Bend scour reduction induced by an air-bubble screen under live-bed conditions

Open-channel bends are characterized by complex interactions between streamwise flow, curvature-induced secondary flow and bed morphology. These bend effects cause erosion near the outer bank, and deposition near the inner bank. Previous laboratory experiments in a sharply curved flume with a mobile bed under clear-water scour conditions have shown that an air-bubble screen generated with a porous tube on the bed can counteract the curvature-induced secondary flow and lead to a shift of the maximum scour away from the outer bank. The here reported study provides experimental results on the optimization of the bubble screen under live-bed conditions. The air-bubble screen considerably reduces erosion near the outer bank for all investigated configurations of the bubble screen. Comparison of three different locations of the porous tube shows that the bubble screen is most efficient when placed very near to the outer bank.