Discharge Flow Rate for the Initiation of Jet Flow in Sky-Jump Spillways

Abstract

The sky-jump spillway is an economical and effective solution to return water to a river, eventually complemented by a pre-excavated basin. However, an inappropriate design could endanger spillways and even the dam itself. For the design of a sky-jump it is necessary to evaluate the position and dimensions of the potential pre-excavated basin based on the characteristics of the water flow to be evacuated and the geometric configuration of the sky-jump. The jump of the water jet occurs when a certain flow rate is reached. This flow rate for the initiation of the jet flow determines the position of the impact area closest to the spillway. We propose a new formula for the determination of the flow rate for the initiation of the jet flow, which incorporates as a novelty the influence of the curvature of the flip bucket. A methodology for the direct determination of the flow rate for the initiation of the jet flow is also presented. The new formula and methodology, based on experimental laboratory work and numerical modeling, will support the designer to choose the energy dissipation way, in the riverbed or inside the flip bucket, for low and frequent discharge flows.

Dam Safety-Overtopping and Geostructural Risks

“…The impact area corresponding to high discharge flow rates is easy to determine because it is clear that the water jumps in the direction determined by the angle of the ski jump. Pellegrino et al [8] presented an experimentally verified formula and a complete method to estimate the minimum discharge that causes the jump to occur. For a discharge under that minimum value, water falls at the ski jump toe, which must be protected.…”

Efecto del diseño del trampolín de lanzamiento en presas sobre la erosión del cauce

“…Lo hará si la forma definida en superficie para el cuenco se solapa con el trampolín. Como el caudal es variable de unos episodios de avenida a otros, sería necesario estimar la posición y extensión de cuencos correspondientes a varios caudales: el del inicio del lanzamiento (Pellegrino, Toledo, Aragoncillo, 2020), el caudal máximo de avenida y uno o más intermedios.…”

“…-Nuevos ensayos de verificación de la metodología propuesta para el diseño del cuenco, necesarios para demostrar que la forma final y posición de cuencos podría ser la envolvente correspondiente a varios caudales: el de inicio de lanzamiento (Pellegrino, Toledo, Aragoncillo, 2020), el máximo y algunos intermedios.…”