Sutar Sunil, Ganpule S G
Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, Roorkee, India.
J Neurotrauma. 2021 Jun 15;38(12):1717-1729. doi: 10.1089/neu.2020.7394. Epub 2021 Jan 15.
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.
压缩驱动激波管在爆炸诱导的创伤性脑损伤（bTBI）研究中不可或缺。激波管忠实地再现自由场爆炸条件的能力备受关注，并且对损伤结果有直接影响。为此，已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外爆炸波的演变。考虑了几种激波管配置（均匀横截面、过渡段、锥形、突然扩张和端板）。有限元建模方法已用于模拟爆炸波传播的瞬态动态响应。与现有文献相比，对更长持续时间（40 - 100毫秒）的响应进行了研究。我们证明，激波管内外的位置可以以某种形式产生自由场爆炸轮廓，但存在许多注意事项。我们的结果表明，与自由场爆炸相比，激波管内部的位置受到更高负压和相应动能产量的影响。使用激波管出口处优化的端板配置可以将这些影响最小化，但这伴随着不代表自由场爆炸的二次加载。爆炸波轮廓可以使用过渡段、锥形段和突然扩张段进行调整。我们观察到突然扩张配置的爆炸波轮廓存在振荡。由于突然扩张，激波管外部的位置受到喷流风效应的影响，出口处有一个狭窄区域除外。对于bTBI中推断的所需超压产量，在激波管内获得小于1毫秒的正相持续时间（这是啮齿动物研究中所追求的）具有挑战性。总体而言，这些结果强调，使用激波管复制自由场爆炸条件涉及需要仔细权衡的权衡，并且在实验室bTBI研究期间应评估它们对损伤结果造成的影响。
