The Effect of Combination of Footing and Triangular Weirs on Bed Topography in a 90º Mild Bend

Abstract

Triangular weirs (Triangular vanes) and footing are measures which causes to control the scour in outer bend and keep out scouring hole from the outer bend. In this study, the main purpose is to experimentally study the effect of using both footing and triangular weirs on sedimentation and erosion of a bed of flume bend under different flow conditions (Froude numbers 0.243, 0.262, 0.292 and 0.321). Tests were conducted using triangular weirs with distance of 8 times of the effective length installed at an angle of 30 degree from the upstream bank. Footing width and effective length of triangular weirs were selected one-fifth the width of the canal. The results showed that using footing combined with the triangular weirs caused to reduce maximum scour depth at the toe of weirs and prevent from its extension to outer bend. Using footing reduced 70 percent maximum scour depth at the toe of weirs. Moreover using footing combined with triangular weirs had a little effect on flow diversion from outer bank towards the center of flume. The results show that using footing along with triangular weirs increased 9 percent maximum scour depth of thalweg and did not change the thalweg distance from the outer bank.

Keywords

• footing
• triangular weir
• triangular vanes
• banks erosion
• river bend