上山火加速过程的模拟计算与实验研究

Study on Experiment and Simulation of Forest Fire Spread in a Mountain Slope

通过对林火蔓延过程的理论分析 ,建立了模拟林火进入斜坡后的计算模型 ,采用数值法计算了林火在斜坡上蔓延的加速度以及初期蔓延过程。同时 ,在燃料床上进行模拟实验 ,测取了林火自水平燃料床进入倾斜燃料床后的火蔓延速度和加速度。通过对理论计算与实验结果的比较 ,说明理论模型是合理的。由实验与理论分析可知 ,森林火灾一旦蔓延进入山坡之后 ,在大约 1到 2 min之内 ,火蔓延的加速度很快达到最大值 ,随着坡度的增加 ,火蔓延加速度达到最大值所需要的时间减少。达最大值之后 ,加速度逐渐减小 ,直到稳定的蔓延速度。同时发现 ,林火进入斜坡之后 ,大约需要 2 5 min才能达到稳定的蔓延速度 ,这个结论是通过计算得到的 。

WT5”BZ]A model of fire spread on the slope was constructed through theoretical analysis.The acceleration and the rate of fire spread were numerically calculated.The process of fire spread from the lowest point of a slope to the maximum acceleration instant was simulated in a fuel bed.By comparing the calculated data with the experiment results,we find that the theoretical model is reasonable.According to the theoretical analysis and experimental results,when the forest fire enters a mountain slope from a plain,the acceleration of fire spread reaches its maximum in 1 or 2 minutes,then the acceleration begins to wane.After 25 minutes,the rate of fire spread can reach its steady data.As the slope angle increases,the time of getting steady rate of fire spread and maximum acceleration are reduced.Because a long fuel bed and time are needed to simulate the steady fire spread,it is impossible to simulate this process in the laboratory. [WT5”HZ]