Experiments in Fluids

, 60:36 | Cite as

Effect of Reynolds number on flow behavior and pressure drag of axisymmetric conical boattails at low speeds

  • The Hung TranEmail author
  • Takumi Ambo
  • Taekjin Lee
  • Yuta Ozawa
  • Lin Chen
  • Taku Nonomura
  • Keisuke Asai
Research Article


The effect of Reynolds number on flow behaviors and pressure drag around axisymmetric conical boattails was experimentally investigated at low-speed conditions. Four conical boattails with slant angles of 12°, 16°, 20°, and 22° were studied. The Reynolds number ranged from 4.34 × 104 to 8.89 × 104 based on the model diameter. The global-luminescent-oil-film skin-friction measurement was employed to analyze the surface skin-friction topology. Quantitative skin-friction values at the centerline were obtained in this study. The results show that a separation bubble can be formed on boattail surfaces at angles from 12° to 20°. However, at a boattail angle of 22°, flow is fully separated near the boattail shoulder. The integrated afterbody pressure drag indicated that, at angles of 12°, 16°, and 22°, the Reynolds number has very small effect on the afterbody drag, while, at 20° the drag coefficient decrease was relatively large with increasing Reynolds number. We believe that this study provided the first results for a boattail angle of 20° and we observed that the size of the separation bubble decreased as the Reynolds number increased. The effect of the separation bubble on the pressure distribution was also examined in detail.

Graphical abstract



This work was supported by Kakenhi Grant 16H04582 from the Japan Society for the Promotion of Science and by Presto Grant JPMJPR1678 from the Japan Science and Technology Agency.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • The Hung Tran
    • 1
    Email author
  • Takumi Ambo
    • 1
  • Taekjin Lee
    • 1
  • Yuta Ozawa
    • 1
  • Lin Chen
    • 1
  • Taku Nonomura
    • 1
    • 2
  • Keisuke Asai
    • 1
  1. 1.Department of Aerospace Engineering, Graduate School of EngineeringTohoku UniversitySendaiJapan
  2. 2.TokyoJapan

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