DETERMINING CONVECTIVE/RADIATIVE ENERGY PARTITIONING IN LARGE SCALE OPEN VEGETATION FIRES

“野火大测量挑战可以被描述为将火灾前和火灾后的测量和物理过程模型集成到一个强大且经过良好验证的框架中，用于表征耦合火灾-大气动力学，火灾排放，[…]]从火焰锋面到规定和野火事件的一系列尺度”（Kremens et al. 2010）。这个小型拨款项目的灵感来自于火灾研究界的“重大”挑战。特别是，火灾行为和火灾排放在很大程度上是由能量释放驱动的。了解火灾传播的能量平衡需要我们同时知道辐射热通量（RHF）和对流热通量（CHF），并将它们与燃烧燃料的总放热量（THR）联系起来。这是一项具有挑战性的任务，因为(i)从小规模实验室实验到露天植被火灾的火灾特性缩放程度是不确定的，（ii）由于羽流（CHF上的“可见”表现）通常是由环境风从其源作用（即火锋）平流出来的，因此不能通过单点测量将CHF和RHF联系起来。为了解决这些问题，我们需要制定一项协议，能够同时绘制大型室外“计划”火灾条件下的CHF和RHF。这种将燃料消耗的能量分配与各种热损失模式联系起来的综合数据集目前是不可用的，事实上，以前也没有进行过这样的测量。根据本项目的发起人及其同事在玻璃钢测量方案和通过航空热成像评估辐射热通量方面所做的工作，可以绘制植被火灾蔓延导致的RHF时空变化图。为了接近能量预算，我们需要(i)测量燃烧的燃料质量，以得出THR（可以通过火灾前和火灾后的原位采样轻松评估）和（ii）绘制CHF图，以便与RHF测量结果进行比较。因此，本提案的目的是开发实验测量方案和基础设施，能够同时记录植被火灾蔓延过程中辐射（RHF）和对流（CHF）热通量的时空变化，并将其部署在一系列实验烧伤中，以便为此类事件提供火灾能量分配的记录。该项目将与Martin Wooster教授领导的一个正在进行和一个新开始的项目相关联。特别是，NERC KE项目NE/J006432/1将与诺森伯兰郡消防和救援服务中心合作运行，将为未来几年英国计划发生的规定火灾提供许多开发、验证和部署方法的机会。据我们所知，这是第一次进行这样的实验，实验结果将提供给火灾科学界，供他们用于评估、改进和运行各种模拟模型。

"The wildland fire grand measurement challenge can be described as the integration of pre- active- and post-fire measurements and physical process models into a robust and well validated framework for characterizing coupled fire-atmosphere dynamics, fire emissions, [...] at a range of scales from flame fronts to prescribed and wildfire events" (Kremens et al. 2010). This small grant project is inspired by this "grand" challenge of the fire research community. In particular, fire behavior and fire emissions are largely driven by energy releases. Understanding the energy budget of a propagating fire requires us to know simultaneously both the Radiative Heat Fluxes (RHF) and Convective Heat Fluxes (CHF), and to relate them to the total heat release (THR) of the combusted fuel. This is a challenging task because (i) the degree to which scaling of fire properties from small scale lab experiments to open vegetation fires can be performed is uncertain, and (ii) CHF and RHF cannot be linked by single point measurement since the plume (the 'visible' manifestation on the CHF) is usually advected from its source action (i.e. the fire front) by the ambient wind. To tackle these issues, we need to develop a protocol able to map simultaneously CHF and RHF under the conditions present in large outdoor "planned" fires.Such comprehensive sets of data linking energy partitioning from fuel consumption with the various modes of heat loss are unavailable currently, and indeed such measurements have not been conducted before. According to the work realised by the proposers of this project and co-workers on FRP measurement protocols and radiative heat flux assessment via airborne thermal imagery, spatio-temporal variations of the RHF from spreading vegetation fires can however be mapped. To close the energy budget, we then need (i) to measure the fuel mass burnt to derive THR (which can be easily assessed with pre- and post- fire in situ sampling) and (ii) to map CHF to allow comparison with the RHF measure.The aim of this proposal is therefore to develop the experimental measurement protocol and infrastructure capable of recording simultaneously the temporal and spatial variability of radiative (RHF) and convective (CHF) heat fluxes in spreading vegetation fires, and to deploy this at a series of experimental burns in order to deliver a record of fire energy partitioning for such events. This project will link to one ongoing and one newly commencing projects lead by Prof Martin Wooster. In particular, NERC KE project NE/J006432/1 that will run in collaboration with the Northumberland Fire and Rescue Service will provide many opportunities to develop, validate, and deploy the methodology at prescribed fires planned to occur in the UK over the next few years. To our knowledge this is the first time that such an experiment will be conducted, and the results will be made available to the fire science community for their use in the evaluation, improvement and running of a variety of simulation models.