| Siphons are spillways that transport water from an upper source to a lower downstream outlet and pass it over a small elevation without the use of any mechanical devices or additional power. They can also be used for flow control, automatically spilling water when a given headwater elevation is reached. Once primed, they have a very large discharge per unit width capacity. However, priming the siphon can be variable and the ability to prime quicker would be a benefit. This research completed a comprehensive review of the literature and evaluated the operation of siphon spillways using numerical modeling, specifically computational fluid dynamics with the commercially available software Flow-3D HYDRO 2022R2. Since siphons have complex two-fluid air/water flows, the numerical model was calibrated using published data. A parametric study was completed varying input parameters such as the air entrainment rate, turbulent mixing length, surface tension parameters, and air bubble size to evaluate the effect on the numerical priming. It was found that a larger entrainment rate coefficient and a smaller air bubble size had the greatest effect on the priming time. Once calibrated, the model was applied to a local power plant siphon, named Mile 28 siphon. The priming process of the siphon was documented to better understand its operation. An additional goal of this research was to improve the priming of a siphon spillway with the addition of a flexible membrane. Several different models were completed to approximate and simulate the flexible membrane concept. However, these models introduced difficulties with the pressure iterations and the addition of the flexible membrane approximations did not perform as intended. Therefore, this concept requires additional research such as physical testing. |