Numerical study of a foam-shock trap based blast mitigation strategy

TLDR: In this article, a combination of foam and a shock trap was used to mitigate the effects of the blast wave on the target/protected structure, which significantly reduced the peak load and impulse experienced by the target.

Abstract: Blast mitigation using various types of foams is of interest to practitioners for the safe design of structures. Experimental and numerical studies have demonstrated the beneficial effects of different foam materials when used as protective soft coatings. However, under certain blast loading conditions and foam dimensions, the load experienced by the target/protected structure was found to be much higher in the presence of foam than in its absence. In this study, a mechanism based on geometric means known as shock trap is used along with foam as a preventive measure against shock amplification. A shock trap is a special arrangement of rigid obstacles with an air gap, designed to offer a tortuous flow path. To analyze the proposed foam-shock trap combination, a popular Lagrangian based Smoothed Particle Hydrodynamics (SPH) is employed. A novel solid wall boundary modeling technique called skew gradient wall boundary treatment is also built into the SPH solver. The material discontinuity is handled by a multimass correction strategy. The blast wave mitigation characteristics of the proposed approach are evaluated using two different foam materials, namely, wet aqueous foam and polystyrene foam. From detailed simulations, it was observed that undesirable shock enhancement effect of foams was found to be completely suppressed by combining it with the shock trap mechanism. The proposed foam shock trap combination significantly reduces the peak load and impulse experienced by the target structure.