Influence of pier-grid energy dissipator on energy dissipation and diversion characteristics of stilling basin in turning section

To investigate how the pier-grid energy dissipator (P-GED) mitigates adverse hydraulic effects caused by centrifugal force and flow inertia in bend sections, this study takes the turning-section stilling basin as the research object. A total of 27 P-GED schemes were designed using the controlled variable method. Based on the coefficient of variation of water surface superelevation and energy dissipation rate, three evaluation methods—Simple Weighted Method, Technique for Order of Preference by Similarity to Ideal Solution, and Entropy Weight Method—were applied for scheme selection. Subsequently, six indicators, including the water-depth adjustment coefficient of the concave and convex banks, flow velocity reduction ratio, turbulence intensity, and turbulence kinetic energy, were used to compare flow characteristics under conditions with and without P-GED. The results indicate that for energy dissipation, the influencing factors are ranked as pier height > pier length > grid height, whereas for flow guidance, pier length > grid height > pier height. The P-GED significantly increases water depth along the stilling basin, suppresses end wall overflow and fold flow, and enhances water surface uniformity by raising the water-depth adjustment coefficient of the concave and convex banks beyond 90% in the downstream region. The velocity reduction ratio in the P-GED arranged zone reaches 87.92%, an increase of 34.23% compared to the case without P-GED. Meanwhile, turbulence is significantly intensified, with longitudinal and lateral turbulence intensity increased by 358.82% and 280.00%, respectively, accelerating kinetic energy dissipation. These results provide reference for the design and safe operation of turning-section stilling basins.