Abstract The sensitizing effect of cavities in the form of microbubbles on the shock initiation of a homogeneous liquid explosive is studied computationally. While the presence of voids in an explosive has long been known to induce so-called hot spots that greatly accelerate the global reaction rate, the ability to computationally resolve the details of the interaction of the shock front with heterogeneities existing on the scale of the detonation reaction zone has only recently become feasible. In this study, the influence of the spatial distribution of air-filled cavities has been examined, enabled by the use of graphic processing unit (GPU) accelerated computations that can resolve shock initiation and detonation propagation through an explosive while fully resolving features at the mesoscale. Different spatial distributions of cavities are examined in two-dimensional simulations, including regular arrays of cavities, slightly perturbed arrays, random arrays (with varying minimum spacing being imposed on the cavities), and randomly distributed clusters of cavities. Statistical ensembles of simulations are performed for the cases with randomly positioned cavities. The presence of the cavities is able to reduce the time required to initiate detonationfor a given input shock strength—by greater than 50%, in agreement with previous experimental results. Randomly distributing the cavities results in a 15–20% decrease in detonation initiation time in comparison to a regular array of cavities. Clustering the cavities—as would occur in the case of agglomeration—results in an additional 10% decrease in detonation initiation time in comparison to random arrays. The effect of clustering is shown not to be a result of the clusters forming an effectively larger cavity, but rather due to interactions between clusters upon shock loading occurring on the microscale. The implications of these results for modelling and experiments of microbubble-sensitized explosives is discussed.

中文翻译：

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中尺度非均质性空间分布对液态硝基甲烷冲击-爆轰转变的影响

摘要 计算研究了微泡形式的空腔对均质液体炸药起爆冲击的敏化作用。虽然长期以来人们都知道炸药中存在空隙会引起所谓的热点，从而大大加快全球反应速率，但能够通过计算解决激波前沿与爆炸规模上存在的不均匀性相互作用的细节反应区直到最近才变得可行。在这项研究中，通过使用图形处理单元 (GPU) 加速计算，检查了充气空腔的空间分布的影响，该计算可以解决冲击引发和爆炸通过炸药的传播，同时完全解决中尺度特征. 在二维模拟中检查了空腔的不同空间分布，包括空腔的规则阵列、微扰阵列、随机阵列（对空腔施加了不同的最小间距）和随机分布的空腔簇。对具有随机定位腔的情况执行模拟的统计集成。对于给定的输入冲击强度，空腔的存在能够将起爆所需的时间减少 50% 以上，这与之前的实验结果一致。与规则的空腔阵列相比，随机分布空腔可使起爆时间减少 15-20%。与随机阵列相比，将空腔聚类（如在团聚的情况下会发生）导致起爆时间额外减少 10%。聚类的影响不是由于簇形成了一个有效的更大的空腔，而是由于在微观尺度上发生冲击载荷时簇之间的相互作用。讨论了这些结果对微泡敏化炸药建模和实验的影响。