Influence of small wavy roughness on flatplate boundary layer natural transition

Hiroki Tameike, Aiko Yakeno, Shigeru Obayashi

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


One of the effective ways to reduce viscous drag around an airfoil is by delaying the boundary layer transition. In this study, we analyzed the influence of a small wavy roughness on a two-dimensional, natural boundary layer transition, using direct numerical simulation that resolved each small roughness. A parametric study was conducted on the wavy roughness wavelength. Our results show that in some cases the transition delays whose characteristics depend on the roughness wavelength. In a detailed analysis, we found that the wavy roughness firstly affects the process of primary vortex growth, Tollmien–Schlichting (TS) instability. In addition, we found that the secondary vortex pairing also depended on it. In the most transition-delayed cases, the roughness wavelength was different far from the TS instability one, and the vortex pairing occurred firstly in upstream however not much in downstream, keeping the vortex size is kept small.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalJournal of Fluid Science and Technology
Issue number1
Publication statusPublished - 2021


  • Direct numerical simulation (DNS)
  • Laminarization
  • Surface roughness
  • Transition
  • Vortex paring

ASJC Scopus subject areas

  • Mechanical Engineering
  • Fluid Flow and Transfer Processes


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