Drag Reduction with Optimum Designing of a Base Bleed Projectile Using Computational Analysis

Abstract

Artillery guns are deployed at different gun positions to give cover to ground forces during offensive and defensive operations. All these guns have a specific target area which is limited by the type of ammunition, gun, and terrain. During offensive operations, there is an imperative need to change the target area with the advancement of ground forces. This entails changing of gun positions for increasing the range of fire which can be a cumbersome task especially in mountainous terrain where mobility and time are of paramount importance. The muzzle velocity of the gun is reduced when guns fire at a high angle of elevation akin to conditions prevailing in hilly terrain. Thus providing a scope to reduce drag and increase the range in the necessary operating conditions. This study aims to validate and computationally alter the design of the ammunition for further drag reduction while retaining its property to be fired from the same gun with equal lethality and increased range. Drag reduction for projectiles and missiles is undertaken in every possible way to increase the range of target engagement and support the ground forces. Computational analysis has been conducted on the exterior ballistics of a 155 mm M864 artillery shell for reducing its base drag. The investigation and analysis are carried out for the projectile with and without injection. Projectiles with base bleed reduce the base drag through burning solid propellant into the base area. After validating the case for different Mach numbers, the projectile is subjected to change in boat-tail angle for further drag reduction. A higher drag reduction is obtained by the combination of boat tail and base bleed. The boat-tailing aid in reducing the base drag as the base area gets reduced, thus reducing the wake region. The maximum boat-tail angle will vary for different Mach numbers, and based on the operating conditions, a maximum angle can be reached to achieve an optimum design. This may lead to up to 15–20% base reduction and an overall increase in the range up to 2–4 km. Numerically altering the boat-tail angle would lead to a drastic reduction on the logistics of testing and designing the ammunition for military requirements.