Compression driven shock tubes are indispensable in studies of blast-induced traumatic brain injury (bTBI). The ability of shock tubes in faithfully recreating free-field blast conditions is of enormous interest and has a direct impact on injury outcomes. Toward this end, the evolution of blast wave inside and outside of the compression driven shock tube has been studied using validated, finite element based shock tube models. Several shock tube configurations (uniform cross-section, transition, conical, suddenly expanded, and end plate) have been considered. The finite element modeling approach has been used to simulate the transient, dynamic response of blast wave propagation. The response is studied for longer durations (40–100 msec) compared with the existing literature. We demonstrate that locations inside and outside of the shock tube can generate free-field blast profile in some form, but with numerous caveats. Our results indicate that the locations inside the shock tube are affected by higher underpressure and corresponding kinetic energy yield compared with free-field blast. These effects can be minimized using optimized end plate configuration at the exit of the shock tube, yet this is accompanied by secondary loading that is not representative of the free-field blast. Blast wave profile can be tailored using transition, conical, and suddenly expanded sections. We observe oscillations in the blast wave profile for suddenly expanded configuration. Locations outside the shock tube are affected by jet-wind effects because of the sudden expansion, barring a narrow region at the exit. For the desired overpressure yield inferred in bTBI, obtaining positive phase durations of <1 msec inside the shock tube, which are sought for studies in rodents, is challenging. Overall, these results underscore that replicating free-field blast conditions using a shock tube involves tradeoffs that need to be weighed carefully and their effect on injury outcomes should be evaluated during laboratory bTBI investigations.

中文翻译：

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评估压缩驱动冲击管设计在创伤性脑损伤研究中复制自由场爆炸条件中的作用

压缩驱动的冲击管在爆炸性外伤性脑损伤 (bTBI) 的研究中是必不可少的。激波管忠实地再现自由场爆炸条件的能力引起了人们极大的兴趣，并且对伤害结果有直接影响。为此，已经使用经过验证的基于有限元的激波管模型研究了压缩驱动激波管内部和外部的冲击波演变。已经考虑了几种激波管配置（均匀截面、过渡、锥形、突然膨胀和端板）。有限元建模方法已被用于模拟冲击波传播的瞬态动态响应。与现有文献相比，该响应的研究时间更长（40-100 毫秒）。我们证明了冲击管内部和外部的位置可以以某种形式产生自由场爆炸剖面，但有许多警告。我们的结果表明，与自由场爆炸相比，激波管内的位置受到更高的负压和相应的动能产量的影响。在激波管出口处使用优化的端板配置可以最大限度地减少这些影响，但这伴随着二次载荷，这并不代表自由场爆炸。可以使用过渡、锥形和突然扩展的部分来定制冲击波轮廓。我们观察到冲击波剖面中突然扩展配置的振荡。由于突然膨胀，激波管外部的位置受到喷射风效应的影响，出口处的狭窄区域除外。对于在 bTBI 中推断出的所需超压产率，在用于啮齿动物研究的冲击管内获得 <1 毫秒的正相持续时间是具有挑战性的。总体而言，这些结果强调了使用冲击管复制自由场爆炸条件涉及需要仔细权衡的权衡，并且应在实验室 bTBI 调查期间评估其对损伤结果的影响。