A Numerical Study On Blast Wave/Noise By Muzzle Flows Discharging From Weapons

Unsteady complex muzzle flow field with high temperature, high pressure and high-speed, poses serious hazards on the gun operator, surrounding environment and the other equipment during weapons fire. Among them, the greatest hazards come from the muzzle blast wave and noise. In order to study the hazardous production mechanism and controlling methods, detailed investigations on the muzzle blast wave/noise are performed based on theory, experiment and numerical simulation in this paper.Firstly, the research background, the current research status and difficulties on muzzle blast wave/noise are described in this article. In the early classical computation theory of muzzle flow field, the calculation and prediction of muzzle noise is not involved. With the rapid advancement of computer technology and the development of numerical methods, it is possible to predict the complex muzzle flow field considering both the muzzle blast wave and noise.Secondly, the difference of muzzle blast wave and noise in physical characteristics is introduced in this paper. Also, the mechanism and effect of the damage on the human auditory and internal organs are quite distinct. It emphasizes the difference and correlation between the blast wave and noise in depth. Due to their differences, their research methods are quite different, particularly their numerical methods discussed in the paper. In order to investigate the applicability of numerical methods on muzzle blast wave, especially the numerical scheme, several validation cases have been done to simulate the muzzle blast field. Numerical results show that these methods are feasible. Based on this, the muzzle blast flow field of the recoilless gun and the mortar are numerically calculated from the launch safety point of view. According to the results, the developing process of muzzle flow field and the peak overpressure distribution are analyzed. These results provide actual reference in predicting the damage on the gun operator.Thirdly, because of its complex noise sources, to completely simulating the muzzle noise is very difficult. In this paper, the most typical highly under expanded jet noise is calculated as a starting study of muzzle noise. And the coupling calculation considering the muzzle blast wave and jet noise is carried out. The jet noise is calculated by two steps, the first one is the flow calculation by using LES, and the second is jet noise calculation by using the FW-H equation. The results show that the error of sound pressure level between the numerical and experimental results is no more than 6.3%. Finally, to solve the calculation error about the peak overpressure caused by the blast wave numerical solution (Its discontinuity was smoothed in some degree), further process on the numerical results should be given according to physical methods. It may be an effective way to reduce the numerical errors and improve accuracy. In this paper a good attempt is made by using the shock relationship to process the peak overpressure and the results show that the peak overpressure obtained by using physical correction is more accurate. In addition, under certain conditions, CFD can even be an effective alternative to experiments in some related experimental work. In this paper, the physics model of muzzle blast wave (establishment based on a large quantity of experiments) is validated by using the numerical method described in this article.