Explosive blasts or explosions are physical phenomena that result in a sudden release of energy. This process causes a near instantaneous compression of the surrounding medium (e.g., air or water) and an increase in pressure ("overpressure") above atmospheric pressure, resulting in an overpressure wave (or blast wave)(Cernak, 2015). This overpressure wave propagates outward from the explosion in a radial fashion at supersonic speed, creating a wake of negative pressure ("underpressure") that follows behind. After the negative pressure wave passes, relative pressures return to baseline.
A blast wave is an area of pressure expanding supersonically outward from an explosive core. It has a leading shock front of compressed gases. The blast wave is followed by a blast wind of negative pressure, which sucks items back in towards the center. The extent of damage caused by the blast wave mainly depends on five factors:
Blast waves from explosions that occur near or within hard solid surfaces can be amplified two to nine times because of shock wave reflection, causing an increase in their destructive potential (Stewart, 2004). For example, people located between a blast and a building will often suffer more extensive injuries than when the blast occurs in an open space. Because blast waves reflect, people exposed to an explosion rarely experience an idealized blast waveform as depicted above. Even in open field conditions, the primary blast wave reflects from the ground, generating reflective waves that interact with the primary wave and change its characteristics. In more closed environments, such as a building, an urban setting, or the inside of a vehicle, the blast wave interacts with the surrounding structures creating multiple complex waves (Ben-Dor et al., 2001; Mainiero and Sapko, 1996).
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