Spatio-temporal analysis of the turbulent flow in a ribbed channel

Filippo Coletti, Irene Cresci, Tony Arts

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

The turbulent flow in a channel with transverse ribs over one wall is studied experimentally. The height of the obstacles is about one tenth of the channel height, and the spacing is 10 times their height. The Reynolds number based on the channel hydraulic diameter and bulk flow velocity is 15,000. Velocity fields are obtained with high spatial and temporal resolution along the streamwise/wall-normal plane by means of time-resolved particle image velocimetry. Beside mean velocity and Reynolds stresses, the flow is investigated through two-point correlations, distributions of spanwise-swirling events, space-time velocity diagrams and power spectral density. Although the separated flow reattaches before the following obstacle is approached, a strong rib-to-rib interaction occurs. Spanwise vortices, 0.2 rib heights in size, are generated in the free shear layer, travel across the whole pitch, and may impact on the next rib. The large scale motions triggered by the separation grow in size until they reach the following obstacle. Flapping of the separated shear layer is observed at frequencies consistent with previous studies, causing the instantaneous reattachment point to fluctuate. The flapping initiates at the downstream edge of the obstacle tip, rather than at the upstream edge where the instantaneous separation occurs.

Original languageEnglish (US)
Pages (from-to)181-196
Number of pages16
JournalInternational Journal of Heat and Fluid Flow
Volume44
DOIs
StatePublished - Dec 1 2013
Externally publishedYes

Keywords

  • Ribbed channel
  • Separating/reattaching flow
  • Shear layer flapping
  • Spanwise vortices
  • Time-resolved PIV

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