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Base bleed, in which gases are discharged at the base of projectile, is confirmed to be an effective drag reduction technique. Itis believed that the design of base exit can impact the pattern of gas bleeding and, hence, the level of drag reduction. The present study is aimed to address this dependence that was not clarified in previous studies by examining the reduction in drag acting on a projectile with two different base bleed exit configurations. The first configuration includes a central circular orifice while the other is modified to include a smaller central circular orifice and four annular slots with equivalent total area. Numerical simulations on 3‑D computational domain have been conducted to estimate drag and to explore the base flowfield for each configuration. The computational results at different Mach numbers have been compared with the mean drag based on range shooting for projectiles with both base configurations. In addition, different simulations have been performed to predict the real pattern of bleeding through the modified configuration based on the comparison with firing data at different Mach numbers.

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