International audienceTo understand the blast effects of confined explosions, it is necessary to study the characteristic parameters of the blast wave in terms of overpressure, impulse and arrival time. In a previous study, experiments were performed using two different scales of a pyrotechnic workshop. The main purpose of these experiments was to compare the TNT equivalent for solid and gaseous explosives in terms of mass to define a TNT equivalent in a reflection field and to validate the similitude between real and small scales. To study the interactions and propagations of the reflected shock waves, the present study was conducted by progressively building a confined volume around the charge. In this way, the influence of each wall and the origins of the reflected shock waves can be determined. The purpose of this paper is to report the blast wave interactions that resulted from the detonation of a stoichiometric propane-oxygen mixture in a confined room
The purpose of this paper is to report the blast loading characteristics resulting from the detonation of a stoichiometric propane-oxygen mixture, and to validate the approach which relies on simulating TNT explosions at large scale by small scale experiments of gaseous explosions. Several dimensionless correlations are obtained from experimental data. These relationships allow determination of the parameters of a blast wave interacting with a structure as a function of the positions of the explosive charge and the structure. Simulations carried out with the Autodyn code show good correlation with experimental results. The Hopkinson law is suggested to predict the blast wave's parameters at large scale on the basis of small scale experiments and simulations.
Interaction between large blast and targets can rarely only be directly studied, due to cost and practicality considerations. Blast tests using reduced-scale high explosive charges represent an attractive alternative. The first necessary step consists in studying blast propagation in free-field at the considered scales. The second step focuses on the determination of the blast load around various types of reference obstacles, in order to provide a critical input for numerical simulation. This approach also aims to build simplified models allowing faster risk assessment for government agencies. Since 2017, the French Institute for Nuclear Safety (IRSN) and the French-German Research Institute of Saint-Louis (ISL) have been studying blast propagation in free-field and in front of a hemi-cylinder at two different reduced scales using Hexomax ® charges. IRSN developed a significant experience on hemispherical blast effect assessment using 42 g reference Hexomax ® charges detonated in contact with a planar surface supporting a hemi-cylindrical obstacle, both equipped with pressure sensors. Based on this experience, ISL developed its own outdoor blast-pad: 333 g Hexomax ® charges are detonated in a factor two up-scaled version of IRSN test configuration. Similar sensors are flush-mounted on the pad and the surface of an up-scaled version of the IRSN obstacle. In addition, the fine structure of the shock transmitted into the air and propagating along the obstacle surface is studied using high-speed imaging. Two respective series of charges were detonated at distances between 0.6 and 3.5 m/kg 1/3 from the hemi-cylinder, in order to assess its influence on the wave reflection structure and the resulting blast load. High-speed images enabled the triple and contact points tracking on the obstacle. Finally, this project illustrates an innovative methodology not only to assess the blast load on a convex structure, but also the potential downstream protective effects of such a structure used as a barrier.
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