Mechanism of drag reduction by pre-determined spatio-temporally periodic control of wall turbulence

Aiko Yakeno, Yosuke Hasegawa, Nobuhide Kasagi

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

We evaluate pre-determined controls with temporally- and spatially-periodic spanwise velocity inputs at the wall in a fully developed turbulent channel flow. The spatially-periodic control generally achieves better performance than the temporally-periodic one, which is conventionally called the spanwise wall-oscillation control. Particular attention is paid to the Reynolds stress, which dominates the skin friction. We apply a conditional sampling technique in order to clarify the response of the Reynolds stress around a particular rotation direction of a longitudinal vortex to the spanwise control input. Quadrant analysis of the Reynolds stress shows that the phase-dependencies of Q2 and Q4 events around a longitudinal vortex are totally different. Based on this knowledge, the drag reduction mechanisms in the two controls are discussed.

Original languageEnglish
Pages (from-to)555-562
Number of pages8
JournalNihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
Volume76
Issue number764
DOIs
Publication statusPublished - 2010 Apr
Externally publishedYes

Keywords

  • Coherent structure
  • Flow control
  • Friction drag reduction
  • Wall turbulence

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanical Engineering

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