The Effect of Ambient Pressure on Blast Reflected Impulse and Over Pressure
Dr. Roger Veldman
The goal of this project was to create a numerical model to predict the reflected blast pressure and impulse from a spherical charge of the high explosive C4 under varying atmospheric pressure conditions. For this study, a two dimensional Arbitrary Lagrangian Eulerian analysis was conducted using the commercial finite element analysis program LS-Dyna. Numerical predictions were carried out at a standoff distance of 24 inches and compared to measured pressure and impulse data. Based on the good correlation observed between the numerical predictions and experimental results at a 24 inch standoff, the computer model was then used for standoff distances in the range of 5 to 24 inches. The numerical predictions indicate that the normally reflected peak pressures were not significantly affected by varying ambient air pressure. In contrast, the reflected impulses values were predicted to increase with increasing ambient air pressure. The effect of ambient pressure on impulse was shown to decrease as the standoff distance decreases. In summary, at small standoff distances, the ambient pressure surrounding the high explosive charge has little effect on reflected blast impulse. For larger standoff distances, however, the reflected blast impulse increases with increasing ambient air pressure.
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