Retrofitting Vertical Slot Fish Pass with Brush Blocks: Hydraulics Performance

Abstract

The mean and turbulent flow characteristics of a vertical slot fish pass, with and without brush blocks, were investigated at the Cataloluk Small Hydropower Plant on the Tekir River, located in the Ceyhan River Basin of Turkey. Within the scope of the project, three-dimensional velocity measurements were performed at different hydraulic conditions. The prototype flow measurements showed that by placing brush blocks and the substrate in the vertical-slot pool: (i) the maximum velocity observed downstream of the slot was reduced by 39%; (ii) the maximum lateral component of the Reynolds shear stress observed in the slot region was reduced by a factor of 3; and (iii) the spatially averaged resultant velocity was reduced by 20%. With brush blocks, the turbulent jet region was reduced and recirculation regions disappeared. Furthermore, the spatially-averaged lateral component of the Reynolds shear stress was 3.3 times higher than the spatially-averaged streamwise component of the Reynolds shear stress because of the lateral velocity gradient and mixing in the pool. The present findings will contribute to potential improvements in the non and less efficiently-functioning vertical slot fish pass and other fish pass types by adding brush blocks.