Structure of large-scale vortices and unsteady reverse flow in the reattaching zone of a turbulent separation bubble

Masaru Kiya, Kyuro Sasaki

研究成果: Contribution to journalArticle査読

242 被引用数 (Scopus)

抄録

This paper describes experiments concerning the structure of large-scale vortices and the unsteady reverse-flow properties in the reattaching zone of a nominally two-dimensional separation bubble formed at the leading edge of a blunt flat plate with right-angled corners. The experiment was performed in a wind tunnel with a constant Reynolds number 2.6 x 104(based on the main-flow velocity and the thickness of the plate). Split-film probes, being sensitive to instantaneous reversals of flow direction, were extensively employed. An important feature of this study is a judicious use of surface-pressure fluctuations as a conditioning signal to educe the structure of the large-scale vortices. Distributions of fluctuating-velocity vectors and contour lines of high-frequency turbulent energy in a few space-time domains are presented and discussed. The most economical interpretation of these space-time distributions is that the large-scale vortices in the reattaching zone are hairpin vortices whose configuration is sketched in the text. The unsteady flow in the reattaching zone is mainly governed by two agents; the motion of the large-scale vortices and the low-frequency unsteadiness. The unsteady flow is clarified in terms of the motion (in a space-time domain) of zeros of the longitudinal velocity close to the surface of the plate; the effects of the two agents on this motion are presented separately. On the basis of these results, a mathematical model of the unsteady flow in the reattaching zone is suggested and found to yield good comparison with measured reverse-flow intermittency and frequency of local-flow reversals. It appears that the separation bubble experiences shrinkage and enlargement in connection with the low-frequency unsteadiness and that the speed of shrinkage is much greater than that of enlargement. The strength of the large-scale vortices in the reattaching zone seems to be dependent on the phase of the low-frequency unsteadiness.

本文言語英語
ページ(範囲)463-491
ページ数29
ジャーナルJournal of Fluid Mechanics
154
DOI
出版ステータス出版済み - 5 1985

All Science Journal Classification (ASJC) codes

  • 凝縮系物理学
  • 材料力学
  • 機械工学

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