Base Drag Reduction of 2D Bluff Body by Using Tabs at Transonic Speeds

As base drag accounts for most of the total drag for spacecraft with a large base area, reduction in the base drag improves its aerodynamic performance. In the present study, a method using a pair of tabs normal to the base surface is proposed to reduce the base drag, and its effects on drag reduction are experimentally examined for a two-dimensional, simple bluff body with a large base area, the cross-section of which consists of a circular forebody and a rectangular afterbody, by changing the tab’s position and length. In addition, the flow fields around the model with/without tabs were visualized by the schlieren method with a high speed video camera, and CFD analysis was also made to supplement the experimental results. It was found that the tab method can remarkably increase the base pressure, which leads to a large decrease in the base drag. In the case where a pair of tabs with a non-dimensional length of 0.38 are installed at the base edges, the total drag is reduced by about 20.6% at a Mach number of 0.6 compared with that in the baseline case without tabs. Even when short tabs with a non-dimensional length of 0.07 are employed, about 10.0% reduction in the base drag is achieved. Thus, it was made clear from this study that the tab method proposed here is effective to decrease base drag in the transonic flow.