Research On The Firing Table Compiling Methods For Sniper Weapons Based On Computational Fluid Dynamics

Technicians have been using particle trajectory for small arms firing table compiling for a long time in China.Taking a projectile as a particle,it can not accurately describe the flying attitude of a projectile without considering its rotation around the center of mass.In order to meet the needs of modern warfare,it is urgent to develop high-precision firing table compiling methods.In this paper,we first obtain the projectile aerodynamic coefficients through simulation methods on the basic theories of computational fluid dynamics,then we calculate its firing table by means of 6 dimensional trajectory equations,finally we analyze the variation law of typical ballistic parameters.(1)We study all the forces and moments exerted on the projectile in detail.And we study six degrees of freedom trajectory equations in ground coordinates,as well as the initial conditions and the relational equations.(2)The methods of steady state simulation and transient simulation combining are used to calculate the aerodynamic coefficients of the projectile.Then we analyze the change regularity of different aerodynamic coefficients.All the other aerodynamic coefficients except the pitching damping coefficient could be obtained through steady simulation.In transient simulation,we set the changing law of the pitch angle of the projectile with time as the sine curve,and calculate the pitch damping coefficient values on each discrete time point.Then we extract the pitch damping moment coefficient from the discrete data sets by the harmonic separation method.(3)The change rules of different aerodynamic coefficients with the Mach number are not the same,but all have a sharp jump near Mach number 1.0.The change regulations of coefficients with the rotating speed the projectile are linear,from which reason we can choose only two representative points about the rotating speed when we calculate aerodynamic parameters of the similar projectile.The drag coefficient changes quadratically with the angle of attack.All the aerodynamic coefficients increase slightly with the increase of the altitude.(4)We solve the six degrees of freedom trajectory equations using four order Runge-Kutta method by using all the aerodynamic coefficients we get above.We can get the basic firing table for standard conditions and the correction table for nonstandard conditions.By comparing with the experiment data of the range,we get to know that without the consumption of weapons and ammunition,the parameter errors of the firing table are within 2.6%.Our method should be very economical and effective on the preliminaryestimation of the external trajectory in the projectile designing.In the range firing table compiling,we could also make full use of this method,do the parameter checking in accordance with the test data,and bring a great leap of the firing table compiling for sniper weapons.This method is an important supplement to the range firing table compiling.