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Abstract
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Explosion hazard modeling is a challenging problem since it involves several physical, often complex, interacting aspects. In combustion explosions, the available quantity of energy changes rapidly and is constantly redistributed among heat, the kinetic and chemical energy forms. The problem becomes even more complex when the subsequent blast wave propagation is assumed to interact with the nearby structures. Structural damage is mainly due to the incident blast wave, but the successive reflections also have a significant effect in congested areas. In confined or semi-confined areas, damage is more likely to happen far from the detonation source since high velocity fragments are assumed to be projected outward. Obstructions and blast waves interact closely since the blast wave impulses affect the structures and may cause failures, while the structures in turn modify the blast wave's propagation patterns.
For the above reasons, it is important to have a profound understanding of exactly what kind and what levels of blast loading take place when a shock wave propagates from a blast in a terrain obstructed by building. Some approximate and empirical formulae have already been derived to predict the maximum pressure and the effect of the impulse on structures for both open and congested terrains. However, when they are not impossible due to safety and environmental considerations, explosion tests are still expensive and awkward to set up. With the development of computing power and the increasing sophistication of computational methods, it has become possible to use numerical techniques to predict blast loading and blast effects on structures.
The guidelines for protecting against and mitigating explosion hazards require knowledge and either the experimental or theoretical evaluation of blast wave parameters. To this end, this article proposes a numerical method for simulating blast wave propagation in complex geometries. This method permits an on-the-ground TNT-like explosion and the subsequent blast wave to be simulated, with the possibility of modifying the ground topology by adding a number of obstacles. The numerical model is explored from both a qualitative and quantitative point of view by comparing it to experimental data, with a correct determination of the wave amplitude and phase signature at different key-positions. The pressure and Mach number distributions deduced from simulations in complex congested areas highlight various fluid-solid interactions, such as regular reflections and diffractions. The iso-damage diagrams of different obstacle layouts are also presented and discussed. |