Turbulent Drag Reduction by Uniform Blowing Over a Two-dimensional Roughness

Eisuke Mori, Maurizio Quadrio, Koji Fukagata

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Direct numerical simulation (DNS) of turbulent channel flow over a two-dimensional irregular rough wall with uniform blowing (UB) was performed. The main objective is to investigate the drag reduction effectiveness of UB on a rough-wall turbulent boundary layer toward its practical application. The DNS was performed under a constant flow rate at the bulk Reynolds number values of 5600 and 14000, which correspond to the friction Reynolds numbers of about 180 and 400 in the smooth-wall case, respectively. Based upon the decomposition of drag into the friction and pressure contributions, the present flow is considered to belong to the transitionally-rough regime. Unlike recent experimental results, it turns out that the drag reduction effect of UB on the present two-dimensional rough wall is similar to that for a smooth wall. The friction drag is reduced similarly to the smooth-wall case by the displacement of the mean velocity profile. Besides, the pressure drag, which does not exist in the smooth-wall case, is also reduced; namely, UB makes the rough wall aerodynamically smoother. Examination of turbulence statistics suggests that the effects of roughness and UB are relatively independent to each other in the outer layer, which suggests that Stevenson’s formula can be modified so as to account for the roughness effect by simply adding the roughness function term.

Original languageEnglish
Pages (from-to)1-21
Number of pages21
JournalFlow, Turbulence and Combustion
DOIs
Publication statusAccepted/In press - 2017 Oct 4

Fingerprint

drag reduction
Drag reduction
blowing
Blow molding
roughness
Surface roughness
Drag
Direct numerical simulation
Friction
Reynolds number
direct numerical simulation
Channel flow
friction
pressure drag
friction drag
Boundary layers
Turbulence
Flow rate
Statistics
turbulent boundary layer

Keywords

  • Direct numerical simulation
  • Drag reduction
  • Roughness
  • Turbulent boundary layer
  • Uniform blowing

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Turbulent Drag Reduction by Uniform Blowing Over a Two-dimensional Roughness. / Mori, Eisuke; Quadrio, Maurizio; Fukagata, Koji.

In: Flow, Turbulence and Combustion, 04.10.2017, p. 1-21.

Research output: Contribution to journalArticle

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