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RESEARCH PAPERS: Interior Ballistics

Aerodynamic Analysis of Projectile in Gun System Firing Process

[+] Author and Article Information
Wei Yu, Xiaobing Zhang

School of Power Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

J. Appl. Mech 77(5), 051406 (Jun 10, 2010) (8 pages) doi:10.1115/1.4001559 History: Received January 06, 2010; Revised March 16, 2010; Posted April 08, 2010; Published June 10, 2010; Online June 10, 2010

During a gun firing, the flow around a projectile will be developing and changing. In particular, the flow around the projectile is disturbed significantly when the projectile overtakes the muzzle flow. Furthermore, the projectile body pressure will also change substantially. Therefore, the shot ejection process has an important effect on the shot accuracy. The maximum projectile velocity is one of the most important design goals of the interior ballistic process and also is the initial condition for the exterior ballistic process. Most researchers take the muzzle velocity as the maximum projectile velocity; actually, after the projectile exits the muzzle, the projectile velocity will increase further due to the influence of the muzzle flow. Most investigations of the muzzle flow focused on the blowout of the high-pressure jet flow after the projectile exited the muzzle. The interior ballistic process was ignored or simply assumed in most investigations. Also, the mutual influence between the moving projectile and the muzzle flow was often neglected. Actually, a precursor shock flow near the muzzle is formed before the projectile exits. This precursor muzzle flow has an important influence on the trajectory of the projectile, especially, for the prevalent trend of gun systems including large caliber cannon and multiple launch gun systems. For these reasons, the interior ballistic process was coupled with the simulation of the flow near the muzzle. A hybrid structured-unstructured gridding method was used to simulate the process from the projectile engraving to the gas ejection phase, accounting for the moving projectile. The simulation results show that the projectile muzzle velocity was 893.99 m/s but the maximum velocity was 899.28 m/s. The projectile velocity increased rapidly to up to 0.8 ms after muzzle exit; thereafter, the projectile velocity increased slowly before reaching its maximum value. The maximum Mach number of the effluent gas increased to 6.83 and the breech pressure decreased to 21.5 MPa at 1.8 ms after the projectile exited the muzzle. The formation and development of the muzzle flow field was highly complex and transient. The analysis of the projectile velocity was conducted during the interior ballistic after-effect period. The predicted muzzle velocity and maximum barrel pressure are in good agreement with those measured in gun firings. Results of the numerical simulation and analysis are helpful to understand and master the aerodynamic process of gun system launching and provide significant guidance for research into shot accuracy and muzzle brake design.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Muzzle flow schematic

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Figure 2

Initial mesh distribution in computational domain

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Figure 3

Boundary condition schematic

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Figure 4

Comparison between numerical results and the experimental photo

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Figure 5

Calculation results of the interior ballistic process

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Figure 6

Time development of the muzzle flow (pressure contours)

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Figure 7

Distribution of reference points

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Figure 8

Mach number-time curve of point 1 before muzzle exit

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Figure 9

Pressure-time curves of reference point

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Figure 10

Simulation results profile along axis of symmetry

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Figure 11

Velocity contours and projectile body pressure distribution at the various times

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Figure 12

Mach number distributions behind the projectile

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Figure 13

Pressure distributions behind the projectile

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Figure 14

Velocity vector before the projectile exited

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Figure 15

Velocity-time curve of the projectile after the projectile exited

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