Author(s): Marcela Politano; Antonio Arenas Amado; Jesse Naymik; Kelvin Andersonv; Ralph Myersv; Larry Weber; Company; Oise
Linked Author(s): Marcela Politano, Larry J. Weber
Keywords: Temperature; Reservoir; Stratification; CFD; Thermal Model
Abstract: hydropower facilities can change water temperature, which impacts natural habitat and survival of migrating fish. This paper presents the development of a Computational Fluid Dynamics (CFD) model capable of simulating the hydrodynamics and temperature dynamics in Brownlee Reservoir and turbine intakes. The purpose of the model is to assist in the evaluation of possible mitigation measures to alleviate high temperatures downstream of the dam. Numerical modeling of the thermal dynamics in Brownlee Reservoir poses significant challenges due to the strong Rayleigh number of a deep reservoir with large temperature gradients. Important currents due to natural convection affect momentum, turbulence, and the resulting temperature distribution in the reservoir. In this study, an unsteady three dimensional non hydrostatic model was developed. The model is based on the Reynolds Averaged Navier Stokes equations, using a Boussinesq approach. A realizable k ε− model is used for turbulence closure. The model takes into account heat exchanges between the reservoir and atmosphere. The model was validated against field data collected in 1999 and 2002. The effectiveness of alteringturbine operations to reduce downstream temperature wasevaluated. Numerical results indicate that controlling turbine operations cannot effectively reduce downstream temperature to water quality standards. A hypolimnetic pump system to draw and transport cold water from the deepest region of the reservoir to the intake channel was then proposed and evaluated. According to the model, the system draws cold water without disturbing the thermocline and significantly reduces downstream temperature during low flow conditions. At high flows, the system is less efficient; however, it is still able to decrease the temperature for the majority of the time period.
Year: 2013