A time-resolved DPIV study of the unsteady character of the flow over a surface-mounted prism

P. P. Vlachos, M. R. Hajj

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Time resolved digital particle image velocimetry is used to quantify mean and instantaneous flow parameters in the separated flow over a surface mounted prism. Two-dimensional measurements at the mid-plane of the prism of the mean velocity magnitude, reverse coefficient, and vorticity are presented. The instantaneous variations of the vorticity field are also presented, giving quantitative proof of the extent of the unsteady character of the flow. The mean flow results show variations of the edge of the shear layer and the separation bubble as the Reynolds number is increased from 2500 to 16500. The instantaneous analysis showed a sequence of events that starts with the shear layer becoming unstable and an associated vortex rollup. The interaction of this vortex with the wall forms a reverse flow in the boundary layer on the topside of the prism and generates opposite sign vorticity. A comparison of the mean and instantaneous flow characteristics shows that the flow undergoes significant variations with time such that the concept of a mean flow that consists of a shear layer, a separation bubble and reattachment may be of limited physical significance.

Original languageEnglish
Pages (from-to)543-553
Number of pages11
JournalJournal of Wind Engineering and Industrial Aerodynamics
Volume90
Issue number4-5
DOIs
StatePublished - May 2002

Keywords

  • Digital particle image velocimetry
  • Flow separation
  • Surface-mounted prism
  • Wind engineering

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