Time development of scouring around rectangular piers with submerged vanes

Scouring is considered as a destructive phenomenon and engineers have always attempted to estimate exact amount of this process. Different methods have been suggested as acountermeasure to control or slow down the process around the piers. Scouring is a time dependent process therefore time plays an important role in the development and destructionrates. In this study, development rate of scouring process around the round nose rectangular pierswith submerged vanes was investigated. Submerged vanes alter amount and direction of shear stress on the bed by producing secondary flow that leads the velocity, depth and sediment transport to be changed. Experiments were carried out with piers aligned and skewed at 5 and 10degrees to the flow direction and with submerged vanes at various arrangements. In the experiments using submerged vanes, two angles of attack namely 20 and 30 degrees and threevanes heights of 0, 1.25 and 2.5 cm on the bed were employed. The results showed that inaddition to control the scouring process in front of pier, submerged vanes also decrease the rate of scouring. Maximum reduction of scour depth was 45.47%, 39.76% and 27.78% for submerged vanes with height of 2.5 cm on the bed and skewed at 30 degrees to the flowdirection when the pier was aligned at 0, 5 and 10 degrees to the flow direction respectively

Keywords:

bridge pier , scouring , secondary flow , submerged vanes , time development