Journal of Modern Mathematics Frontier Vol. 1 Iss. 4, December 2012 7 Computational Investigation of Blast-wave- mitigation via the Use of Air-vacated Buffers M. Grujicic, J. S. Snipes, N. Chandrasekharan Department of Mechanical Engineering Clemson University Clemson, SC, 29634, USA gmica@clemson.edu Abstract Several experimental investigations reported in the open literature have indicated that the application of reduced pressures of air (within a closed vessel) carrying detonation- induced blast waves can substantially reduce the intensity of blast loading experienced by the target test-structure (placed inside the vessel). To examine the feasibility and potential of this air-vacation concept in protecting target structure/personnel under more realistic combat-theatre conditions, the use of air-vacated buffers placed in front of the target structure is investigated in the present work. Towards that end, advanced fluid-structure interaction, non- linear dynamics, finite-element analyses are carried out on the phenomena and processes accompanying blast wave generation, propagation and interaction with air/buffer and buffer/target-structure interfaces. To verify and validate the employed computational methods and tools, it was first shown that they can quite accurately reproduce analytical solutions for a couple of well-defined blast wave propagation and interaction problems. To quantify the blast/mitigation efficiency of the air-vacated buffer concept, two metrics are utilized: (a) the peak pressure experienced by the target structure; and (b) the total momentum/impulse transferred by the incident blast wave to the target structure. The results obtained clearly revealed that significant blast-mitigation effects can be achieved through the use of the air-vacated buffer concept and that the extent of the blast-mitigation effect is a sensitive function of the buffer geometrical and vacated-air material-state parameters (e.g., pressure, mass density, etc.). It has also been shown that, in order to fully exploit the air-vacated buffer concept, timely deployment of the buffer is very critical. Keywords Blast-wave-mitigation; Air-vacation; Computational Analysis Introduction The main objective of the present work is to utilize advanced fluid-structure interaction computational methods and tools in order to assess the blast- mitigation potential of air-vacated buffers placed between the incident blast wave(s) and the target structure/personnel. Hence, the key aspects of the present work are: (a) blast-wave-loading; (b) shock/blast-wave-mitigation strategies/concepts; and (c) use of air-vacated buffers in blast-wave-mitigation applications. These aspects will be briefly overviewed in the remainder of this section. It should be noted that the term “blast wave” is used here to denote a high- intensity detonation-induced wave within the air surrounding the explosive charge, while the term “shock” is used to denote the high intensity wave within the target structure generated as a result of the interaction of the incident blast wave with the target structure. Blast-wave-loading: Blast waves are high intensity waves which propagate through a fluid medium (e.g. air) and after collision with target structures exert time- dependent loading on to the structures, transferring to them substantial momentum and kinetic energy. Blast waves are generally produced as a result of intentional or accidental explosions. In the combat theatre, explosions are normally intentional and result from the detonation of various explosives. In the civilian/industrial environment, on the other hand, explosions are often the result of accidents or negligence. Regardless of the circumstances under which explosions occur, there is a general need to develop blast-resistant structures which could protect infrastructure and personnel. Development of such structures is generally costly, time consuming and involves destructive (one-shot) testing. Consequently, in order to shorten the time and reduce the cost of such development, full-scale testing is increasingly being complemented (and often replaced) with subscale testing and computational engineering analyses (CEA) [1-5]. In the present work, advanced CEA methods and tools are used in the analysis of an air-vacated buffer based blast-wave-mitigation strategy.