دانشگاه فردوسی مشهد
In this paper, a numerical solution of the Navier-Stokes equations has been considered using Jameson method in a transonic flow over three air gun pellets. Furthermore, obtained aerodynamic results have been used in order to analyze the trajectories of the projectiles dynamically. The considered pellets have the same caliber of 4.5mm, but different nose shapes. The first pellet is a wadcutter, while the two other ones are a sharp pointed and a domed head respectively. These pellets have been geometrically simulated by means of a precise photography and a digitizer software application for the accurate determination of the plots and grid generation purposes. The aerodynamic results contain the streamlines, drag and pressure coefficients as well as pressure and Mach contours. These results demonstrate how drag coefficient changes versus the Mach number of the free stream flow which is a key point for the governing equations of the projectile motion. Dynamic results, which consist of trajectory and the Mach reduction diagrams of the pellets in various Mach numbers, have been acquired and compared in various Mach numbers. Relying on these analyses, from both aerodynamic and dynamic points of view, the third pellet in a variety range of Mach numbers is the most dominant projectile; however, the selection of superior pellet between the first and the second one strongly depends on considered Mach numbers at which the pellet travels its effective range of fly. The first pellet has a better fly than the second one at low Mach numbers, while at Mach numbers close to 1.0 and more, the preferable pellet is the second one.