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Numerical investigation on free air blast loads generated from center-initiated cylindrical charges with varied aspect ratio in arbitrary orientation

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Defence Technology（防务技术） 2022年第9期18卷 1662-1678页

作者： Chu Gao Xiang-zhen Kong Qin Fang Jian Hong Yin Wang State Key Laboratory of Disaster Prevention&Mitigation of Explosion&Impact Army Engineering University of PLAJiangsuNanjing210007China Inner Mongolia University of Finance and Economics Inner MongoliaHohhot010070China Engineering Research Center for Safety and Protection of Explosion&Impact of Ministry of Education Southeast UniversityJiangsuNanjing211189China

In current guidelines, the free air blast loads(overpressure and impulse) are determined by spherical charges, although most of ordnance devices are more nearly cylindrical than spherical in geometry. This may result in a great underestimation of blast loads in the near field and lead to an unsafe ***, there is still a lack of systematic quantitative analysis of the blast loads generated from cylindrical charges. In this study, a numerical model is developed by using the hydrocode AUTODYN to investigate the influences of aspect ratio and orientation on the free air blast loads generated from center-initiated cylindrical charges. This is done by examining the pressure contours, the peak overpressures and impulses for various aspect ratios ranged from 1 to 8 and arbitrary orientation monitored along every azimuth angle with an interval of 5°. To characterize the distribution patterns of blast loads,three regions, i.e., the axial region, the vertex region and the radial region are identified, and the propagation of blast waves in each region is analyzed in detail. The complexity of blast loads of cylindrical charges is found to result from the bridge wave and its interaction with primary waves. Several empirical formulas are presented based on curve-fitting the numerical data, including the orientation where the maximum peak overpressure emerges, the critical scaled distance beyond which the charge shape effect could be neglected and blast loads with varied aspect ratio in arbitrary orientation, all of which are useful for blast-resistant design.

关键词： Cylindrical charge blast loads Aspect ratio Azimuth angle Bridge wave

blast waveform tailoring using controlled venting in blast simulators and shock tubes

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Defence Technology（防务技术） 2024年第7期37卷 14-26页

作者： Edward Chern Jinn Gan Alex Remennikov David Ritzel Faculty of Engineering and Information Sciences University of WollongongWollongongNSW2522Australia Dyn-FX Consulting Ltd 19 Laird Ave NorthAmherstburgONN9V 2T5Canada

A critical challenge of any blast simulation facility is in producing the widest possible pressure-impulse range for matching against equivalent high-explosive *** tubes and blast simulators are often constrained with the lack of effective ways to control blast wave profiles and as a result have a limited performance *** wave shaping techniques employed in some facilities are reviewed but often necessitate extensive geometric modifications,inadvertently cause flow anomalies,and/or are only applicable under very specific *** paper investigates controlled venting as an expedient way for waveforms to be tuned without requiring extensive modifications to the driver or existing geometry and could be widely applied by existing and future blast simulation and shock tube *** use of controlled venting is demonstrated experimentally using the Advanced blast Simulator(shock tube)at the Australian National Facility of Physical blast Simulation and via numerical flow simulations with Computational Fluid *** venting is determined as an effective method for mitigating the impact of re-reflected waves within the blast *** control method also allows for the adjustment of parameters such as tuning the peak overpressure,the positive phase duration,and modifying the magnitude of the negative phase and the secondary shock of the blast *** paper is concluded with an illustration of the potential expanded performance range of the Australian blast simulation facility when controlled venting for blast waveform tailoring as presented in this paper is applied.

关键词： Advanced blast simulator Shock wave propagation Far-field explosion blast loads blast waves Computational fluid dynamics

A simplified approach to modelling blasts in computational fluid dynamics (CFD)

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Defence Technology（防务技术） 2023年第5期23卷 19-34页

作者： D.Mohotti K.Wijesooriya S.Weckert School of Engineering and Information Technology The University of New South WalesCanberraACT2600Australia Sensors and Effectors Division Defence Science and Technology GroupEdinburghSA5111Australia

This paper presents a time-efficient numerical approach to modelling high explosive(HE)blastwave propagation using Computational Fluid Dynamics(CFD).One of the main issues of using conventional CFD modelling in high explosive simulations is the ability to accurately define the initial blastwave properties that arise from the ignition and consequent *** codes often employ Jones-Wilkins-Lee(JWL)or similar equation of state(EOS)to simulate ***,most available CFD codes are limited in terms of EOS *** are restrictive to the Ideal Gas Law(IGL)for compressible flows,which is generally unsuitable for blast *** this end,this paper presents a numerical approach to simulate blastwave propagation for any generic CFD code using the IGL EOS.A new method known as the Input Cavity Method(ICM)is defined where input conditions of the high explosives are given in the form of pressure,velocity and temperature time-history *** time history curves are input at a certain distance from the centre of the *** is shown that the ICM numerical method can accurately predict over-pressure and impulse time history at measured locations for the incident,reflective and complex multiple reflection scenarios with high numerical accuracy compared to experimental *** ICM is compared to the Pressure Bubble Method(PBM),a common approach to replicating initial conditions for a high explosive in Finite Volume *** is shown that the ICM outperforms the PBM on multiple fronts,such as peak values and overall overpressure curve ***,the paper also presents the importance of choosing an appropriate solver between the Pressure Based Solver(PBS)and Density-Based Solver(DBS)and provides the advantages and disadvantages of either *** general,it is shown that the PBS can resolve and capture the interactions of blastwaves to a higher degree of resolution than the *** is achieved at a much higher computational cos

关键词： blast loads Computational fluid dynamics Explosions Numerical simulations