Caracterização do escoamento sobre vertedouros em degraus via CFD

Abstract

À minha família, em especial à minha amada esposa, Elisângela, à minha querida filha, Caroline, que alegra nossas vidas e aos meus queridos pais, Mário e Bernadete.

Laboratory measurements and multi-block numerical simulations of the mean flow and turbulence in the non-aerated skimming flow region of steep stepped spillways

“…For this reason, local velocity data where air concentration is different from zero have been indicated with unfilled symbols whereas filled symbols refer to data where air concentration is equal to zero (see Figs. 4,5,7,9,14 and 15). Observations undertaken with tracers, along with the conductivity probe and the backflushing Pitot tube located in different verticals for each cross section, revealed an essentially two-dimensional (2D) flow above the step cavities, as expected.…”

“…A small number of simulations of the skimming flow over stepped spillways have been communicated very recently [5,23,[29][30][31]79], describing both the aerated and non-aerated flow regions. A detailed analysis of the above contributions for stepped spillways is presented in Table 1, revealing the following features/issues: (i) The comparisons between numerical and experimental results in those papers have been mostly of qualitative nature; Issues with the measurements in the aerated region [86] Cheng et al [30,31] (ii) whereas Chen et al [29] (see also Yasuda et al [86]), Cheng et al [30,31] and Arantes [5] solved the flows of water and air altogether (which was defined as Partial Volume-of-Fluid (VoF) method in Bombardelli et al [16]), Tabbara et al [79] employed a numerical strategy based on re-meshing each time step.…”

“…A small number of simulations of the skimming flow over stepped spillways have been communicated very recently [5,23,[29][30][31]79], describing both the aerated and non-aerated flow regions. A detailed analysis of the above contributions for stepped spillways is presented in Table 1, revealing the following features/issues: (i) The comparisons between numerical and experimental results in those papers have been mostly of qualitative nature; Issues with the measurements in the aerated region [86] Cheng et al [30,31] (ii) whereas Chen et al [29] (see also Yasuda et al [86]), Cheng et al [30,31] and Arantes [5] solved the flows of water and air altogether (which was defined as Partial Volume-of-Fluid (VoF) method in Bombardelli et al [16]), Tabbara et al [79] employed a numerical strategy based on re-meshing each time step. In turn, Carvalho and Amador [23] used a purported VoF method, but they did not report comparisons of numerical results with data of the location of the free surface; (iii) some of the simulations have been developed using unstructured grids with good resolution near the walls but with a lower resolution near the free surface; (iv) only the papers by Cheng et al [30,31] and Carvalho and Amador [23] include discussions on the distribution of turbulence statistics in the steps through contours of the turbulent kinetic energy (TKE) obtained numerically; (v) experimental data obtained in some papers to validate the numerical simulations corresponded to relatively small facilities with potential significant scale effects; (vi) to the best of our knowledge, very few numerical analyses of the non-aerated flow region which present and discuss comprehensive comparisons of computational results with data have been published in reputed peer-reviewed literature.…”

Simulação Numérica De Escoamentos Com Superfícies Livres Empregando O Método Weakly Compressible Smoothed Particle Hydrodynamics (Wcsph) E O Processamento Em Paralelo Com Unidades De Processamento Gráfico E a Api Cuda

“…No Brasil, conforme Arantes (2007), desde a década de 1980 são realizados estudos com modelos reduzidos de vertedouros em degraus, que objetivam verificar a ocorrência de cavitação e a configuração dos degraus que leva a uma maior perda de energia relativa. No entanto, o número de combinações geométricas e de configurações possíveis elevam consideravelmente os esforços empreendidos na execução de ensaios com tais modelos (Arantes, 2007).…”

Analysis of Two Phase Flows on Stepped Spillways

“…In addition, having a good numerical code, it may be possible to obtain the pressure distribution along the structure and to localize the potential cavitation regions, allowing to "test numerically" possible solutions to enhance the air content and to reduce proposed for the steps. In general the stepped design takes into account the higher energy dissipation efficiency of the stepped chutes, when compared with smooth chutes, because it implies in reduction of costs of the dissipation basin (Arantes, 2007). Fig.…”