Blast overpressure relief using air vacated buffer medium

Abstract

Blast waves generated by intense explosions cause damage to structures and human injury. In this thesis, a strategy is investigated for relief of blast overpressure resulting from explosions in air. The strategy is based on incorporating a layer of low pressure-low density air in between the blast wave and the target structure. Simulations of blast waves interacting with this air-vacated layer prior to arrival at a fixed wall are conducted using a Computational Fluid Dynamics (CFD) framework. Pressure histories on the wall are recorded from the simulations and used to investigate the potential benefits of vacated air layers in mitigating blast metrics such as peak reflected pressure from the wall and maximum transmitted impulse to the wall. It is observed that these metrics can be reduced by a significant amount by introducing the air-vacated buffer especially for incident overpressures of the order of a few atmospheres. This range of overpressures could be fatal to the human body which makes the concept very relevant for mitigation of human blast injuries. We establish a functional dependence of the mitigation metrics on the blast intensity, the buffer pressure and the buffer length. In addition, Riemann solutions are utilized to analyze the wave structure obtained from the blast-buffer interactions for the interaction of a uniform wave an air-depleted buffer. Exact analytical expressions are obtained for the mitigation obtained in the incident wave momentum in terms of the incident shock pressure and the characteristics of the depleted buffer. The results obtained are verified through numerical simulations.

(cont.) It is found that the numerical results are in excellent agreement with the theory. The work presented could help in the design of effective blast protective materials and systems, for example in the construction of air-vacated sandwich panels. Keywords: Blast Mitigation, Air-depleted Buffer, Low Pressure, Blast Waves, Sandwich Plates, Numerical Simulations