Experimental and Numerical Investigation of Shock Wave Attenuation by Dynamic Barriers

Abstract

An explosion at the entrance of an underground bunker and a suicide bomber inside an airplane are examples of scenarios in which blast waves propagate in tunnels and corridortype structures. The need to attenuate the shock/blast wave propagating downstream a corridor and mitigate the developed loads inside the structure is essential. The interaction of a shock/blast wave with an obstacle inside a tunnel can dramatically reduce its strength. Earlier researches revealed that the dominant parameter in attenuating a shock wave by rigid barriers is the barrier opening ratio (i.e., the cross section that is open to the flow divided by the total cross section of the tunnel). Decreasing the opening ratio from 0.6 to 0.2 increased the attenuation by about 40%. Based on strong dependence of the attenuation on the opening ratio, a barrier designed to adjust its opening ratio to the loads exerted upon it is essential. In our previous study, we found that the effect of the rigid barrier geometry becomes more significant when the barrier inclination angle is larger, i.e., the barriers inclined toward the oncoming shock wave were found to be more effective in reducing the transmitted shock wave intensity than those inclined in the opposite direction. The pressure difference between both sides of the barrier exerts massive loads on the barrier. In the present ongoing research, based on a numerical approach using a commercial solver (msc.dytran), we focus on the geometry of a dynamic barrier, which changes its orientation as a response to the loads exerted on it. As a result, the barrier opening ratio, which as mentioned earlier strongly affects the shock wave attenuation, changes too. In this study, the feasibility of a dynamic barrier and the complex flow regime around it are investigated. The rapid pressure drop downstream of the barrier depends both on the shock wave strength and the barrier material and geometrical properties. Barriers with various geometries and properties are used to investigate the concept of a deflecting/rotating barrier as a response to the shock wave loads exerted upon it. For the first time, a new and exciting proven concept of a dynamic barrier, which reacts to the loads exerted upon it from a passing shock wave, and dramatically reduces the shockinduced pressure jump downstream of the barrier, is demonstrated.