Coefficient of Drag and Trajectory Simulation of 130 mm Supersonic Artillery Shell with Recovery Plug or Fuze
Defence Science Journal
NomeNclature C Do Coefficient of drag at zero yaw C D Coefficient of drag ρ Air density S Projectile reference area m Projectile mass V Velocity of projectile V x , V y , V z X, Y, Z components of velocity W Wind velocity W x , W y , W z X, Y, Z components of Wind velocity t Time Ѳ Elevation INtroDuctIoN Coefficient of drag is an important parameter in external ballistics. A 130 mm artillery shell at 943 m/s muzzle velocity in vacuum covers a maximum range of 90.7 km whereas in the presence of
... in the presence of air, its range reduces to 24 km. Therefore, the coefficient of drag plays a vital role in the case of range and depends strongly on the shape of the nose of the projectile. The two different kinds of projectiles considered here are 130 mm shell with recovery plug and 130 mm shell with fuze. At times, when flat-nosed firing plugs are substituted for ogive-shaped fuzes in a sea-based Proof Range, like PXE, to significantly increase the drag force and air resistance, to reduce the range, terminal velocity, and striking energy of the projectile, then these encounter much higher resistance while penetrating into the sea bed at the target area, thus making subsequent recovery process easier and quicker. Recovery of the shells is very much essential for post-firing inspection to dynamically evaluate it for its strength of design. The range tables (RTs) of 130 mm shell with recovery plug is not readily available to estimate the trajectory elements. The impact points are difficult to locate in the absence of range tables. Proper estimation of co-efficient of drag will be helpful in computation of trajectory elements and generation of range tables. Theoretical estimation of suitable range location is also needed for safe deployment of recovery, and observation teams for easy recovery of shells after firing. Therefore, RTs are essential and for the preparation of range tables, coefficient of drag is an important parameter. NumerIcal eStImatIoN oF coeFFIcIeNt oF DraG The objective of the present study is to estimate numerically the coefficient of drag and shock wave pattern at different Mach numbers for both 130 mm supersonic artillery shell with recovery plug and fuze. The yaw was assumed to be zero in both the cases. Analysis was done numerically with the help of software GAMBIT 2.2 and FLUENT 6.3. The estimated C D was used as an input parameter for simulation of trajectory elements. The numerical results were validated with experimental data recorded by tracking radar. Finally, comparison was made with the estimated C D of projectiles with two different nose shapes and the trajectory elements were found out for preparation of range tables. aBStract In the present study, the drag variation and trajectory elements estimation of a supersonic projectile having two different nose shapes are made numerically. The study aims at finding the coefficient of drag and shock wave pattern for 130 mm artillery shell fitted with recovery plug or with fuze, when travelling at zero angle of attack in a supersonic flow of air. The coefficient of drag (C D ) obtained from the simulation is used as an input parameter for estimation of trajectory elements. The numerical results, i.e., the coefficient of drag at different Mach numbers and trajectory elements are validated with the data recorded by tracking radar from an experimental firing. Based on numerical results and data recorded in experimental firing, the coefficient of drag in the case of the shell with recovery plug is 2.7 times more than for the shell with fuze. The shock wave in the case of the shell with recovery plug is detached bow shock wave, whereas in the case of a shell with fuze, the shock is attached. The results indicate that the coefficient of drag increases with detached shock wave and an increase in the radius of the shell nose. Good agreements were observed between numerical results and experimental observations.