Evaluation of the simultaneous combination of bed sill and sacrificial piles in the reduction of local scour depth around the bridge pier and three-dimensional analysis of turbulent flow structure around them

Abstract

Abstract In the present experimental study, the simultaneous use of bed sill and sacrificial piles around the cylindrical bridge pier was studied, to investigate whether the combination of these two countermeasures could be effective in reducing scour depth. Toward this goal, 14 experiments were conducted. Since it is important to understand the state of sediment entrainment around the pier, the coherent turbulent flow structure around the best combination of bed sill and sacrificial piles was investigated and its effect on the bed scouring pattern was studied. The results related to the flow structure in the unprotected pier were considered for comparison. It was found that the simultaneous use of bed sill and sacrificial piles was completely effective in the control and reduction of local scouring and in the best configuration, it reduced the scour depth by 51.1%. Therefore, the use of this combination can be recommended to reduce the scour depth around the cylindrical pier. In this paper, 3D analysis of the bursting process (octant analysis) was used. Various characteristics of turbulence, such as turbulent kinetic energy, Reynolds shear stress and occurrence and transition probabilities of bursting events, were calculated. Investigating the sediment entrainment around the pier with bed sill and sacrificial piles confirmed the reduction of the scour depth by the combination of these two countermeasures.