Effect of Boattail Angle on Pressure Distribution and Drag of Axisymmetric Afterbodies under Low-Speed Conditions

This study is focused on the effect of boattail angle on the pressure distribution and drag force of axisymmetric afterbodies under low-speed conditions. Experiments were conducted on three conical boattails with angles of 10 degrees, 14 degrees and 20 degrees. The diameter-based Reynolds number is approximately 4.3 x 10(4) under the experimental conditions. Two types of flows, a fully-attached flow (beta = 10 degrees) and a flow with a separation bubble (beta = 14 degrees, 20 degrees), were observed. The aerodynamic drag measurements were conducted using both a strut-supported model and a support-free (levitated) model. The results show that boattail model with the angle of 20 degrees has a relatively large effect on the pressure distribution. The pressure drag resulting from pressure distribution on the vertical plane indicates that the model with a boattail angle of 14 degrees has the lowest drag. A good trend in agreement between afterbody drag (measured using pressure taps) and total aerodynamic drag (measured using the levitated system) was obtained. The effect of strut support on pressure distribution at different polar angles is also explained in this study.