Numerical Simulation And Analysis Of Aircraft Gun Muzzle Flow Fiel

When an airborne cannon is launched in the air,the shock wave,noise wave,muzzle flame and other phenomena generated by the muzzle flow field will cause a series of negative effects.Using the numerical method in this paper,the formation mechanism of the aircraft gun muzzle flow field under the coupling of multiple factors,the noise field distribution characteristics of the high-altitude air gun muzzle and the muzzle installation dual-hole device to suppress the muzzle flow field hazards have been deeply studied..The research content is of great significance for improving the launch performance of weapons and ensuring the safety of pilots and airborne and ensuring the safety of pilots and airborne equipment.The main research contents of the full text are as follows:(1)Successfully used the theoretical knowledge of computational fluid dynamics to construct a numerical model of the aircraft gun muzzle flow field.In terms of numerical verification: the numerical model of the 7.62 mm caliber rifle was constructed,and the feasibility of the numerical calculation method in this paper was verified from the angles of high altitude and high speed.The calculation result is compared with the range test,and it is found to be consistent with the actual situation.(2)The Realizable k-epsilon model is used to calculate the muzzle flow field with or without a pod,and the differences between the two are compared.The calculation results show that the propagation distance of the upstream shock wave front of the muzzle is positively correlated with the incoming flow under the condition of no pod,and the downstream is the opposite;affected by the incoming flow,the jet core area and structure composed of the Mach disk and the bottle shock wave The size has changed,and the growth of the bottle shock wave is suppressed.The axial parameters of the muzzle and the shock wave over pressure are also affected by the incoming flow.Under the condition of the pod,the steady-state oblique shock wave of the pod and the gunpowder gas shock wave are coupled and developed.The shock wave is obstructed by the wall,and the over pressure value at this position changes.Under steady-state flight conditions,the incoming flow Mach number is constant,and the greater the distance between the gun muzzle and the gondola,the smaller the shock wave resistance on the gondola wall and the obvious drag reduction effect.(3)Large eddy simulation(LES)is used to predict the noise field of the aircraft gun muzzle,and the change characteristics of the air gun noise field of the pod under various factors are analyzed.Studies have shown that: the incoming flow has a certain speed,and the sound pressure levels of different radii and angular positions have obvious directivity;the existence of incoming flow will increase the turbulent pulsation action,and the sound pressure level will become higher;when the flight altitude reaches a certain height,the turbulent pulsation action The attenuation is obvious,and the sound pressure level is reduced;the influence of the temperature in the bore on the jet noise is relatively complicated,and the directivity of the sound pressure level is not very obvious.(4)Design a new type of double-hole device to suppress the muzzle flow hazard,so as to reach the safety protection standard of the weapon as much as possible.The analysis found that the dual-hole device can effectively suppress the over pressure in front of the muzzle side;the muzzle noise is attenuated significantly at a distance,and the noise at some locations is significantly reduced.