Experimental investigation of blast mitigation of pre-fractal obstacles
Experimental investigation of blast mitigation of pre-fractal obstacles
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DOI：
10.1177/20414196221144066
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发表时间：
2022-12
影响因子：
2
通讯作者：
Obed Samuelraj Isaac;Omar Ghareeb Alshammari;S. Clarke;S. Rigby
中科院分区：
文献类型：
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作者：
Obed Samuelraj Isaac;Omar Ghareeb Alshammari;S. Clarke;S. Rigby
采用250 g PE4在三种不同的比例距离（Z = 1.87、2.24、2.99 m/kg1/3）下测试了障碍物布置成预分形（Sierpinski地毯）的爆炸衰减能力。测试了三个预分形迭代，以及用于比较目的的自由场测试。由于一种被称为“捕获”的机制，峰值超压降低了26%，峰值比冲降低了19%。这种机制的特点是爆炸波向下游平流的能力降低，在分形前障碍的范围内观察到相应的压力增加。在每次预分形迭代中，衰减幅度和减少的压力和脉冲面积都有很大的不同，随着障碍物更接近真实的分形，从阴影到波捕获的过渡。到达时间、超压和脉冲与新定义的障碍物因子（OF）呈线性关系，表明前分形障碍物的衰减本质上是可确定的。研究结果表明，预分形障碍物的爆破缓解机制与单一或排列规则障碍物有本质区别，可以进一步开发具有增强爆破衰减的新型防护结构。
Obstacles arranged into a pre-fractal shape (Sierpinski carpet) were tested for their blast attenuation abilities using 250 g PE4 at three different scaled distances (Z = 1.87, 2.24, 2.99 m/kg1/3). Three pre-fractal iterations were tested, as well as free-field tests for comparative purposes. Reductions in peak overpressure up to 26% and peak specific impulse up to 19% were observed, attributed to a mechanism known as ‘trapping’. This mechanism is characterised by a reduction in the ability of a blast wave to advect downstream, with corresponding increases in pressure observed within the bounds of the pre-fractal obstacle. Attenuation magnitudes and areas of reduced pressure and impulse were found to be drastically different with each pre-fractal iteration, with a transition from shadowing to wave trapping as the obstacles more closely resembled true fractals. A linear dependence on a newly-defined obstruction factor (OF) was found for arrival time, overpressure and impulse at the sensor locations, suggesting that the attenuation of a pre-fractal obstacle is inherently determinable. The results indicate that the mechanism of blast mitigation of pre-fractal obstacles is fundamentally different from singular or arrays of regular obstacles, and could be exploited further to develop novel protective structures with enhanced blast attenuation.