Numerical Simulation And Analysis Of The Muzzle Flow During The Small Caliber Multiple Revolving Barrels Gun Firing

The revolving barrel gun is the principal component of the Close-In Weapons System (CIWS). The defense against anti-ship cruise missile was derectly influenced by the gun’s shot accruracy. There will be unsteady high-temperature high-pressure muzzle complex shock waves during the revolving barrel gun firing and the shot ejection process has an important effect on the shot accuracy. Numerical methods were used to simulate and analysis the muzzle flow formation and development process and its affect on the projetile movement. The main parts of this research are concluded as follows:a) According to the actual physical process of the small caliber gun firing, the muzzle flow formation and development process is relational to the interior ballistic process. The interior ballistic lumped parameter model was solved using4th order Runge-Kutta scheme in the numerical simulation. The projectile movement law was got. The one-dimensional two-phase flow interior ballistic mathematical model was established and solved using MacCormack scheme in the numerical simulation. The change laws of interior ballistic parameters were analyzed. Base on the modeling results, the effect of different factors of the interior ballistic performance were discussed. The pressure distributions in the bore at shot exit ware obtained.b) Muzzle flow fields are simulated from the projectile engraving. Based on the mathematical assumptions, the muzzle flow simulation model coupled the interior ballistic process was established. Coupled with interior ballistics process, the2D axial symmetrical aerodynamic model was established to simulate muzzle flow field. The two models are coupled by the resistance of pressure in front of projectile. The agreement of the numerical results with experimental results shows that the model and method provided in the paper is reasonable and effective. The chang process of the muzzle flow was shown by simulation.c) During the gun firing, the muzzle flow field is high-temperature, high-pressure, high-velocity and includes normal shock, oblique shock, and intersection shock wave. According to the characteristics of muzzle flow, the BWIP (Blast Wave Identification Paramete) dynamic adaptive grid method with the numerical controller was established. The unsteady muzzle flow of the small caliber gun was simulated by solving two dimensional axisymmetric governing equations applying AUSM up scheme with the BWIP dynamic adaptive grid method. For the same shock capturing ability, the computer resource could be cut down. d) In order to enhance the shot accuracy of gun system, aerodynamic characteristics the rifled structure launching projectile was investigated while the projectile flying over the complex muzzle flow field. The projectile aerodynamic characteristics change laws were simulated by solving three dimensional N-S equations applying k-epsilon turbulence model with local refinement of unstructured grids. Numerical results of SOCBT (Secant Ogive Cylinder Boat Tail model) projectile are in good agreement with experimental results, so the used computational model and CFD method is effective and relative. Aerodynamic characteristic variation laws are simulated and analyzed due to different parameters, including attack angle, projectile rotating speed and incoming Mach number. The projectile body pressure asymmetry distribution and the characteristics of lift/drag were obtained and analyzed. Coupled with the interior ballistic process, the projectile velocity variations in different rotating speed were simulated and analyzed.e)The3D computational model was formulateated to illustrate the details of the flow field produced by the revolving barrel gun firing. The algorithm of a second order MUSCL approach with the AUSM+solver was used to simulate the high pressure muzzle flow field. The interior ballistic process was coupled with the simulation. The muzzle flow characteristics of the revolving barrel gun were illustrated by simulations. The muzzle flow field structure of a revolving barrel gun fire with no angle of attack was asymmetric while the projectile is flying through the flow.The maximum lateral velocity of the first and second projectile fired was about1.6m/s and3.8m/s.