A hooked-collar for bridge piers protection: Flow fields and scour

Su Chin Chen, Samkele Tfwala, Tsung Yuan Wu, Hsun Chuan Chan, Hsien Ter Chou

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


A new type of collar, the hooked-collar, was studied through experiments and numerical methods. Tests were conducted using a hooked collar of a width of 1.25b and a height of 0.25b, where b is the bridge-pier width. The hooked-collar efficiency was evaluated by testing different hooked-collar placements within the bridge-pier, which were compared to the bridge-pier without any collar. A double hooked-collar configuration, one placed at the bed level and the other buried 0.25b, was the most efficient at reducing the scour hole. In other cases, a hooked-collar positioned 0.25b above the bed slightly reduced the scour hole and had similar scour patterns when compared to the pier without the hooked-collar. The flow fields along the vertical symmetrical plane in the experiments are also presented. Laboratory experiments and numerical tests show that maximal downflow is highly reduced along with a corresponding decrease in horseshoe vortex strength for the experiments with the hooked-collar, compared to cases without the hooked-collar. The flow fields reveal that the maximum turbulent kinetic energy decreases with the installation of the hooked-collar.

Original languageEnglish
Article number1251
JournalWater (Switzerland)
Issue number9
StatePublished - 14 Sep 2018


  • Bridge
  • Collar
  • Hooked-collar
  • Pier
  • Scour


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