Numerical investigation of the turbulent flow around a bridge abutment

Bridge failures are frequently related to phenomena of local erosion at piers and abutments; literature on this topic does not provide fully satisfactory formulations to evaluate the scour depth. Since a detailed definition of the flow can improve the comprehension of the phenomenon, a numerical study on the turbulent flow around an obstacle archetypal of an abutment is presented. The turbulent flow characteristics are investigated by means of Large Eddy Simulation, obtaining results both on the averaged flow characteristics as on the instantaneous ones. The averaged flow around the obstacle is structured as a highly three-dimensional system of vortex structures; instantaneous structures are characterized by high vortex intermittency. The shear and normal stress distributions on the bottom-wall are analyzed in comparison with experimental observations relative to erosion phenomena. The numerical simulations are consistent with experimental observations on flow characteristics around an abutment in flat-bed condition and provide details on its three-dimensional features and instantaneous behavior.