Economical Optimization of Diverging Stilling Basins with Rectangular and Trapezoidal Sections

Stilling basins are one of the most common structures for energy dissipation of flow with high velocities downstream Hydraulic Structures. Among these basins, diverging basins with rectangular and trapezoidal Sections is an alternative choice of classical basin because of better hydraulic performance in order of sequent depth, and relative energy loss and also no need to transition structure. The aim of this research is to investigate the effect of diverging walls of stilling basins on the structural costs in comparison with classical basins using results of physical model of hydraulic jump in diverging rectangular and trapezoidal basins with side slopes 1:0.5, 1:1 and 1:1.5, diverging angels 3-9 degree and The Froude numbers of 2.6 and 9. The results showed that in case of diverging basins with rectangular sections, increase in divergence angle from 4-9 degree, causes increase in hydraulic jump efficiency about 10-29 percent and decrease in structural costs about 4-20 percent. In addition to, the results of optimization model that was solved with Genetic Algorithm showed that in trapezoidal sections, for the Froude numbers lower than 4, diverging angel 3 and side slope 1:0.5 has the best performance. Comparison of results showed that with increase side slope and divergence angle in the trapezoidal sections, the structural cost of basins increases because of increasing in the jumps length.