Effect of submerged vanes in front of circular reservoir intake on sediment flushing cone

Abstract

Reservoir sedimentation is a long-term process with various risks, such as reduction of storage capacity, hydropower generation and flood control functions throughout a reservoir's lifespan. For reservoirs facing loss of function with severe deposition, sediment flushing is an approach to preserving long-term storage. Here, submerged vanes combined with pressure flushing operations are proposed to facilitate scouring of such deposition. Experiments with various submerged vane heights, inclination angles on the flow direction, spacing, and divergent and convergent arrangements were conducted to investigate the scour cone volume and removal efficiency. Results showed that two divergent submerged vanes at an angle of 20° on the flow direction and optimum vane spacing ratios removed the deposited sediment significantly. In the presence of the submerged vanes, final sediment flushing volume and efficiency increased by a factor of 48 compared to the reference test. Using the experimental results, three equations were proposed to estimate the scour cone dimensions (length, width and depth). Additionally, a non-dimensional equation was developed for estimating the scour cone volume, using a polynomial correlation with vane spacing. The results of this study recommend the best installation of submerged vanes for releasing deposited sediments in the region near the bottom outlets of reservoirs.