numerical simulation and operation comparison of two sizes of air gun pellets with 4.5 and 5.5 mm calibers

in this paper the numerical simulation and operation comparison of two sizes of air gun pellets with 4.5 and 5.5 mm calibers is performed. these pellets affected by drag force and are encountered to continuous velocity variations and experience an unsteady flow. in order to solve this problem numerically, the navier- stokes equations in an unsteady compressible turbulent flow with the dynamical equations of pellet motion solved simultaneously in a moving computational grid by a computer code. the geometrical modeling of pellets is obtained by accurate photography of actual sample and digitization. according to pellets geometry, the axisymmetric cylindrical coordinate system is used. the numerical simulation is based on discretization of convective flaxes by second-order central difference scheme and an implicit finite volume method. because of the time importance in solution, the second-order time accurate is applied by dual time stepping approach. then, in order to validate the operation of computer code the results are compared with experimental data. the results obtained from this investigations show that the shoot velocity, mass and pellets size are the effective factors on trajectory time, height loss and hitting momentum at a certain distance.