Bilateral contraction of flow by blind dams on easily erodible soils

Abstract

Abstract In various parts of the Amudarya river, transverse dams are built for channel control and to protect riverbank from scouring. Studies were carried out in CAIRI laboratory to study the hydraulics of flow near structures (dams) on both sides of the channel, specifically spreading patterns of flow overtopping and its erosive capacity. Experiments carried out on 20m x 2m erodible model for discharge values Q = 10.0, 20.0, 30.0 l/sec, contraction degree of n = B/(B-b 0 ) = 0.33, 0.5, 0.67 and with the installation angle with respect to the streambank α = 60°, 90°, 120° gave specific results. Based on theoretical and experimental studies, relationships were obtained, which allow establishing the boundaries for flow division, velocity distribution along the width and length of flow, vortex length, distances between structures, as well as the values for backflow velocities along the streambanks, that can be used to construct velocity field in the dam impact zone. The obtained methods allow to get the full picture of a flow spreading beyond dams at the presence of backflow.