Physical study of the 3-dimensional characteristics and free-surface properties of a breaking roller in bores and surges

Davide Wüthrich*, Rui Shi, Hubert Chanson

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

7 Citations (Scopus)

Abstract

Breaking surges and bores are observed during flood events, tidal bores and tsunamis propagating in rivers. The sudden increase in water depth generates an aerated and recirculating region, called the roller, whose turbulent behaviour is poorly understood. Based on ensemble-average analyses with multiple repetitions, this experimental work processed high-speed videos from multiple locations to characterise the spatial and temporal dynamics of the bore's roller. The results showed different air entrainment mechanisms for increasing Froude numbers, providing adapted formulae to predict the extension of the shear layer and the air-water boundary. Seen from above, the roller toe perimeter had an indented profile rapidly evolving in time, revealing a certain level of periodicity. A statistical analysis in terms of position of the roller toe, longitudinal fluctuations and instantaneous celerities allowed for a detailed characterisation of the turbulent surface fluctuations and three-dimensional properties of the breaking bore roller, leading to a better understating of the governing process.

Original languageEnglish
Article number109980
Number of pages13
JournalExperimental Thermal and Fluid Science
Volume112
DOIs
Publication statusPublished - 1 Apr 2020
Externally publishedYes

Keywords

  • Aeration
  • Bore celerity
  • Breaking bore
  • Open channel
  • Positive surge
  • Roller toe

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