Estimation of the increase in projectile velocity in the intermediate ballistics period

Central European Journal of Energetic Materials, 2015, 12(1), 63-76 p.
ISSN 2353-1843The idea of the application of internal ballistics models together with external ballistics models in fire control systems encounters a problem in relating the calculated muzzle velocity value to the initial velocity value used in external ballistics calculations. The difference between these two values is caused by the action on the projectile of the propellant gases exiting from the muzzle. In this paper an attempt has been made to estimate the increase in projectile velocity outside the muzzle by the use of CFD modelling. The commercial ANSYS FLUENT code has been used together with our own 1D model for the internal ballistics period. Calculations have been performed for various launching systems, from small arms to a 155 mm calibre gun. Conclusions have been drawn concerning the magnitude of the increase in projectile velocity outside the muzzle. The main conclusion is that the velocity increase is generally less than 1% and in most cases can be neglected.