Effect of abutment length on the bed shear stress and the horseshoe vortex system

River engineeringNumerical modelling in river engineerin

An investigation of scale effects in the flow past a vertical wall abutment

River hydrodynamicsInteraction with structure

Time Evolution of the Horseshoe Vortex System Forming Around a Bridge Abutment

Scour forming around an isolated bridge abutment with curved end is investigated in this study. Clear water scour experiments are conducted for an abutment in a 25 m long sediment flume at a Reynolds number of 45000. 3D scour patterns forming around the abutments are obtained using an array of acoustic transducers along a grid refined up to 1-2 cm spacing at different stages of the scour. Detached Eddy Simulation (DES) is performed at the same channel Reynolds number for flat bed case (initiation of the scour) and for two deformed bed cases (intermediate stages of scour). Incoming flow in the simulations were fully turbulent containing unsteady velocity fluctuations. Variations in the structure and intensity of the horseshoe vortex system are investigated. At the initial stage of the scour the main and secondary horseshoe vortices undergo aperiodic bimodal oscillations. Those oscillations cause the horseshoe vortices to induce large bed shear stress values beneath them. As the scour hole starts forming secondary necklace vortex, HV2, gets closer to the primary necklace vortex, HV1, and merges with it at a location close to the abutment tip. © 2010 American Society of Civil Engineers

Simulation of flow in an open channel bend of strong curvature using Detached Eddy Simulation

River engineeringNumerical modelling in river engineerin

Clear-water scour evolution at dual bridge piers

For the efficient design of bridge pier footings, computation of time-evolution of scour depth around bridge piers is essential. In this paper, a semi-empirical model is developed to estimate the temporal variation of clear-water scour depth at a couple of identical cylindrical uniform piers in tandem arrangement. The experiments are carried out using different pier size, pier spacing, and flow intensities. The model development is based on sediment continuity approach and volumetric sediment transport rate from the scour hole using a sediment pickup function. The model results are presented as design charts giving the relation between dimensionless scour depth and time for practical use. Results of the proposed model are in relatively good agreement with the experimental results, in the tested range.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author