Flow and Turbulence Structure around Abutments with Sloped Sidewalls

Abstract

AbstractResults of eddy-resolving numerical simulations are used to investigate flow and turbulence structure around an isolated abutment with sloped sidewalls at conditions corresponding to the start (flatbed) and the end (equilibrium bathymetry) of the scour process. Besides cases where the abutment is not protected against scour using riprap, the paper considers cases where a riprap apron of constant width is present around the base of the abutment at the start of the scour process. The paper also discusses the effect of large-scale turbulence (e.g., horseshoe vortex system, eddies shed in the separated shear layer, vortices forming in the recirculation regions) on sediment entrainment and transport. Using information about the position and coherence of the large-scale turbulent structures present in the vicinity of the bed surface, the paper discusses some of the reasons for the very different bed scour patterns observed at equilibrium scour conditions for cases without and with a riprap apron. The ef...