DRAG REDUCTION FOR TURBULENT-FLOW OVER A PROJECTILE .2.

The performance of a secant-ogive-cylinder-boattail projectile in the transonic regime in terms of drag is numerically investigated. To impr ove the projectile performance, a drag reduction method, passive contr ol of shock/boundary-layer interaction on the boattail, is applied. Th e effectiveness of this method is studied by varying the values of par ameters such as porosity distribution, maximum porosity factor, and le ngth of porous boattail section. The present results show that the pas sive control method applied on the boattail not only can reduce the bo attail drag but also can reduce the base drag, and an additional 7% (a pproximately) total drag reduction is obtained compared with that with out the passive control. The passive control effect on total drag redu ction is found to be insensitive to Reynolds number.