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Numerical Study of Dam Spilling Water

Author(s): Javier Anez; Julien Reveillon; Benjamin Duret; Yvan Bercovitz; Francois-Xavier Demoulin; Hakim Younes Hamdani

Linked Author(s): Yvan BERCOVITZ, François-xavier Demoulin

Keywords: Jet water fall; Interface Resolution Quality (IRQ); Euler-Lagrange Spray Atomization (ELSA)

Abstract: The spillway of a dam evacuates the water from the reservoir it closes, in order to limit the rise of the water following flood events. The released water falls along the dam and causes a succession of hydraulic impacts at the foot of the dam whose force and frequency depend on the height of the fall and the atomization process during the fall. In last years, significant examples of scouring risk at the foot dams have been observed, like events at Kariba dam or Oroville dam. More generally, the accumulation of statistical data and scientific advances in hydrology gives rise to re-evaluations of the extreme flood discharges that can transit spillways. To have a better understanding of this physical process, the implementation of numerical modeling of different scenarios allows, on the one hand, to analyze the resistive capacities of the structure and, on the other hand, to propose appropriate solutions for an optimal cost. CFD (Computational Fluid Dynamic) is an ideal tool since it allows us to consider a lot of dam-related operational situations such as the type of spillways, the water elevation, etc. In these kinds of flows, jet dispersion process seems to be important on energy dissipation process. Therefore, it becomes advantageous to develop a two-phase liquid-gas model to take into account the gravitational effects. The proposed numerical approach focuses on the description of the two-phase flow, where liquid and gas are considered as two species of a unique turbulent flow. This is the case for water spilled from high dams in hydroelectric power plants. The purpose of the present study is to extend this approach for flows with high density-acceleration fluctuations in which the gravity may act either as a destabilizing or a stabilizing force on the liquid-gas interface. For the destabilizing case, the gravity contribution expresses the increase of liquid dispersion due to phenomena linked to the Raleigh-Benard or Raleigh-Taylor instabilities. The ultimate aim is to conduct numerical simulations of water spilled from hydroelectric power plants on an industrial scale. The validation test case consisted of a 9-meters high, waterfall, installed at EDF Lab Chatou, for which a comprehensive experimental database was set up. Results showed that the model with the enhanced gravity-based feature exhibited comparable results in agreement with experiments firstly before the fall of water where low-turbulent flow was encountered, and secondly after the fall of water where it effectively captured the liquid-gas surface instabilities and liquid structure detachments downward in the dispersed spray region.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022620

Year: 2022

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