Author(s): Cagri Turan; Marcela S. Politano; Pablo M. Carrica; And Larry Weber
Linked Author(s): Cagri Turan
Keywords: Water entrainment; Free surface jet; Two phase flow model
Abstract: It has been observed that strong liquid entrainment is caused by surface jets. This water entrainment has important environmental and ecological impacts on hydropower installations. Strong surface jets are created when defectors are installed in spillways, causing water entrainment from the powerhouse into the jet region with the consequent mixing of transported properties like temperature and dissolved gas concentrations. This liquid entrainment was observed in both prototype and model scales. Most of the numerical studies found in the literature predict the flow field on dams using standard single phase isotropic turbulence models. Though these models can be reasonably accurate when plunging jets impact the tailwater pool, they fail to maintain surface jets and therefore they can not predict water entrainment. In this study a two phase anisotropic turbulence model that accounts for attenuation of the normal fluctuations at the free surface is used to predict the water entrainment on Wanapum Dam, Washington State. The model takes into account the bubble-induced turbulence suppression and production. The model is implemented into the commercial CFD code FLUENT using User Defined Functions. The results demonstrate good agreement with model and prototype scale velocity data. It is observed that the proposed model is able to capture the physical process leading to water entrainment.
Year: 2007