Numerical Investigation of the Aerodynamics and Stability of a Flared Afterbody for Axisymmetric Projectiles at Supersonic Speeds
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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A parametric study has been conducted for eight similar axisymmetric, spin stabilized projectile shapes. The aerodynamic and stability parameters of flared projectile afterbodies at freestream Mach numbers of 2,3 and 4 and at an angle of attack of 2 deg have been determined. The projectiles under investigation has an ogive nose, a cylindrical midsection and one of three afterbodies an extended cylinder, a boattail conical frustum, and a boattail- flare two conical frustums end to end. Total projectile lengths of 6 and 7 calibers have been studied. Finite difference solutions of the Navier-Stokes equations, the method of characteristics, and semi-empirical models are used to predict normal force, static pitching moment, total drag, Magnus moment, roll damping and pitch damping. Estimations of gyroscopic and dynamic stability parameters are then made. This study determined that the boattail-flare renders the ogive nose and cylindrical midsection projectile configuration more gyroscopically and dynamically stable than the conventional boattail afterbody. Results also showed that the boattail-flare afterbody decreases the Magnus moment but increases total drag therefore providing a stability advantage at the expense of reduced range. This stability advantage can be utilized in long spin- stabilized projectiles as well as long rod penetrators where fin stabilization has been replaced by a boattail-flare. Future work may be aimed at utilizing present computational techniques as a design tool in the use of a flared afterbody for stable, reduced range projectiles.
- Ammunition and Explosives
- Fluid Mechanics