Numerical Analysis of Pressure Profiles and Energy Dissipation across Stepped Spillways Having Curved Risers

In this study, curved risers stepped spillways models based on the increasing angle of suspension were tested to check for improvement in energy dissipation and pressure distributions. Four fourteen-steps stepped spillway models with a slope 1:0.84 were selected, using Froude's number non-dimensional similarity. The risers of steps were made curved, based on three angles of suspensions, i.e., 30 degrees, 60 degrees, and 90 degrees. The simulations were performed by FLOW 3D software and by the turbulence model Renormalization Group (RNG) for discharges between 0.020 and 0.068 m(3)/s followed by the model calibration. The 3D Reynolds-averaged Navier-Stokes equations were solved, which included sub-grid models for air entrainment, density evaluation, and drift-flux, to capture free-surface flow over the stepped spillway. It was estimated that curving the risers increases the energy dissipation up to three percent for lower flow rates, whereas it has no significant impact on energy dissipation for higher flow rates. It was found that in simply stepped spillway lower steps dissipate more energy as compared to curved risers stepped where energy dissipation is shifted to higher steps. On the other hand, curved risers stepped spillways showed lower values of negative pressures as compared to the simply stepped spillway. It was seen that a higher energy dissipating step as experienced more negative pressures as compared to the lower energy dissipating step.