Start Date

6-29-2016 1:30 PM

End Date

6-29-2016 3:30 PM

Abstract

Stepped spillways are characterised by highly turbulent air-water flows and a large rate of energy dissipation compared to smooth chutes. Herein detailed measurements were performed in both the developing non-aerated and fully-developed air-water flow regions on a large 1V:1H stepped spillway model. In the developing flow region, large total pressure fluctuations and turbulence intensities were recorded next to the pseudo-bottom. Downstream of the inception point, large total pressure fluctuations were recorded which were mainly induced by density fluctuations. The water turbulence intensities in the air-water flow region did not differ significantly from those in the developing flow region. The steps generated significant form loss, amounting to about 50% of the upstream total energy regardless of discharge. Similar rates of energy dissipation and friction factors were found between the developing non-aerated and fully-developed air-water flow regions. The energy dissipation on stepped chutes was found to be sensitive to the chute slope, and relatively little affected by the air-bubble diffusion.

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Jun 29th, 1:30 PM Jun 29th, 3:30 PM

Turbulence and Energy Dissipation in the Developing Non-Aerated and the Fully-Developed Aerated Flows on a Stepped Spillway

Portland, OR

Stepped spillways are characterised by highly turbulent air-water flows and a large rate of energy dissipation compared to smooth chutes. Herein detailed measurements were performed in both the developing non-aerated and fully-developed air-water flow regions on a large 1V:1H stepped spillway model. In the developing flow region, large total pressure fluctuations and turbulence intensities were recorded next to the pseudo-bottom. Downstream of the inception point, large total pressure fluctuations were recorded which were mainly induced by density fluctuations. The water turbulence intensities in the air-water flow region did not differ significantly from those in the developing flow region. The steps generated significant form loss, amounting to about 50% of the upstream total energy regardless of discharge. Similar rates of energy dissipation and friction factors were found between the developing non-aerated and fully-developed air-water flow regions. The energy dissipation on stepped chutes was found to be sensitive to the chute slope, and relatively little affected by the air-bubble diffusion.