EXPERIMENTAL INVESTIGATION OF SUBMERGED VANES AS ANTIBANK EROSION MEASURES•

Abstract

One of the most striking and intriguing features of natural alluvial streams is their tendency to meander. In addition to being a fascinating natural phenomenon and posing some of the nettling problems in the realm of river mechanics, river meandering, and in particular the bank erosion attendant to the growth and migration of the meander loops, has become a major challenge to river engineers for stream bank protection. For the detailed design of the bank erosion, -it is logical to look into the devices controlling the bank erosions. Among such devices, submerged vanes are frequently used devices that have several applications such as protection against bank erosion, exclusion of sediment from water intake structures and increasing navigational depth. The vanes are vertical small aspect ratio structures (foils) installed on the river bed and set with an angle of attack to the flow. They are designed to modify the near-bed flow pattern and redistribute flow and sediment transport within the channel cross section. The vanes function by generating secondary circulation in the flow. The circulation alters magnitude and direction of the bed shear stresses and cause a change in the distribution of velocity, depth and sediment transport in the area affected by the vanes. The effectiveness of a vane to generate the secondary circulation is dependent upon its height, depth, shape and the angle of attack of the approach flow. And when the vanes are kept in series along the river the area affected by the vane depends upon the vane spacing. However, there seems less information on sediment redistribution at low and high vane angles and longitudinal spacing of the vane arrays.