This study investigates base bleed configurations for reducing base drag on a boat-tailed 0.5-caliber projectile flying at M \(_\infty \) = 2.57. Using computational analysis validated against experimental data, three bleed jet locations (central, middle, and outer annulus) are examined using forced and natural bleed approaches. Results reveal that annular jets outperform central jets in maximum achievable base drag reduction. While central jets show optimal performance at I = 0.0148 with 32% base drag reduction, outer annular configurations achieve 38% reduction at higher bleed rates by modifying rather than eliminating the wake structure. The middle annulus configuration proves most effective in natural bleed implementations using multiple slots, delivering 31% base drag reduction while minimizing internal flow losses. Flow-field diagnostics reveal two complementary mechanisms. Peripheral jets thicken and flatten the separating shear layer, shorten and narrow the recirculation bubble, and weaken the recompression shock. The central jet raises core pressure directly without markedly altering the outer shear-layer path. Both strategies suppress near-wake turbulence, but the annular jets show superior performance by mixing the injected mass with the near-wake flow more efficiently. The study findings highlight that optimal base drag reduction relies on both the bleed coefficient and the placement of jets, with annular arrangements demonstrating improved overall performance. Natural bleed systems achieved slightly lower drag reduction than forced bleed. However, they eliminate the need for additional propellant mass and associated integration costs.
