Aeration, Flow Instabilities, and Residual Energy on Pooled Stepped Spillways of Embankment Dams

Abstract

Air-water flow experiments were conducted on some flat and pooled stepped spillways with slopes of 8.9º and 26.6º in transition and skimming flows. The study comprised the observations of the flow patterns, some characteristic air-water flow properties and energy dissipation performances. The air-water flow properties showed some differences in terms of interfacial velocity, bubble count rate and turbulence intensity between the stepped chutes for the two channel slopes. These differences were also reflected in the residual energy data highlighting a better energy dissipation rate for the pooled stepped spillway with slope of 8.9º. However, the air-water flows on the pooled stepped spillways exhibited some instabilities and a safe operation must be tested in physical testing. The flat stepped spillway appeared the preferable design in terms of energy dissipation and flow stability.

Simple Design Criterion for Residual Energy on Embankment Dam Stepped Spillways

“…The agreement between equations and experimental data is not shown since it has been presented previously . Felder and Chanson (2013) compared their correlation and data set (Eq. (1)) with several other formulas including Meireles and Matos (2009) and one by Hunt et al (2014).…”

Air entrainment and energy dissipation on Gabion stepped weirs

“…New experiments were conducted in a large size stepped spillway model at the University of Queensland, previously used by Felder and Chanson (2013) and Guenther et al (2013). The test section consisted of a broad-crested weir followed by ten steps with step height h = 0.1 m and step length l = 0.2 m. The chute width was W = 0.52 m. A pump controlled with an adjustable frequency AC motor drive delivered the flow rate, allowing an accurate discharge adjustment in a closed-circuit system.…”

Step cavity and gabion aeration on a gabion stepped spillway

“…Details on signal processing were documented in and Chanson and Carosi (2007). The signal processing followed the workflow of Felder (2013).…”

“…Most studies focused on the air-water properties in the skimming flow above step edges. Only a handful documented the flow properties in the steps cavities (Gonzalez and Chanson 2004, Felder and Chanson 2011, Felder 2013. Little data is available on gabion stepped spillway flows, besides Peyras et al (1992) and Wuthrich and Chanson (2014).…”