远距离近地面爆炸空气冲击波计算的网格尺寸优化与验证

Optimization and verification of mesh size for air shock wave from large distance and near ground explosion

建筑结构上爆炸荷载的确定是进行结构动态响应和损伤破坏分析以及结构抗爆设计和加固的前提。考虑到空气爆炸冲击波远距离传播数值模拟计算效率和精度以及软硬件能力的平衡问题,通过确定和优化网格尺寸,从而为大型复杂街区爆炸冲击波荷载的数值模拟网格尺寸选取提供合理建议。针对汽车炸弹和弹药库等典型近地面爆炸场景,首先,使用AUTODYN软件分别开展比例距离为0.2~5.0 m/kg^(1/3)和0.2~39.0 m/kg^(1/3)的空中爆炸自由场和地面爆炸入射场超压和冲量的单一尺寸网格敏感性分析,并考虑软硬件对单元网格数量的限制,给出依赖比例距离的渐变网格尺寸建议。其次,基于映射算法和建议的渐变尺寸网格对地面爆炸入射场超压和冲量进行数值模拟,提出了比例距离大于10.0 m/kg^(1/3)的峰值超压误差修正方法,并得到UFC 3-340-02规范的验证。最后,基于足尺房屋爆炸荷载分布试验共71个测点的超压和冲量时程数据,对提出的优化网格尺寸的计算精度和效率进行了验证。

The determination of the blast loading on building structures is a prerequisite for the analyses of dynamic response and damage mode,as well as the blast-resistant design and the structural reinforcement.In determining the blast loadings on building structures with the upgraded computing hardware and software,the low-cost and high-safety numerical simulation methods have increasingly attracted the attention of researchers.In order to improve the computing efficiency and accuracy,and to balance the capacities of both the hardware and the software,by adopting the simplified calculation method,i.e.,using symmetry(1D-2D-3D extension)and remapping method,the optimized sets of mesh sizes for the numerical simulation of blast wave propagating for a long distance in large complex block are proposed.Firstly,aiming at the typical near-ground explosion scenarios,e.g.,car bombs and ammunition depots,the sensitivity analyses of single-size mesh based on incident wave of air and ground explosions at the scaled distances of 0.2−5.0 m/kg^(1/3) and 0.2−39.0 m/kg^(1/3) are carried out,respectively.Secondly,considering the limitations of the software and hardware,a set of gradient mesh sizes against the scaled distances is recommended.Furthermore,based on the remapping technique and the suggested gradient mesh sizes,the incident overpressure and impulse of ground explosion are numerically calculated,and an improved method for correcting the peak overpressure with the scaled distances larger than 10.0 m/kg1/3 is proposed,which is then verified by UFC 3-340-02.Finally,the computing accuracy and efficiency of the proposed optimized mesh sizes are verified by comparing the simulated and experimental overpressures and impulses(71 gauges)in the field explosion test on a full-scaled building.Besides,the applicability of the proposed gradient mesh size in simple reflection field is verified,which provides a reference for the subsequent proportional amplification application of gradient mesh size and the simulation application of blast loadings in more complex reflection environment.