Computer Simulation of a 155-mm Projectile in a Scat Gun Assembly

摘要

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 acceleration/deceleration of the piston inside the assembly in a long tube attached to the gun barrel. The projectile had an entrance velocity of 516 m/s 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 piston's 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.