عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Local scour around the bridge piers results from the flow impact with bridge piers and it’s streamline separation. The scour hole around the bridge piers depend on the hydraulic characteristics of the flow, the specifications of the fluid, the pier’s shape and the size of the bed material. In most experimental study on scour around the bridge piers only one size of bed material is used. In this study the local scour around the cylindrical bridge piers with diameters of 10, 20 and 40 mm are measured and analyzed in a laboratory flume. The flow condition was clear water with relative velocities of 0.95, 0.86 and 0.76. Two uniform bed materials with mean diameters equal to 0.5 and 0.7 mm are used. The results indicated that in the constant hydraulic conditions for all piers diameters, the equilibrium time for maximum depth scour increases as the grain diameter of bed material increases. Also as the bed material increases from 0.5 mm to 0.7 mm, the depth of scour hole decreases when the diameter of pier was 40 mm and the relative velocity was 0.95 and also when the pier diameter was 10 mm and the relative velocity was 0.76. The amount of scour depths decreases for above mentioned piers were equal to 1.2 times and 4 times respectively.