Large eddy simulation of atypical wildland fire spread on leeward slopes
Large eddy simulation of atypical wildland fire spread on leeward slopes
复制标题
DOI：
10.1071/wf12072
复制
发表时间：
2013-01-01
影响因子：
3.1
通讯作者：
McCabe, Matthew F.
中科院分区：
文献类型：
--
作者：
Simpson, Colin C.;Sharples, Jason J.;McCabe, Matthew F.
通过一系列理想化的数值模拟，使用WRF - Fire大气 - 火灾耦合模拟系统研究了在陡峭背风坡上非典型的野外火灾蔓延情况。这些模拟用于研究背风流的特性，比如气流分离，以及从背风坡底部着火区域开始的火灾蔓延。考虑了不同燃料类型以及启用和禁用大气 - 火灾耦合情况下的火灾蔓延。当启用大气 - 火灾耦合且燃料质量密度较高时，火灾蔓延与火灾通道效应预期的情况非常相似。具体来说，火灾最初以平均2.0千米/小时的速度沿山坡向上蔓延至山脊线，随后主要在山脊线附近以最大3.6千米/小时的速度横向蔓延。当中尺度对流上升 - 下沉气流界面（其与火焰中部高度处强烈循环的水平风有关）移动穿过山脊线附近的火场周边时，会出现间歇性的快速横向蔓延。中尺度对流上升 - 下沉气流界面是由于强烈的火对流与地形改变的风之间的相互作用而形成的。通过这些结果，提出了一种关于火灾通道效应的新的物理解释。
The WRF-Fire coupled atmosphere-fire modelling system was used to investigate atypical wildland fire spread on steep leeward slopes through a series of idealised numerical simulations. The simulations are used to investigate both the leeward flow characteristics, such as flow separation, and the fire spread from an ignition region at the base of the leeward slope. The fire spread was considered under varying fuel type and with atmosphere-fire coupling both enabled and disabled. When atmosphere-fire coupling is enabled and there is a high fuel mass density, the fire spread closely resembles that expected during fire channelling. Specifically, the fire spread is initially dominated by upslope spread to the mountain ridge line at an average rate of 2.0 km h(-1), followed by predominantly lateral spread close to the ridge line at a maximum rate of 3.6 km h(-1). The intermittent rapid lateral spread occurs when updraft-downdraft interfaces, which are associated with strongly circulating horizontal winds at the mid-flame height, move across the fire perimeter close to the ridge line. The updraft-downdraft interfaces are formed due to an interaction between the strong pyro-convection and the terrain-modified winds. Through these results, a new physical explanation of fire channelling is proposed.