A methodology to simulate interior and intermediate ballistics with dynamic mesh technique and lumped parameter code

The aim of this paper is to simulate and study the early moments of the reactive ballistics of a large caliber projectile fired from a gun, combining 0D and 2D axisymmetric Computational Fluid Dynamics (CFD) approaches. First, the methodology is introduced with the development of an interior ballistics (IB) lumped parameter code (LPC), integrating an original image processing method for calculating the specific regression of propellant grains that compose the gun propellant. The ONERA CFD code CEDRE, equipped with a Dynamic Mesh Technique (DMT), is then used in conjunction with the developed LPC to build a dedicated methodology to calculate IB. First results obtained on the AGARD gun and 40 mm gun test cases are in a good agreement with the existing literature. CEDRE is also used to calculate intermediate ballistics (first milliseconds of free flight of the projectile) with a multispecies and reactive approach either starting from the gun muzzle plane or directly following IB. In the latter case, an inverse problem involving a Latin hypercube sampling method is used to find a gun propellant configuration that allows the projectile to reach a given exit velocity and base pressure when IB ends. The methodology developed in this work makes it possible to study the flame front of the intermediate flash and depressurization that occurs in a base bleed (BB) channel at the gun muzzle. Average pressure variations in the BB channel during depressurization are in good agreement with literature.