Computational Parametric Study and Live Firing Validation of Base-Bleed Exit Configuration

Abstract

Base bleed, along with boattailing, is widely confirmed to be an efficient technique for drag reduction of projectiles. It is believed that the flow pattern at the projectile base, hence the level of drag reduction, is dependent on the base-bleed exit configuration design. It was also shown that bleeding from annular slots overperformed that from a single central orifice. However, central orifices are required for practical issues and may not be completely eliminated. The effect of simultaneous bleeding from the central orifice and annular slots was not adequately explored before. In addition, the impact of annular slot design on level of drag reduction was not thoroughly clarified in the available open literature. The objective of the present study was to systematically address these two gaps. Following parameterization of the bleed exit configuration, a set of three-dimensional computational simulations are conducted to find the design that yields the maximum drag reduction. A set of live firing experiments are conducted to assess the validity of simulation results. Based on parametric study results, the impact of bleed exit configuration on base flow pattern, base pressure, and total drag coefficient is explained. The optimized bleed configuration was found to yield a further drag reduction up to 5% compared to the baseline configuration, including a single central orifice.