Towards the accurate simulation of shock-waves around weapon systems

The objective of this study is to examine the evolution of the pressure field around a weapon being fired in order to improve the environment for the operating personnel. When a weapon is fired the propellant burns resulting in a rapid pressure and temperature increase by which the warhead is ejected. Depending on weapon system the shock-waves, are of different strength: for a rifle the shooter needs to wear ear plugs in order to avoid hearing impairment, whereas, for a howitzer, the personnel also need to wear ear cups. Alternatively, mufflers can be used with marginal effect on the efficiency of the weapon. The most common method of studying pressure around weapons being fired is by means of experiments, but recently also computations, based on first principles, are being carried out. Within the framework of this study, an existing code has been further developed to handle the specific issues pertinent to shock-waves around weapons. Within the framework of this study, this code is validated against a traditional Riemann problem, and later applied to the Swedish PSG 90 rifle. The results are examined with respect to the spatio-temporal evolution of the pressure field and the character of the pressure signal at the shooters position. For simplicity, we have here neglected the effects of the bullet and the volumetric expansion due to exothermicity. We also discuss the possibilities of improving the present computational methodology with the intent of improving it´s accuracy and expanding the range of applicability to other weapon systems and to include other effects, such as the effects of exothermicity and shock waves produced by the bullet.