EFFECT OF SPACING OF SUB 1, ERGED VANES ON BED SCOUR AROUND RIVER BENDS

Abstract

In the last two decades, the use of submerged vanes has increased considerably compared with other traditional methods for sediment management in meandering rivers. This newly emerging noble technique of submerged vanes is found to be cost- effective option for tackling the various problems effectively as compared to the traditional techniques. Submerged vanes are vortex generating devices that counter the secondary flow generated due to the curved stream lines, and are, therefore, used to control the movement of sediments in the open channel at river bends, to protect stream bank against erosion, to reduce sediment entrainment from water intake structures, to correct shoaling problems in navigation channels etc. The submerged vanes are designed to modify flow patterns near bed and redistribute the flow and improve sediment transport within the channel cross section at lesser cost. The strength of circulation is profoundly influenced by the magnitude of the incident angle of the vane with the prevailing flow direction. All the previous researches on submerged vanes have been performed in either straight or mildly curved channels with single bend with bend angle in the range of 90° to 180°. Only a study by Sahadeo (2004) has been done in the curved channel having two consecutive meanders. Therefore, in the present work, performance of submerged vane in a channel bend having two meanders is undertaken. In this study, experiments were carried out in a curved channel having two consecutive meanders with vanes arranged in a single array fashion. The main aim of this dissertation work is to study the effect of various vane parameters like stream-wise centre-to-centre spacing (S,) and vane edge-to-bank distance (Sb) on scouring. With this in view, the experiments were carried out in Hydraulic Engineering Laboratory of the Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee, India. The set-up was constructed in the river model sand tray of the laboratory. Experimental program was organized in three phases corresponding to three discharges.