Physics-Based Simulation of Heat Load on Structures for Improving Construction Standards for Bushfire Prone Areas

IF 2 Q2 ENGINEERING, MECHANICAL
Nazmul Khan, D. Sutherland, R. Wadhwani, K. Moinuddin
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引用次数: 12

Abstract

Australian building standard AS 3959 provides mandatory requirements for the construction of buildings in bushfire prone areas in order to improve the resilience of the building to radiant heat, flame contact, burning embers, and a combination of these three bushfire attack forms. The construction requirements are standardised based on the bushfire attack level (BAL). BAL is based on empirical models which account for radiation heat load on structure. The prediction of the heat load on structure is a challenging task due to many influencing factors: weather conditions, moisture content, vegetation types and fuel loads. Moreover, the fire characteristics change dramatically with wind velocity leading to buoyancy or wind dominated fires that have different dominant heat transfer processes driving the propagation of the fire. The AS 3959 standard is developed with respect to a quasi-steady state model for bushfire propagation assuming a long straight line fire. The fundamental assumptions of the standard are not always valid in a bushfire propagation. In this study, physics based large-eddy simulations were conducted to estimate the heat load on a model structure. The simulation results are compared to the AS 3959 model; there is agreement between the model and the simulation, however, due to computational restrictions the simulations were conducted in a much narrower domain. Further simulations were conducted where wind velocity, fuel load, and relative humidity are varied independently and the simulated radiant heat flux upon the structure was found to be significantly greater than predicted by the AS 3959 model. The effect of the mode of fire propagation, either buoyancy-driven or wind dominated fires, is also investigated. For buoyancy dominated fires the radiation heat load on the structure is enhanced compared to the wind dominated fires. Finally, the potential of using physics based simulation to evaluate individual designs is discussed.
基于物理的结构热负荷模拟提高森林火灾易发地区建筑标准
澳大利亚建筑标准AS 3959为森林火灾易发地区的建筑提供了强制性要求,以提高建筑物对辐射热、火焰接触、燃烧余烬以及这三种森林火灾攻击形式的组合的恢复能力。建筑要求是根据森林火灾攻击等级(BAL)进行标准化的。BAL基于考虑结构辐射热负荷的经验模型。由于天气条件、水分含量、植被类型和燃料负荷等因素的影响,结构热负荷的预测是一项具有挑战性的任务。此外,火灾特征随风速变化显著,导致浮力或风主导火灾,它们具有不同的主导传热过程驱动火灾的传播。AS 3959标准是针对假定长直线火灾的森林火灾传播的准稳态模型而制定的。标准的基本假设在森林火灾传播中并不总是有效的。在本研究中,采用基于物理的大涡模拟来估计模型结构的热负荷。仿真结果与AS 3959模型进行了比较;模型与仿真结果是一致的,但由于计算的限制,模拟的范围要窄得多。在风速、燃料负荷和相对湿度独立变化的情况下进行了进一步的模拟,发现模拟的结构辐射热通量明显大于AS 3959模型的预测值。此外,还研究了浮力驱动或风力主导的火灾传播方式的影响。对于浮力主导的火灾,结构的辐射热负荷比风主导的火灾增强。最后,讨论了使用基于物理的仿真来评估单个设计的潜力。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Frontiers in Mechanical Engineering
Frontiers in Mechanical Engineering Engineering-Industrial and Manufacturing Engineering
CiteScore
4.40
自引率
0.00%
发文量
115
审稿时长
14 weeks
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