Investigation on local scour downstream of adverse stilling basins

This paper is focused on local scour downstream of adverse stilling basins where a submerged wall jet issued from a sluice gate. Experiments were conducted in a wide range of Froude numbers, grain sizes, tailwater depths, and stilling basin slopes. The results showed that the scour profiles at any bed slope follow shape similarity. However, the longitude evolution of scour profiles and the volume of eroded materials were increasing in accordance with slope of basin. A polynomial equation was derived to define the non-dimensional profiles under different slopes. The time evolution of scour hole dimensions and the equilibrium state were defined. It was found that under a specific condition of sediment grain size, approaching Froude number, the length and slope of adverse basin, the scour depth at the downstream of adverse basin, initially increases with tailwater depth, and after reaching its maximum value decreases to a constant value. It was also observed that the maximum depth of scour hole was decreased as the length and slope of stilling basin increased, whereas the longitudinal dimensions of the hole were increased. It was found that the maximum depth of scour hole occurs at the vicinity of side walls with slight decrease in the centerline. Finally, a power equation was expressed to fully define the dimensions of scour hole, time scale and geometry of sluice gate.