Geometric characteristics of a cylindrical deflector above the end-sill of a stilling basin

The authors investigated the effect of the cylindrical deflectors over the end sill on minimizing or eliminating scour downstream of a stilling basin. Three different deflector parameters were investigated experimentally to determine the best performance: diameter, vertical placement above the end sill, and lateral position. A physical model was constructed and data were collected at the hydraulic laboratory of the University of Tabriz. The preferred vertical position above the end sill and optimal lateral location that gives the preferred performance of the deflector (minimum–scour) were determined to equal 0.85z and 0.5z (where z is the high of the end sill), respectively. The preferred deflector diameter was determined by installing the deflector at the preferred lateral and vertical locations. The preferred deflector diameter was determined to be 0.5z. Finally, a deflector with the preferred diameter was studied at the preferred location for Froude numbers from 4–8. The results showed that using a cylindrical deflector with the appropriate diameter in the appropriate location can reduce scour depth and length by 78% and 68%, respectively. Finally, based on the dimensional analysis, a relationship was presented to estimate the maximum relative scour depth downstream of a stilling basin with a cylindrical deflector. © 2023 Indian Society for Hydraulics.