Blast Wave Mitigation by a Particulate Foam Barrier

Abstract

Blast waves mitigate in foam due to various mechanisms, whose contribution to the final result is not fully understood yet. Actually, blast waves can destroy the foam barrier that is usually prone to decay and thus subsides with time. Fortunately, different time scales allow separating between these processes. The foam shattering, for example, could be completed within several milliseconds, while the foam decay lasts minutes and even hours. Recently, an increasing interest in this area has emerged, because particle-laden foams are much more stable and thus, could be applied for blast wave protection. To explore the full advantage of these new foams, the relationship between the micro-properties of the foam structure and the blast wave mitigation has to be clarified. In order to specify this relationship, little has been done. Information available in the literature on this subject clearly shows that during the test, the foam structure could be changed in a wide range, which is not usually controlled. This complicates the analysis of the occurring processes and ensures that the new factor involved in the studied problem has to be tested one by one, after the result of the previous step is well understood. To follow this strategy, this study continues our previous investigation (Britan et al in Colloid Surf A Physicochem Eng Aspects 309:137–150, 2007; Colloid Surf A Physicochem Eng Aspects 344:15–23, 2009; 2011), while mainly focusing on a single new factor, namely blast-shaped profile. To separate out the effect of the foam decay, which was discussed elsewhere (Britan et al in 2011), a special effort has been spent to ensure that the tested foam is homogeneous over its height. To exclude the bubble shattering, preference was given to weak impact conditions (Mach number of the shock generated inside the shock tube was about MS = 1.05). Under these circumstances, the blast wave mitigation inside the tested foam barrier solely depended on the concentration of the solid additives.