Experimental and numerical investigations on the performance of sacrificial piles in reducing local scour around pile groups

This paper presents both experimental study and numerical simulation to investigate the effects of an innovative sacrificial piles concept to reduce local scour surrounding service piles. These sacrificial piles are placed upstream of the pile groups, which serves to change the flow field and reduce the erosive force before it reaches the service piles. Four types of pile group arrangements were considered in the experimental and simulation analyses, including single pile, double pile in tandem arrangements, double pile with side-by-side arrangements, and pile array of 2 × 2 arrangements. Scaled experiments were conducted in flume for each group of design, and local scour around piles with and without sacrificial piles was monitored. It was found that the sacrificial piles effectively reduced the development of local scour surrounding the service piles, especially at their heels. The results also showed that the use of sacrificial piles reduced the time required for the scour depth to reach the equilibrium conditions than those without the sacrificial piles. To corroborate the experimental observation, numerical simulation with three-dimensional computational fluid dynamics model has also been carried out with commercial code with verified erosion model. The development of dynamic scour process and maximum scour depth were obtained by the computational simulations. Comparison of experimental and computational results both indicates that the use of sacrificial pile is effective in reducing the scour depth. The extent of reduction in the maximum scour depth varied with the arrangement of sacrificial piles.