无人机视角下的林木爆燃火特性研究

森林火灾“爆燃”现象的特征是突然发生的高强度、高蔓延速度的燃烧。目前为止，关于“爆燃火”的原因还没有达成共识。以无人机视角下对林木爆燃火特性研究，以四川木里特大森林火灾为研究对象，通过分析凉山州某森林扑火部队3月31日木里森林火灾当天KWT（科卫泰）无人机航拍火场画面，结合无人机实时影像及实地调研数据，分析了峡谷地形林火蔓延时空特征，探讨了峡谷中风向风速变化时空分布规律，研究了地形变化条件下，不同海拔高度风速特征，建立了无人机倾角测量风速模型（其中为风速m·s-1，为无人机倾角°）。结果表明，高山峻岭特殊地形环境下每天4:00—12:00时间段为静风期，为峡谷林火扑救最佳时期；午后15:00—17:00和晚上20:00—22:00为山谷地形风速活跃期；仿真软件数据显示山顶、谷底与山腰不同海拔位置的风速风向不统一，谷底会产生乱流现象，且风速与海拔不存在正相关关系，小气候在复杂地形中占主导影响地位；在谷口至山谷深处的中间位置会出现气流速度的波峰状态，并易形成乱流，为爆燃火发生提供了客观必要条件。该研究可为复杂地形环境下，森林草原火灾扑救安全提供数据和技术支撑。

Deflagration Characteristics of Forest Trees from the Perspective of UAV

The phenomenon of “deflagration” in forest fires is characterized by a sudden occurrence of high-intensity combustion with high spreading speed. Consensus hasn’t been reached about the causes of “detonation fire” so far. In this study, forest fire videos, real-time pose data, and wind speed estimation derived from KWT (Keweitai) drone, together with field research data were analyzed to characterize the spatial and temporal feature of forest fire spreading within a valley topography in Liangshan Prefecture, which killed 27 firefighters on 31 March 2019. We found that: the microclimate played a dominant role in complex terrain, and the special period of the high mountain terrain was 4:00—12:00 every day for the quiet wind period, which was the best period for the canyon forest fire fighting. The wind speed of the valley topography was active from 15:00—17:00 in the afternoon and from 20:00—22:00 in the evening, the model of relationship between inclination angle of the drone and wind speed was established y=-1.043 5+1.150 1x(y is the wind speed m·s-1, and x is the uav inclination °) . The wind speed and direction of the mountain, valley and mountainside were not uniform, and there was no positive correlation between wind speed and altitude. The peak state of the airflow velocity occurred in the middle of the valley to the depth of the valley, and there would be turbulent flow at the bottom of the valley, which provides objective and necessary conditions for the occurrence of deflagration fire. The short duration of drones was the bottleneck of forest fire monitoring.