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Analysis of Factors Affecting Cavitation of Ogee Crested Spillway in Concrete Dams

Amiri Shiraz, Mohammad Reza | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55182 (09)
  4. University: Sharif University of Technolog
  5. Department: Civil Engineering
  6. Advisor(s): Khaloo, Alireza
  7. Abstract:
  8. In this study, the factors affecting cavitation in the crest of an ogee spillway were investigated. One of the factors affecting the occurrence of cavitation on the ogee crest is the ratio of the head to the design head. As the head ratio increases, the probability of cavitation on the crest increases. The value of the head is also an effective parameter for the occurrence of cavitation. The spillway crest curve is also one of the factors affecting the occurrence of cavitation on the ogee-crested spillways. In this study, the ogee crested spillway that consists of three circular arcs upstream has been investigated. 5 different head ratios have been used. For this study, OpenFOAM software, which is an open source software for computational fluid dynamics, was used to simulate the flow over the spillway at head ratios higher than the design head. Governing equations are solved numerically using the interFoam solver in OpenFOAM. The interFoam solver is used for incompressible, isothermal immiscible fluids using the fluid volume (VOF) approach. In the VOF method, the tracking of the interface between the phases is done by solving a continuity equation for the volume fraction of the phases. The phase fraction can be any value between 0 and 1. In this study, RANS turbulence models have been used to model the flow over the spillway. The structured hexagonal mesh was applied in the flow domain over the spillway in the model geometry using Ansys ICEM software. In this study, k-ε, realizable k-ε, k-ω SST and RNG k-ε turbulence models have been used. After flow modeling and verifying the results of the turbulence models with the experimental paper, the numerical model data were used to investigate the occurrence of cavitation on the ogee spillway crest. The results of the models show a linear relationship between the dimensionless ratio of the minimum bottom pressure to the head with the ratio of head to design head. The results show that, in what ratio of the flow head to the design head and how much flow head, incipient cavitation occurs on the ogee crest. The results show a non-linear relationship between the head and the proportion of head to design head. Also, the results showed that in a particular design head, with the increase of the head over the ogee crest, the incipient cavitation occurs at the lower ratio of head to design head
  9. Keywords:
  10. Cavitation ; Ogee Spillway ; OpenFOAM Software ; Reynolds Average Navier-Stocks (RANS)Method ; Volume of Fluid ; Head Ratios Higher Than the Design Head ; InterFoam Software

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