Publications by Joao Gomes Pereira Junior

Behavior of CFRP composites and epoxy adhesives after long-term exposure to outdoor and laboratory-controlled environments

Anastasios Vassilopoulos, Joao Gomes Pereira Junior

Carbon fiber reinforced polymer (CFRP) composites have shown desirable properties in aerospace, automotive, and construction industries. Focusing on the latter and in the context of strengthening existing structures, CFRP composites are typically bonded to ...

Elsevier BV2024

Prediction of unstable full load conditions in a Francis turbine prototype

François Avellan, Joao Gomes Pereira Junior, Elena Vagnoni

Francis turbines operating in full load conditions feature an axisymmetric vortex rotating in the opposite direction of the turbine runner. In low-pressure conditions, the resulting cavitation vortex may enter in an unstable self-exciting process, leading ...

ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD2022

Transposition of the mechanical behavior from model to prototype of Francis turbines

François Avellan, Eduard Egusquiza, Joao Gomes Pereira Junior

Hydropower is nowadays essential for balancing the electrical grid providing flexibility and fast response. The role of hydraulic turbines has changed from working at their Best Efficiency Point (BEP) to work in the whole operating range when demanded. Fra ...

Pergamon-Elsevier Science Ltd2020

Swirl number based transposition of flow-induced mechanical stresses from reduced scale to full-size Francis turbine runners

François Avellan, Christian Landry, Joao Gomes Pereira Junior, Arthur Tristan Favrel, Keita Yamamoto

At part load conditions, Francis turbines are subject to the emergence of a hydrodynamic instability in their draft tube, referred to as precessing vortex rope. It induces pressure pulsations in the water passages at the precession frequency of the vortex, ...

2020

Prediction of hydro-acoustic resonances in hydropower plants by a new approach based on the concept of swirl number

François Avellan, Christophe Nicolet, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior, Arthur Tristan Favrel, Loïc Andolfatto

Hydropower plant units operating in off-design conditions are subject to cavitation flow instabilities, potentially inducing hydro-acoustic resonances under certain conditions. They can be predicted by using one-dimensional numerical models of hydropower p ...

Taylor & Francis Ltd2019

Reduced scale model testing for prediction of eigenfrequencies and hydro-acoustic resonances in hydropower plants operating in off-design conditions

François Avellan, Christophe Nicolet, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior, Arthur Tristan Favrel

The massive penetration of the electrical network by renewable energy sources, such as wind and solar, pushes the operators to extend hydropower plant units operating range to meet the transmission system operator requirements. However, in off-design opera ...

2019

Dynamic modal analysis during reduced scale model tests of hydraulic turbines for hydro-acoustic characterization of cavitation flows

François Avellan, Christian Landry, Joao Gomes Pereira Junior, Arthur Tristan Favrel

Francis turbines operating at off-design conditions experience the development of unfavourable cavitation flows in the draft tube at the runner outlet, which induce pressure pulsations and hydro-acoustic resonances in the worst cases. The assessment of hyd ...

2019

Predicting the dynamic behavior of Francis turbine generating units

Joao Gomes Pereira Junior

To reduce CO2 emissions and tackle global warming, an increasing amount of electrical power consumed around the world must be obtained from renewable sources. Among these sources, hydropower has not only the advantage of leaving a very small carbon footpri ...

EPFL2019

Measurements of Cavitation Compliance in the Draft Tube Cone of a Reduced Scale Francis Turbine Operating at Part Load

François Avellan, Christophe Nicolet, Christian Landry, Joao Gomes Pereira Junior, Arthur Tristan Favrel

Francis turbines operating at part load conditions typically experience a cavitation vortex rope immediately at the runner outlet. As the compliance of this cavitation flow is much higher than the one in cavitation-free conditions, a decrease in the value ...

2018

New insight in Francis turbine cavitation vortex rope: role of the runner outlet flow swirl number

François Avellan, Christophe Nicolet, Andres Müller, Christian Landry, Joao Gomes Pereira Junior, Arthur Tristan Favrel

At part load operation, Francis turbines experience the development of a cavitation vortex rope in the draft tube, whose precession acts as a pressure excitation source. In case of resonance, the resulting pressure pulsations lead to unacceptable torque an ...

Taylor & Francis Ltd2018

Monitoring a Francis Turbine Operating Conditions

François Avellan, Joao Gomes Pereira Junior, Loïc Andolfatto

Francis turbines are designed for a specific set of operating conditions that is particular to each hydropower plant site. It allows this type of turbine to extract as much hydraulic power as possible, as long as they are operating in the right conditions. ...

2018

Renovation of hydraulic power plant: how to select the best technical options?

François Avellan, Christophe Nicolet, Christian Landry, Joao Gomes Pereira Junior, Loïc Andolfatto

With the Energy Strategy 2050, Switzerland wishes to focus on balanced utilization of hydropower potentials and new renewable energy sources to cope with nuclear energy phasing out. Integration of large amounts of new renewable energies such as wind and so ...

2018

Prediction of Francis Turbine Prototype Part Load Pressure and Output Power Fluctuations with Hydroelectric Model

François Avellan, Christophe Nicolet, Antoine Béguin, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior

The prediction of pressure and output power fluctuations amplitudes on Francis turbine prototype is a challenge for hydro-equipment industry since it is subjected to guarantees to ensure smooth and reliable operation of the hydro units. The European FP7 re ...

2017

Dynamics of the precessing vortex rope and its interaction with the system at Francis turbines part load operating conditions

François Avellan, Andres Müller, Christian Landry, Joao Gomes Pereira Junior, Arthur Tristan Favrel, Keita Yamamoto

At part load conditions, Francis turbines experience the formation of a cavitation vortex rope at the runner outlet whose precession acts as a pressure excitation source for the hydraulic circuit. This can lead to hydro-acoustic resonances characterized by ...

2017

Transposition of Francis turbine cavitation compliance at partial load to different operating conditions

François Avellan, Christian Landry, Joao Gomes Pereira Junior, Arthur Tristan Favrel

Francis turbines operating in part load conditions experience a swirling flow at the runner outlet leading to the development of a precessing cavitation vortex rope in the draft tube. This cavitation vortex rope changes drastically the velocity of pressure ...

2017

Hydroelectric System Response to Part Load Vortex Rope Excitation

François Avellan, Christophe Nicolet, Antoine Béguin, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior

The prediction of pressure and output power fluctuations amplitudes on Francis turbine prototype is a challenge for hydro-equipment industry since it is subjected to guarantees to ensure smooth and reliable operation of the hydro units. The European FP7 re ...

International Association For Hydraulic Research2016

Design and Performance Assessment of a Tidal Ducted Turbine

François Avellan, Marcel Vonlanthen, Cécile Münch-Alligné, Joao Gomes Pereira Junior

Tidal Current Energy can be eligible as one of the most interesting renewable and clean energy resources with the promise of a regular and predictable production of electricity. In the framework of the "MWATFORCE" Project from GUINARD Energies, a ducted ti ...

2009