Experimental investigation of the hydrodynamic field around a half-cone woody debris jam on a bridge pier

ABSTRACTA debris jam causes extra load and associated scour on a bridge pier, and this significantly affects the safety of the bridge. Laboratory experiments were conducted to investigate the flow field around half-cone shaped debris jams of equal size, following the geometry in previous field studies, but with different surface roughness. The debris jams were assembled using dowels or by 3D printing. The results indicate three zones were observed behind the debris jam: the wake dead zone, high shear transition zone, and accelerated high-speed zone. A debris jam enlarges the dead zone while Reynolds shear stress was greatest in the transition zone for all debris jam cases. Additionally, the drag coefficient of debris jams built by dowels was greater compared with the 3D-printed debris jam, attributed to the debris jam roughness. In summary, debris jams form the wake dead zone behind the pier, increase downward flow in front of the pier, and enhance flow acceleration around the pier, highlighting the potential hazards to bridge safety.Keywords: Debris jamdrag coefficientflow fieldReynolds shearsingle pier Supplemental dataSupplemental data for this article can be accessed online at https://doi.org/10.1080/00221686.2023.2259859.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe first author would thank the joint financial support provided by the China Scholarship Council and the University of Ottawa. Additional fundings from the NSERC Discovery grants held by Colin Rennie and Ioan Nistor are also acknowledged.