Banca de DEFESA: LUDMILA MOURA MOREIRA MENDES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : LUDMILA MOURA MOREIRA MENDES
DATE: 10/02/2023
TIME: 09:00
LOCAL: https://conferenciaweb.rnp.br/webconf/hersilia-de-andrade-e-santos
TITLE:

Downstream hydrodynamic flow of hydroelectric plants model: assessing impacts on ichthyofauna

KEY WORDS:

Free surface flow, upstream migration, tropical rivers, numerical model

PAGES: 120
BIG AREA: Engenharias
AREA: Engenharia Civil
SUBÁREA: Engenharia Hidráulica
SPECIALTY: Hidráulica
SUMMARY:

The Hydroelectric Power Plants (HPP) are renewable energy sources whose worldwide capacity is expected to increase in the coming years. However, despite their attractive aspects to public managers, their presence fragments rivers and alters the natural flow regime, and such abiotic changes cause significant alterations in the behavior of fish species, which can become extinct depending on the degree of impact. On the other hand, in an attempt to propose sustainable solutions to existing HPP, the Ecohydraulics area tries to diagnose these impacts by using numerical modeling of the hydraulic flow and real-time fish behavior monitoring techniques. However, the development of numerical models for long stretches of rivers is not trivial, especially considering the sufficient resolution to capture small-scale physical processes, such as those proportional to fish movement, or even complex parts of the flow, such as those that occur in lateral zones of secondary flow (meanders) or in areas of turbine outflow. Therefore, the general objective of the present research was to develop numerical models of hydraulic flows downstream of dams that represent significantly the physical processes, necessary to understand the behavior of fish species, mainly related to the attraction exerted by turbines and the use of swimming corridors. In order to evaluate the use of hydrodynamic models for impacts related to HPP and ichthyofauna, a systematic review was carried out to support more holistic definitions on the subject as well as to provide information regarding the characteristics of the models to be employed. Two and three-dimensional hydrodynamic models of the hydraulic flow downstream of the Três Marias HPP (Brazil) were built and validated. Different approximations related to turbulence were applied and the hydrodynamic results will be confronted with information on the swimming capacity of Neotropical fish. After the simulation, information about hydraulic characteristics related to velocity, turbulent kinetic energy (TKE) and total hydraulic strain (THS) were obtained. This work answered the following questions: 1) Do changes occur in the velocity and turbulence fields of the flow downstream of the HPP due to its operation that may influence the behavior of fish shoals in these areas? 2) Are there swimming corridors in areas downstream of HPP that may lead fish to areas close to the turbines? 3) Where are the main studies of hydrodynamic models applied to fish population problems arising from HPP operation? 4) What are the main impacts addressed in these studies with hydrodynamic models? 5) What are the selection criteria for the studied species and techniques to obtain fish behavior data? 6) What are the main characteristics of numerical hydraulic models for impact studies on ichthyofauna due to HPP? 7) Are the three-dimensional models RANS (Reynolds Averaged Navier Stokes) and DDES (Delayed Detached Eddy Simulation) similar in the process of capturing hydraulic phenomena, important for understanding the environmental behavior of fish species, in different areas of flow along the river stretch? 8) How do the hydraulic variables magnitude velocity, turbulence and the total hydraulic strain (pointed out as important explainers of fish behavior) behave in downstream stretches of HPP over distance? The following points were observed as main results: 1) the flow fields of the HPP forebay show a higher total hydraulic strain and velocity homogeneity than the flow field of the downstream river stretch; 2) forebay velocities are low for mature individuals of all species studied, which can swim from the downstream river reach to unsafe areas in the forebay in the sustainable mode and extended by corridors available for the different flows simulated; 3) there is a broad contribution of CFD models in studies of dam impacts on fish communities, but there is a prevalence of research on fish passages; 4) an increase in research on non-salmonid, native or endangered species has been observed, especially in China; 5) the sampling of fish data, the extent of the domain and the complexity of the phenomena studied in the flow play an important role in the definition of the numerical model; 6) the selection of software is related to the type of impact studied and the association of different models has improved the simulation of fish behavior in the hydrodynamic field; 7) there is little research in the southern hemisphere and in areas with high fish diversity; 8) habitat quality and fish movement modeling are promising areas for the use of CFD; 9) differences in flow velocity, turbulent kinetic energy, and total hydraulic strain were observed for the DDES and RANS models; 10) the DDES model showed better agreement with ADCP data; 11) flow velocity was significantly related to distance from the dam, and some areas in the three-kilometer stretch may act as velocity barriers for Pimelodus maculatus. It is hoped that the contributions made by this thesis will advance the scientific discussion on environmental impacts from HPP in aquatic environments.

COMMITTEE MEMBERS:
Presidente - HERSILIA DE ANDRADE E SANTOS
Interno - LINEKER MAX GOULART COELHO
Externa à Instituição - EDNA MARIA DE FARIA VIANA - UFMG
Externo à Instituição - LUIZ GUSTAVO MARTINS DA SILVA - UFSJ