Publications de 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, Elena Vagnoni, Joao Gomes Pereira Junior

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, Joao Gomes Pereira Junior, Eduard Egusquiza

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, Arthur Tristan Favrel, Keita Yamamoto, Joao Gomes Pereira Junior

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, Arthur Tristan Favrel, Christian Landry, Sébastien Alligné, Loïc Andolfatto, Joao Gomes Pereira Junior

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, Arthur Tristan Favrel, Joao Gomes Pereira Junior, Christian Landry, Sébastien Alligné

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

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

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

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