Experimental and numerical investigation of scour around inclined pier group with sacrificial pile and collar

The scour has been studied in hydraulic science for many years, due to its complexity and lack of proper relationship, it has been the attention of hydraulic scientists. Hydraulic structures situated as an obstacle in front of water flow that changed the flow pattern in their vicinity and causing the local scour around the structure. There are various methods to reduce local scour around the pier. In this research, sacrificial pile and collar were used to reduce the local scour around inclined pier group. The results show that using of the sacrificial pile in front of the inclined pier group, the effect of the inclined pier angle on the reduction of the scour is lower. So that difference between the percentage of scour reduction for the first and second inclined piers in the angle of 5 and 15 degrees is zero and in vertical pier is 1.4%. The use of three collars with a diameter of 4b in pier group with the distance of 4b between piers and presence of sacrificial pile in front of the first inclined pier in distance of 3b compared to 2b show a greater scour depth reduction in front of the piers. In the numerical model, the use of inclined pier group with the distance of 3b between piers and sacrificial pile with distance of 2b shows lower turbulence intensity compared to distances of b and 3b.