Time evolution of uniform momentum zones in a turbulent boundary layer

A. Laskari, R. De Kat, R. J. Hearst, B. Ganapathisubramani

Research output: Contribution to journalArticleScientificpeer-review

29 Citations (Scopus)

Abstract

Time-resolved planar particle image velocimetry was used to analyse the structuring of a turbulent boundary layer into uniform momentum zones (UMZs). The instantaneous peak-detection method employed by Adrian et al. (J. Fluid Mech., vol. 422, 2000, pp. 1-54) and de Silva et al. (J. Fluid Mech., vol. 786, 2016, pp. 309-331) is extended to account for temporal coherence of UMZs. The resulting number of zones detected appears to follow a normal distribution at any given instant. However, the extreme cases in which the number of zones is either very high or very low, are shown to be linked with two distinct flow states. A higher than average number of zones is associated with a large-scale event in the log region which creates increased small-scale activity within that region. Conversely, a low number of zones corresponds to a large-scale event in the log region and decreased turbulent activity away from the wall. The residence times, within the measurement plane, of zones belonging to the latter scenario are shown to be on average four times larger than those of zones present during higher than average zone structuring states. For both cases, greater residence times are observed for zones of higher momentum that are generally closer to the free stream.

Original languageEnglish
Pages (from-to)554-590
JournalJournal of Fluid Mechanics
Volume842
DOIs
Publication statusPublished - 2018

Keywords

  • Key words boundary layer structure
  • turbulent flows

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