Numerical Investigation of Hydraulic Characteristics Effective on Vertical Drop

The drops are used to control the descents,  stabilize the bed level, and control the upstream water level in sloping channels with less slope than the ground slope. The current study presents a numerical analysis of hydraulic characteristics in the vertical drop using computational fluid dynamics. At first, the laboratory models were used for verification and choosing the best model of turbulence; three types of turbulence models, k-ε, k-ε RNG, and k-ωwere used. The results revealed that the RNG k-ε turbulence model has less RE% and RMSE than other models and more efficiency in simulating hydraulic characteristics on drops. Also, it was observed that the highest rate of RE% and RMSE for this turbulence model was 6.18 and 0.109 for the relative length of the drop, whereas the lowest relative downstream depth was 5.27 and 0.003, respectively. Furthermore, by increasing the relative critical depth, the characteristics of relative downstream depth, the relative depth of the pool, and the relative length of the drop increased, whereas the relative energy dissipation decreased. For the parameter of the relative length of the drop in the range of 0.08 to 0.5, this increase was obtained to be 2.6 times. In addition, using numerical data, a series of equations have been presented to predict hydraulic parameters of the vertical drop with a high correlation coefficient.