Experimental Investigation on the Effect of Slotted Triangular Vanes

Abstract

Investigations have indicated that in-stream structures have better performance rather than alternative structures such as rip-rap revetment and spur-dikes in term of cost, performance, maintenance, and environmental enhancement and help preserve the environment on the banks of meandering rivers. The slotted triangular vanes are among the in-stream structures. This study aimed at investigating the effect of slotted triangular vanes in sedimentary channels bed variation in 90 degrees bend flume (R/B=4, R and B, bend radius and width of the flume, respectively). The experiments were performed by three distances of four, six, and eight times the effective length (Le) in Froude numbers of 0.287, 0.304, and 0.322 under clear water conditions. The bed materials used were sand with an average diameter (d50) of 1.5 mm and a geometric standard deviation ratio (σ) of 1.22. The vanes angle to the upper bank was constant. After conducting analysis, the bed topography and required data were collected. The results showed that by installing the vanes attached to the outer bend flume, local scour occurred at the tips of vanes. By increasing distance between the vanes, the average depth of scour around the tips of vanes increased so that the distance of 4Le presented better performance than the distance 6Le and 8Le in scour protection around vanes. The Scouring bed materials were precipitated on the back of vanes and near outer bank. By increasing distance between the vanes and increasing space between the vanes, scouring bed materials allocated more flume along the length; hence, the maximum mound height decreased.

Keywords

• bed topography
• instream structures
• sediment
• banks protection