New Equations for Energy Dissipation down a Stepped Spillway

Stepped spillways use their stepping nature to substantially dissipate energy in floodwater. Many researchers investigated the hydraulic and geometric relationships of the stepped spillway with a dam slope above 26.6o degrees that resulted in energy dissipation. But few studied stepped spillways with a dam slope below 26.6o degrees that also resulted in energy dissipation with even fewer proposing models that estimated its energy losses. This resulted in limited information and guidelines for designers of stepped spillways involved with slopes below 26.6o degrees. The authors reviewed researchers' publications on horizontal stepped spillways with dam slopes between 3.4o ≤ θ ≤ 26.6o conducted in transition and skimming flows in large-size facilities with phase-detection intrusive probes. They obtained data sets from them, which they reanalyzed to develop 2 new energy dissipation models that govern skimming flows over a wide range of operating conditions. The data from the new models compared well with the measured data in terms of energy dissipation with high coefficients of correlation between 0.95 and 0.99. All data were in good agreement independent of channel slopes, stepped configuration, and sensor size. The models are simple, easy to use, and render more accurate results than the existing model.