Abstract

Fire accidents are more likely to occur in tunnels with different curves, aspect ratios, and slopes due to the land’s geographical characteristics. A three-dimensional computational fluid dynamics code with curvilinear grids fitted to the body was used to simulate a variety of fire locations releasing heat at a rate of 5 MW–60 MW in a tunnel with a turning radius of 100 m–1500 m, an aspect ratio of 0.5–2, and a slope between – 10% and 10%. Using the Design of Experiments (DOE) method coupled with numerical simulations, 32 3D numerical models were constructed and a second-order critical velocity model was generated. Analysis of critical velocity was performed based on Response Surface Methodology (RSM) and multifactor curve plots were drawn for effective parameters. The results showed that the critical velocity was proportional to one-third power of the heat release rate. It was also observed that the critical velocity increased gradually as the fire source moved from the tunnel’s center to its walls. Furthermore, the critical velocity decreased with increasing the aspect ratio. Results showed that the critical velocity increased with increasing the tunnel turning radius. Moreover, tunnels with negative slopes have a higher critical velocity than horizontal tunnels without slopes. Finally, by defining the parameters in non-dimensional form, a new modified form was derived for critical velocity calculation (R² = 0.98). A critical velocity of 1.24 m/s–5.21 m/s was calculated based on five parameter values in this study. Furthermore, other straight and curved tunnel models confirmed the formula’s predictions.

中文翻译：

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弯曲隧道火灾参数对临界速度的影响：数值研究和响应面分析

摘要

由于土地的地理特征，不同曲线、高宽比、坡度的隧道更容易发生火灾事故。使用安装在主体上的曲线网格的三维计算流体动力学代码来模拟在转弯半径为 100 m–1500 m 的隧道中以 5 MW–60 MW 的速率释放热量的各种火灾位置，纵横比为 0.5-2，坡度为 – 10% 至 10%。采用实验设计 (DOE) 方法与数值模拟相结合，构建了 32 个 3D 数值模型，并生成了二阶临界速度模型。基于响应面法（RSM）对临界速度进行分析，绘制有效参数的多因素曲线图。结果表明，临界速度与放热率的三分之一次方成正比。还观察到，随着火源从隧道中心移动到墙壁，临界速度逐渐增加。此外，临界速度随着纵横比的增加而降低。结果表明，临界速度随着隧道转弯半径的增大而增大。此外，负坡度隧道比没有坡度的水平隧道具有更高的临界速度。最后，通过无量纲形式定义参数，导出了临界速度计算的新修正形式（R ² = 0.98）。本研究根据五个参数值计算出临界速度为1.24 m/s~5.21 m/s。此外，其他直线和曲线隧道模型也证实了该公式的预测。