Bow-shock instability induced by Helmholtz resonator-like feedback in slipstream

Naofumi Ohnishi, Yosuke Sato, Yuta Kikuchi, Kiyonobu Ohtani, Kanako Yasue

研究成果: Article査読

4 被引用数 (Scopus)


Bow-shock instability has been experimentally observed in a low-γ flow. To clarify its mechanism, a parametric study was conducted with three-dimensional numerical simulations for specific heat ratio γ and Mach number M. A critical boundary of the instability was found in the γ-M parametric space. The bow shock tends to be unstable with low γ and high M, and the experimental demonstration was designed based on this result. The experiments were conducted with the ballistic range of the single-stage powder gun mode using HFC-134a of γ = 1.12 at Mach 9.6. Because the deformation of the shock front was observed in a shadowgraph image, the numerical prediction was validated to some extent. The theoretical estimation of vortex formation in a curved shock wave indicates that the generated vorticity is proportional to the density ratio across the shock front and that the critical density ratio can be predicted as ~10. A strong slipstream from the surface edge generates noticeable acoustic waves because it can be deviated by the upstream flow. The acoustic waves emitted by synchronizing the vortex formation can propagate upstream and may trigger bow-shock instability. This effect should be emphasized in terms of unstable shock formation around an edged flat body.

ジャーナルPhysics of Fluids
出版ステータスPublished - 2015 6月

ASJC Scopus subject areas

  • 計算力学
  • 凝縮系物理学
  • 材料力学
  • 機械工学
  • 流体および伝熱


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