| Abstrakt: |
The study of energy dissipation and pressure fluctuation over the stepped spillway is necessary for safe flood passage without causing cavitation damage to the steps. The current study analyzes the impact of curvedness of tread of steps on energy dissipation and pressure magnitudes. Four spillway models having fourteen steps and a slope of 1:0.84 were created from Froude's number non-dimensional analysis of existing spillway of Khanpur dam Pakistan. In each model, treads were made curved depending on three angles of suspension, i.e., 30°, 60°, and 90°. The simulations were performed by software package FLOW 3D which uses the renormalization group (RNG) turbulence model for accounting the turbulence; 3D Reynolds-averaged Navier–Stokes equations, which included sub-grid models for air entrainment, density evaluation to capture variable density, and drift flux to cope with the drifting of fluid over the model; and the volume of fluid (VOF) method to capture free-surface flow over the stepped spillway for the flow rate of 0.0208–0.068 m3/s. Model validation was done by comparing the previously reported experimental findings with FLOW 3D results. From more simulations, it was found that curving the treads of steps can improve the energy dissipation up to 5–7% for lower flow rates like 0.0208 m3/s and 0.027 m3/s, while no increment was seen for higher flow rates. Also, curving the treads produces more negative pressure at the risers of the model. HLD (head loss distribution) along the steps showed that for a simple stepped spillway model, lower steps like steps 12, 13, and 14 are more involved in energy dissipations as compared to curved stepped spillway models where the energy dissipation is shifted to higher steps like step nos. 1, 2, 3, 4, and 5. [ABSTRACT FROM AUTHOR] |
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