Reconstruction of fire whirls using scale models
Reconstruction of fire whirls using scale models
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DOI：
10.1016/0010-2180(91)90107-m
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发表时间：
1991-08
影响因子：
4.4
通讯作者：
S. Soma;Kozo Saito
中科院分区：
文献类型：
--
作者：
S. Soma;Kozo Saito
这项工作的动机是了解历史上的一场火旋风事故，其中一场火旋风造成38，000人死亡和对环境的严重破坏，所有这些都发生在15分钟内。为了了解火旋风的一般特征，收集了示例火旋风的记录，并将其归纳为三种不同类型。采用量纲分析法推导出了三种不同比例的模型，其比例分别为1 235、1 2500和1 4837，对应于三个实际的火旋风（原型）。以甲醇为火源，通过改变风速进行了风洞火灾实验，以了解火旋风发生的条件。在实验室重建的模型火旋风可视化与水蒸气和速度和温度的分布，分别由热线风速计和精细热电偶测量。由于原型火旋风的动力学结构在实际流场中缺乏直接的测量结果，因此设计了一个与原型火旋风缩尺比为1 100的大比例尺模型进行了野外试验研究。该模型由85个圆形平底锅填充有2.3米3的甲醇，分布在400平方米的区域。彩色烟雾使空气流动可视化。在五个不同的地点测量了风速和风向，在九个不同的地点测量了气温。结果发现，可视化确定的旋流直径和旋流柱高度，和最大切向速度的旋流可以相关的1 2500缩尺模型的建议的比例尺律。
This work was motivated from the knowledge of a historical fire whirl accident in which a fire whirl was responsible for 38,000 deaths and serious damage to the environment, all of which happened within 15 minutes. To understand the general features of fire whirls, records of example fire whirls were collected and deduced to be of three different types. Scaling laws were derived using dimensional analysis; three types of scale-models, with scaling ratios of 1 235, 1 2500, and 1 4837, corresponding to three actual fire whirls (prototypes), were designed in the laboratory. Wind tunnel fire experiments were performed burning methanol as the fire source and by changing the wind velocity to understand conditions under which fire whirls can occur. The model fire whirls reconstructed in the laboratory were visualized with water vapor; and profiles of velocity and temperature were, respectively, measured by a hot wire anemometer and a fine thermocouple. Because the dynamic structure of prototype fire whirls is not known due to lack of direct measurements in actual flows, a large scale-model with scaling ratio of 1 100 to the prototype was designed to be studied in an open field. This model consisted of 85 circular pans filled with 2.3 m 3 of methanol that were distributed in an area of 400 m 2. Air movement was visualized by colored smoke. Wind velocity and direction were measured at five different locations and air temperatures at nine different locations. It was found that the visually determined whirl diameter and whirl column height, and the maximum tangential velocity of the whirl can be correlated to the 1 2500 scale model by the proposed scaling laws.