Numerical Simulation of Scour Depth Variation Around Vertical Wall Abutments

Evangelia Farsirotou, Nikolaos Xafoulis

The HEC-RAS one dimensional, free-surface numerical model was used to simulate bed formation in alluvial channels. Based on the hydraulic equations all the hydrodynamic parameters were firstly simulated and then a sediment transport simulation was performed. The model can compute the sediment transport using a hydrodynamic simplification, the quasi-unsteady flow assumption, which approximates a continuous hydrograph with a series of discrete steady flow profiles. The current research work aims to investigate scour depth variation in the region of vertical wall abutments. Numerical computations of scour depth variation around a vertical wall abutment are verified by comparing them with available measurements. Moreover the study reports experimental results of scour depth variation along the center flow line of a channel in the vicinity of a vertical wall abutment. The experimental measurements of bed variation for six different inflow discharges and three different abutment widths, after a specified flow duration, are graphically presented and can be used by other researchers in order to validate their simulations. Comparison between computed results and available measurements of scour depths is satisfactory along the center flow line as the numerical simulation is one dimensional. The one dimensional model gives an accurate estimation of the maximum scour depth near the obstruction and it is applicable for a safe design criteria for the assessment of bridge vulnerability which is very important in river engineering works.