A Note on the Blast Signature of a Cannon
ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
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In a recent experiment with a small caliber cannon, it was found that the early portion of the blast signature was predicted quite well by an inviscid code, but at later times, a secondary shock appeared upstream that was not present in the experiment. The wave is generated as the plume shear layer curls up to form the vortex just downstream of the shock bottle. The second-order solver captures the shear layer more as a slip surface, and the gas stream passing through it retains too much kinetic energy. The shock brings the stream into mechanical equilibrium with the gas ahead of it by converting the excess energy into internal energy. Using a more dissipative solver in the shear layer reduces the kinetic energy of the stream and the shock strength upstream. It is concluded that a practical limit exists for an inviscid calculation of muzzle blast beyond which more realistic dissipative mechanisms must be introduced. Muzzle Blast, Blast Simulation, Cannon Blast Flow Field.