Evaluation of the Computer Codes BLAST, DORF, HELP and HEMP for Suitability of Underexpanded Jet Flow Calculation
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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The computer codes BLAST, DORF, HELP and HEMP have been used to simulate the flow field at the muzzle of a M-16 rifle, without any deflectors, compensators, or flash hiders. The flow was modeled as an underexpanded jet, of a compressible, inviscid and non-reactive gas. The calculations, restricted to the initial stages of formation of the jet were done on a cylindrically symmetric geometry without the presence of a flow obstruction in the form of a projectile. Results are presented as pressure contours as well as pressure and velocity profiles at different angles from the centerline of the muzzle of the barrel, and plots of pressure versus distance from the muzzle. The calculations are compared with available photographic records of the process.