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

The Hung Tran, Takumi Ambo, Taekjin Lee, Yuta Ozawa, Lin Chen, Taku Nonomura, Keisuke Asai

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Abstract: 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 × 10 4 to 8.89 × 10 4 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: [Figure not available: see fulltext.].

Original languageEnglish
Article number36
JournalExperiments in Fluids
Issue number3
Publication statusPublished - 2019 Mar 1

ASJC Scopus subject areas

  • Computational Mechanics
  • Mechanics of Materials
  • Physics and Astronomy(all)
  • Fluid Flow and Transfer Processes


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