Evaluation the effect of attack angle of submerged vanes on reducing scour caused by contraction strand (Case study: contraction to 30 cm)

When a hydraulic structure is placed on the river bed or on either side of a stream, river section is dropped and a contraction is occurred in river section that caused scouring process is exacerbated. In this condition, scouring process is taken place which is called contraction scour. Different methods have been proposed for the reduction and control of scouring, but still have not been to using of the submerged vanes in the reduction of contraction scour. Submerged Vanes are small structures that are installed in the river bed with a small angle relation to flow direction to modify the flow patterns in the river. The present study aimed to investigate the effect of attack angle of submerged vanes on reducing of contraction scour. Various experiments were carried out in a flume with 20 m length, 0.6 m width and 0.6 m height. Galvanized iron sheets with 10 mm thickness were used in other to creating contraction section. The width of contraction in this study is 30 cm. Submerged vanes were placed under three angles such as 10, 20, and 30 degrees relation to the cannel center and attached to the wall of cannel with 50 cm spacing from each other. All experiments were repeated with 3 discharges such as: 20, 30, and 40 lit/s. The result of this study shows that using of these submerged vanes is effective in reducing of contraction scour in each 3 angels. The most reduction in bed elevation is 61.56 percent occurred for 20 degrees angle of attack in 20 lit/s discharge.