عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Vanes are rectangular thin angled flow-training structures produce high and low pressure zones on two sides of them. These structures generate a secondary vortex, which is used to modify the near-bed flow pattern and thus redistribute the sediment transport and erosion within the channel cross section. The function of vanes to reduce scour around the bridge piers and sediment movement in the region of vanes due to downflow in front of them will be affected by arrays of the vanes. This research reports on a laboratory study that examines the effectiveness of submerged vanes as a pier scour protection devices. Experiments were conducted in an 8m long and 0.8m wide flume and a cylindrical pier of 6 cm diameter was used. Clear-water scour tests with u*/u*c=0.9 were performed with two different vane aspect ratio (length to height of 2 and 3), and one placed at streambed level. Dissimilar arrays of vanes with different angles to main flow direction were employed. The results showed that reduction of scour with different arrays of six vanes was 0.4% to 51%. The highest reduction was occurred in the layout of each row of vanes with different angles. In the case of application of four vanes, scour depth was reduced to 12%. The reduction for two vanes was 1% to 5%. Finally, application of six vanes in the layout of each row with different angles was the best case of scour reduction around the bridge piers in this research.