To reduce the drag coefficient, we reviewed the data of the separation and reattachment that occur on the surfaces of the moving bodies. According to this review, we think that the size of the separation bubble in the wake of the moving body plays an essential role in controlling the drag value. We suggested some geometry modifications that may decompose the large scale separation bubbles behind the moving body into smaller bubbles. The effects of these modifications on the drag were tested experimentally and numerically for a base-line truck and the standard target, 7.62 × 39. First, we replaced the truck edges by curved surfaces and that produced about 4% drag reduction. Next, we tried to rotate the curved surfaces of the truck about its centerlines, but this technique slightly reduced the drag. Finally, we modified the back surfaces of the truck and the standard target, 7.62 × 39. with suggested features, and this last technique produced promising values of the drag reductions that ranged from 20% to 30%.

drag, separation, reattachment, truck, target, velocity.