Computer Simulation of a 155-mm Projectile in a Scat Gun Assembly
ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER PICATINNY ARSENAL NJ
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This report presents the results of a computer simulation of a 45.36 kg 155-mm projectile as it moves through a scat gun assembly using a FORTRAN program. The experimental data was taken from a test performed by the Analysis Engineering and Technical Division at the U.S. Army Armament Research, Development and Engineering Center, Picatinny Arsenal, New Jersey on 7 April 2007 test CBR5. The data was filtered using an Abaqus Butterworth Filter with a cutoff frequency of 500 Hz because the data plot exhibited noisy displays due to the electronic circuitry. The simulation entails aerodynamic deceleration of the projectile and the accelerationdeceleration of the piston inside the assembly in a long tube attached to the gun barrel. The projectile had an entrance velocity of 516 ms and the shock wave preceding it ruptures the diaphragm. The projectile decelerates as high pressure builds between it and the free piston due to shock-wave propagation. The piston disengages and travels forward scooping water. The waterlog that forms in front of the piston effectively increases the pistons mass and also induces a braking force because of the water friction with the tube wall. The simulation predicts the piston will be decelerated with the piston coming to a rest about 22 m from the back end of the assembly. The computer simulation is based on the closed form formulas, incorporating unsteady one-dimensional fluid dynamics. This report details effects of shockwave induced pressure on the projectile and piston and how accurate the simulations are compared to the actual data lot.
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