Local scouring is considered one of the main causes of bridge failures. It occurs due to horseshoe vortex (HSV) formation that enhances the shear stresses resulting in sediment removal and therefore scours hole development. To study such a phenomenon, LES was conducted by Schanderl (2018) at Re = 20,520 and Re = 41,509. For each Reynolds Number, five simulations were conducted using different grid resolutions, which helped in performing a convergence study. The simulation quality was assessed also by investigating the inflow profile and the sub-grid scales effect. The latter had a negligible contribution (νt = 0.22ν) where most of the important scales were resolved. The flow topology was analyzed along with the velocity at the symmetry plane. The HSV was visualized, and its center and core-line were found. The minimum pressure criterion used to iden- tify the HSV center showed a good agreement with the LIC surface and Sujudi and Haimes method. It was concluded that the flow topology is independent of Reynolds Number; however, the latter has an insignificant effect on the HSV center and core-line. This analysis helped in understanding the time-averaged behavior of the HSV while the instantaneous flow field was analyzed using the Q-criterion and the pressure field, which showed the unsteady behavior of the HSV. Moreover, the velocity was plotted at different locations to understand the velocity variation inside the scour hole along with the adverse pressure gradient effect and the down-flow behavior. Furthermore, the turbulent kinetic energy (TKE) was studied where it had a c-shape structure with a maximum at the HSV center similar to the one observed in the flat-bed case. Nevertheless, the TKE production was investigated where the detached layer and decelerating region were feeding the HSV with TKE while the dissipation rate had a similar distribution to the TKE. Finally, the wall shear stress was studied and its behavior was related to the flow topology. A comparison to Jenssen (2019) experiment was made, and a good agreement was achieved.     «

Local scouring is considered one of the main causes of bridge failures. It occurs due to horseshoe vortex (HSV) formation that enhances the shear stresses resulting in sediment removal and therefore scours hole development. To study such a phenomenon, LES was conducted by Schanderl (2018) at Re = 20,520 and Re = 41,509. For each Reynolds Number, five simulations were conducted using different grid resolutions, which helped in performing a convergence study. The simulation quality was assessed al...     »