INFLUENCE OF AFTERBODY ROUNDING ON THE PRESSURE DRAG OF AN AXISYMMETRICAL BLUFF-BODY

The effects of rounding the aft edges of a blunt-based axisymmetrical bluff body with streamlined forebody are studied by means of surface-p ressure measurements, at Reynolds numbers (based on the model length) Re-L = 1.15 x 10(6) and Re-L = 2.88 x 10(6). The results show that for a certain of curvature a maximum in pressure drag occurs, connected w ith the variation of the pressures on the portion of the afterbody lyi ng inside the separated wake, and with the contribution of the suction peaks before separation. However, the behaviour of the drag is found to be significantly dependent on Reynolds number, while the forcing of the boundary-layer transition at a fixed upstream position produces a substantial decrease of the drag only for the lower tests velocity.