Drag Reduction of Afterbodies by Controlled Separated Flows

The zero-lift drag characteristics of a class of multistep afterbodies that utilize the concept of controlled separated flows are documented at transonic and supersonic speeds. The important geometrical and flow parameters affecting the drag of such afterbodies are identified, and their effects are examined through a parametric study. The results show that multistep afterbodies can be designed that provide significant total drag reduction (as high as 50%) compared to (unmodified) blunt bases; however, compared to axisymmetric boattailed afterbodies of a given base area, the multistep afterbodies have relatively higher drag. Finally, the certain flow features involving separation and reattachment on multistep afterbodies are discussed based on flow visualization studies