simulation technology,geographic information system and mathematical model technology, choosing trial forest land to carry on the model construction,solving and visualization.The main research results are as follows:(1)Through analyzing the research development of domestic and foreign forest-fire model technology, on the basis of contrastive analysis to these technology's good and bad points and the research trend of development and its applicable scope, along with combining with the trial forest land's actual situation, having confirmed that using the Rothermel spread model to carry on forest-fire spread simulation of trial forest land is feasible.(2)The article has established a set of technology frame which is on model parameter extraction processing according to analysis of the construction principles of the forest-fire behavior and the spread model from the angle of forest-fire's mechanism of combustion.On the foundation of analyzing the factors of influencing the forest-fire spread speed, adopting the Rothermel surface-fire spread model as the frame, in view of Panyu District's characteristics in Guangdong Province, finding out each parameter's value through the domestic and foreign literatures and in-the-spot investigation, stock-map and other materials.Among which the parameters obtained by computation or in-the-spot measurement including the combustion bed depth of combustible substance, forest-fire extinguishment moisture rate of dead combustible substance, each level's load capacity of drying combustible substance,the surface area and volume ratio, moisture content, slope, aspect, wind speed and direction. Other parameters like low enthalpy, drying grain density, total mineral substance content, effective mineral substance content which are all obtained the empirical value through consulting literatures.(3)Based on labyrinth algorithm's spread proliferation principle, we realize the mathematical model construction of forest-fire spread process and obtaining the burned process of forest-fire.(4)We can obtain the behavioral indicator of forest-fire spread and that a more complete and intuitionistic situation of forest-fire spread is embodied in it by the way of computing forest-fire's livewire intensity,the height of flames,the temperature of livewire zone and its area,perimeter.(5)To summarize the above technical solutions, it has developed the corresponding dynamic module established in the VBA platform to accomplish the visualization of spread result by systematic analysis,module design,system integration and has given a typical application instance.(6)Through the result precision verification,we proved that applying the labyrinth algorithm and Rothermel spread model to carry on the forest-fire spread simulation can achieve the goal of model forecast and can reflect the main rules of forest-fire spread. In contrasts to simulated results of the two trial forest lands, it has intuitionisticly manifested the influences to forest-fire spread which were brought about by moisture content, the wind speed, the length of stride and the surface area or the volume ratio and some other dynamic factors. The forest-fire spread is an extremely complex phenomenon that heterogeneity and multi-component combustible substance can burn and move under various meteorological conditions and terrain influences.It has been restricted by all kinds of uncertainties in natural environment such as that real-time change of wind speed and the jump fire,fire tornado,flashover and other complex natural phenomena which were brought by air-current change.Subsequently, the research on forest-fire spread simulation is also a long-term and arduous work. With the correlation unceasing progress of techniques, the accuracy and timeliness of forest-fire spread simulation will be getting stronger and stronger, but it still shoulders heavy responsibilities to establish a forest-fire spread simulation system.
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