Lower nappe aeration in smooth channels: experimental data and numerical simulation

Arantes, Eudes José; Porto, Rodrigo Martins; Gulliver, John S.; Lima, Alberto Cardoso Martins; Schulz, Harry Edmar

doi:10.1590/s0001-37652010000200027

Cited by 10 publications

(4 citation statements)

References 8 publications

(8 reference statements)

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“…Three-dimensional flow simulations were performed using the Ansys CFX software, which uses the finite volume method (Ansys Inc., 2013) and has a history of successful use for CFD simulations of various hydraulic structures (Arantes, 2007;Arantes et al, 2010;Dettmer et al, 2013;Gabl & Righetti, 2018;Sanagiotto et al, 2019aSanagiotto et al, , 2019b.…”

Section: Numerical Modeling and Governing Equationsmentioning

confidence: 99%

Combination of experimental and numerical approaches to determine the main characteristics of skimming flow in stepped spillways

Tassinari

Sanagiotto

Marques

et al. 2020

RBRH

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The traditional approach for the hydrodynamic characterization of the flow down stepped spillways is through physical modeling, which is susceptible to scale effects and has limitations related to experimental apparatus, laboratory space and the spatial discretization of data collection. Computational fluid dynamics (CFD) is an important tool for hydrodynamic analysis because, if used properly, it presents great potential for application in hydraulics. In this work, CFD was used to model the skimming flow down a stepped spillway to investigate the effects of possible pressure measurement errors due to uncertainties in the position of the sensors within the steps. The numerical model was validated through literature velocity profiles and pressure experimental data. The results showed that the best values of water fraction (α) to define free surface are α = 0.30 in the nonaerated region and α = 0.10 in the aerated region. Statistical parameters were calculated using experimental data to estimate extreme pressures. These parameters and the simulation results were used to determine that the extreme maximum and minimum pressures occur, respectively, in the region of 0.81 < x/l < 0.98, in the horizontal faces, and in the region of 0.93 < y/h < 0.98, in the vertical faces.

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Section: Numerical Modeling and Governing Equationsmentioning

confidence: 99%

Combination of experimental and numerical approaches to determine the main characteristics of skimming flow in stepped spillways

Tassinari

Sanagiotto

Marques

et al. 2020

RBRH

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“…See, for example, Chanson (1994). The air concentration distribution, downstream of the inception point, may be obtained, for example, using a diffusion model (Arantes et al, 2010), as proposed by Chanson (2000), which leads to Eq. 4.…”

Section: Self-aerated Flowmentioning

confidence: 99%

Analysis of Two Phase Flows on Stepped Spillways

Lobosco¹,

Schulz²,

Simões³

2011

Hydrodynamics - Optimizing Methods and Tools

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cavitation damages (Gomes, 2006;Olinger, 2001). The obtained results presented in this chapter are still approximate, but already show that the problem is treatable using numerical tools. The main problems, as shown in this chapter, are related to the behavior of the free surface. This study considers the skimmimg flow regime, which generally occurs for large specific water discharges (Chanson, 2000). It is expected that the bed profile of the inlet structure affects the position of the inception point of the aeration (Boes & Hager, 2003a;Chanson, 2001). This study presents results of computational analyses for two inlet conditions of a stepped chute with an ogee crest. The aeration of the flows was investigated for an entry profile containing 1) steps with the same size, and 2)"transition steps" (steps with sizes increasing between the smooth bed and the stepped bed). In the last few decades, the computational fluid dynamics, CFD, has imposed itself as one of the best tools for the prediction of flow fields with accuracy and detail (Versteeg & Malalasekera, 1995). But even considering its success, complex flows still need many efforts to be completely understood. The description of the physical processes of a two phase flow involves a broad variety of computational methodologies to predict the quantities of the constituent components and the behavior of the interface. In the present study, the numerical procedures for the stepped channel flow simulations were conducted using the open softwares Salome and OpenFoam® (Open Source Field Operation and Manipulation), for mesh generation and CFD, respectively. In a general way, it may be commented that the implementation of CFD modeling is still limited, due, in part, to the relatively high costs of the commercial softwares. OpenFoam® is an open CFD software that helps to fill this gap. For the purposes of this chapter, the particularly relevant characteristic of the mentioned software is its ability to simulate flows interacting with hydraulic structures. The skimming flows along stepped chutes are inherently turbulent (Lima, 2003, Chamani, 2000, and their "turbulent characteristics" were investigated here using the "k-ε" model of turbulence, and adequate wall functions for the wall boundaries. The VOF method (Volume Of Fluid), was used for the interface-capturing procedures in the two-fluid model. Further, the PISO method (Pressure-Implicit with Splitting of Operators) was used as the pressurevelocity coupling scheme. In the calculations performed for this chapter, the rasInterFoam solver was chosen because, traditionally, the flow along spillways is considered incompressible (its velocity is much lower than the speed of the sound in water). The main purposes of this chapter were to show the implementation of the mentioned open softwares for the problem of aerated flows over stepped chutes, and to compare some calculated hydrodynamics characteristics with the literature, like the pressure distribution on the steps. The literature addresses the position of the incept...

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“…No caso da aeração induzida, vários trabalhos foram desenvolvidos visando a modelagem matemática do fenômeno. Considerando procedimentos numéricos,Arantes et al (2010) compararam dados experimentais disponíveis na literatura com resultados de simulações de mecânica de fluidos computacional (CFD) tendo verificado uma correlação bastante adequada entre a experiência e a simulação. Entretanto, os autores frisam que a ordem de grandeza da absorção de ar foi atingida, porém os resultados não reproduzem os detalhes da absorção, sendo necessário efetuar mais estudos.…”

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“…No Brasil, com o advento da construção de grandes aproveitamentos hidroelétricos entre as décadas de 1970 e 1980, muitos estudos em aeração em vertedores foram desenvolvidos. Destacam-se novamente aqui as primeiras conclusões apresentadas por Pinto,Neidert e Otta (1982), acrescentando-se outros autores nacionais comoBorsari (1986), Serra (1986,Carvalho (1997),Lima (2003),Moraes (2007),Lima, Schulz e Gulliver (2008) eArantes et al (2010), que evoluiram nos estudos para a otimização destes dispositivos.…”

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Análise da aeração em escoamentos de altas velocidades em calhas de vertedores

Brito¹

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Fazer da escola a base para o Povo tomar o poder." Samora Machel "Deus quer, o Homem pensa e a Obra nasce." Fernando Pessoa "As ciências não tentam explicar; dificilmente tentam sequer interpretar; elas fazem modelos, principalmente. Por modelo entenda-se uma construção matemática que, com o acréscimo de certas informações verbais, descreve fenômenos observados." Von Neumann i AGRADECIMENTOS Em primeiro lugar a Deus, pela minha vida e oportunidade de realizar este mestrado. Ao meu orientador Harry Edmar Schulz pela orientação científica, a dedicação, amizade, apoio e empenho incansáveis em todo o trabalho realizado. À todos professores do programa de Pós-Graduação em Engenharia Hidráulica e Saneamento, pelos conhecimentos adquiridos ao longo do curso. Ao colega e amigo André Simões pela colaboração incansável prestada na realização deste trabalho. Aos colegas do Laboratório de Fenômenos de Transporte e do mestrado especialmente Júlio Cesar, Daniel, Tiago, Raquel e Guilherme pelo companheirismo e amizade que nos norteou ao longo destes anos. À todos funcionários do Departamento especialmente a Pavi, Sá, Rose e Marília por toda gentileza e amabilidade prestada ao longo destes dois anos. Ao Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) e ao Ministério de Ciência e Tecnologia de Moçambique pela bolsa de estudo concedida. Ao Instituto Superior Politécnico de Tete pela licença concedida para realizar este treinamento de mestrado. Ao pessoal da república albergue por toda amizade e acolhimento. À minha esposa Haúa e filhos Gisela, António e Ashraf, aos quais espero retribuir o tempo dedicado a este trabalho. À meus irmãos pelo apoio moral.

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Lower nappe aeration in smooth channels: experimental data and numerical simulation

Cited by 10 publications

References 8 publications

Combination of experimental and numerical approaches to determine the main characteristics of skimming flow in stepped spillways

Combination of experimental and numerical approaches to determine the main characteristics of skimming flow in stepped spillways

Analysis of Two Phase Flows on Stepped Spillways

Análise da aeração em escoamentos de altas velocidades em calhas de vertedores

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