Abstract
In this study, the effect of the presence of bed-block roughness in an ogee spillway on energy dissipation and jet length is investigated. A series of experimental and numerical tests were conducted using an ogee spillway with block roughness on the bed without a flip bucket and with a flip bucket at different take-off angles (32 °C and 52 °C). To model the free-flow surface, the volume-of-fluid (VOF) method and turbulence model from RNG k–ε were used. Results indicated that the numerical model is fairly capable of simulating a free-flow surface over an ogee spillway; using block roughness on the spillway chute without a bucket, relative energy dissipation increased by 15.4% compared to that in the spillway with a smooth bed, while for the spillway with 32 °C and 52 °C buckets, it increased by 9.5%. The jet length for a spillway with a flip bucket and roughened bed decreased by 8% to 58% compared to that in a smooth bed. Lastly, the relationships for the estimation of relative energy dissipation and jet length are presented.
Highlights
Energy-dissipating structures are usually constructed at the end of spillway discharge channels in order to dissipate the extra energy
This study focused on comparing experiments and a numerical model of ogee spillways with flip
This study focused on comparing experiments and a numerical model of ogee spillways with dams, few works have focused on the effects of elements placed in the chute
Summary
Energy-dissipating structures (i.e., hydraulic jump stilling basins, roller buckets, ski jump buckets) are usually constructed at the end of spillway discharge channels in order to dissipate the extra energy. Flip buckets are mainly placed at the end of chute spillways and outlets of high dams in order to dissipate the energy characterizing high-velocity flows [1]. Various models of flip buckets, such as simple, splitter, deflector, and specific compound buckets have been built, but information about the design of compound buckets is still limited and more studies are needed [2]. Rohne and Peterka [4] conducted a study on an improved flip bucket design for the US Bureau of Reclamation. The simplest flip bucket is represented by a cylindrical shell sector tangent to the floor of the flood conduit (chute or tunnel), as suggested in studies conducted in 1993 on the Grand Coulee dam located in Washington [4]. The scale effects in the hydraulic models, pressure distribution through the bucket, flow projectile, Fluids 2020, 5, 182; doi:10.3390/fluids5040182 www.mdpi.com/journal/fluids
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