Publications by François Avellan

Upper part-load instability in a reduced-scale Francis turbine: an experimental study

François Avellan, Andres Müller, Elena Vagnoni, Ali Amini

Francis turbines with medium or high specific speeds may experience a particular type of instability in the upper part load in which the precessing vortex has an elliptical shape. The occurrence of the upper part-load instability (UPLI) is accompanied by l ...

SPRINGER2023

CFD simulations of hydraulic short-circuits in junctions, application to the Grand’Maison power plant

François Avellan, Cécile Münch-Alligné

In the framework of the XFLEX HYDRO H2020 European Project, the pumped-storage power plant of Grand'Maison (France), owned by Electricité De France, focuses on the implementation of the hydraulic short-circuit (HSC) operating mode. This mode increases the ...

2022

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

Numerical simulations of Pelton turbine flow to predict large head variation influence

François Avellan, Steve Crettenand, Cécile Münch-Alligné, Siamak Alimirzazadeh

In the framework of the new feed-in-tariff system in Switzerland for Small Hydropower Plants (SHP), the aim of the SmallFLEX project, led by HES-SO Valais and performed in collaboration with EPFL, WSL, EAWAG, PVE, and FMV, is to show how SHP can provide wi ...

IOP PUBLISHING LTD2021

Vortex impingement onto an axisymmetric obstacle - subcritical bifurcation to vortex breakdown

François Avellan, François Gallaire

A swirling wake flow submitted to an adverse pressure gradient is studied by bifurcation analysis, modal analysis and direct numerical simulations. In contrast to experiments in diverging tubes, the adverse pressure gradient is imposed by the presence of a ...

Cambridge University Press2021

Swiss Potential for Hydropower Generation and Storage - Synthesis report

François Avellan, Pedro Filipe De Almeida Manso, Paolo Burlando, David Felix, Martin Schmid

Hydropower (HP) is the backbone of the Swiss electricity system providing around 60 % (36 TWh/a) of the total electricity generated on a yearly average. With the planned phase-out of nuclear power plants, HP and other Renewable Energy Sources (RES) will ne ...

ETH Zurich2021

How to teach neural networks to mesh: Application on 2-D simplicial contours

François Avellan, Pascal Clausen, Alexis Papagiannopoulos

A machine learning meshing scheme for the generation of 2-D simplicial meshes is proposed based on the predictions of neural networks. The data extracted from meshed contours are utilized to train neural networks which are used to approximate the number of ...

2021

Understanding the coherent structures for different fluctuation frequencies at partial load condition of a Francis turbine

François Avellan

More and more hydropower plants are operating as regulator of renewable energy such as solar and wind energy resources. Because these renewable energy resources are highly volatile, so hydraulic turbines have to switch working condition in a wide flow rang ...

IOP PUBLISHING LTD2021

An experimental study on the upper part-load elliptical vortex instability in a Francis turbine

François Avellan, Andres Müller, Arthur Tristan Favrel, Elena Vagnoni, Ali Amini

This paper presents preliminary results of an experimental study on the occurrence and development of the upper part-load instability in a reduced-scale Francis turbine. The study includes draft tube pressure measurements, high-speed flow visualization, an ...

IOP PUBLISHING LTD2021

Turbine mode start-up simulation of a FSFC variable speed pump-turbine prototype - Part I: 1D simulation

François Avellan, Antoine Béguin, Sébastien Alligné, Drazen Dujic

Variable speed hydroelectric units equipped with full size frequency converter (FSFC) offer high operational flexibility enabling fast operating point transitions which increase grid regulation capacities. The XFLEX HYDRO H2020 European research project ai ...

IOP PUBLISHING LTD2021

CFD simulations of a Y-junction for the implementation of hydraulic short-circuit operating mode

François Avellan, Cécile Münch-Alligné, Daniel Biner

In the framework of the XFLEX HYDRO H2020 European Project, one of the demonstrators focuses on the implementation of the hydraulic short-circuit on the pump storage power plant of Grand-Maison owned by Electricite De France (EDF). The Grand-Maison power p ...

IOP PUBLISHING LTD2021

Investigation of the Time Resolution Set Up Used to Compute the Full Load Vortex Rope in a Francis Turbine

François Avellan, Andres Müller, Cécile Münch-Alligné, Arthur Tristan Favrel

The flow in a Francis turbine at full load is characterised by the development of an axial vortex rope in the draft tube. The vortex rope often promotes cavitation if the turbine is operated at a sufficiently low Thoma number. Furthermore, the vortex rope ...

2021

Application of particle-based numerical analysis to the practical design of Pelton turbine

François Avellan, Siamak Alimirzazadeh, Takashi Kumashiro

For the design optimization of the Pelton turbine, it is highly demanded to investigate the flow inside the turbine casing, which includes the water jet from the nozzles, the interaction between the jet and rotating runner, and the flow ejected from the bu ...

IOP PUBLISHING LTD2021

DuoTurbo: Implementation of a Counter-Rotating Hydroturbine for Energy Recovery in Drinking Water Networks

François Avellan, Samuel Chevailler, Cécile Münch-Alligné, Vlad Hasmatuchi, Daniel Biner

To enhance the sustainability of water supply systems, the development of new technologies for micro scale hydropower remains an active field of research. The present paper deals with the implementation of a new micro-hydroelectric system for drinking wate ...

2021

Turbine mode start-up simulation of a variable speed Francis pump-turbine prototype - Part II: 3-D unsteady CFD and FEM

François Avellan, Drazen Dujic

The Z'Mutt pumping station, part of the Grande Dixence hydroelectric scheme, is one of the demonstrators of the XFLEX HYDRO project. A 5 MW reversible pump-turbine prototype equipped with a full-size frequency converter (FSFC) is used to investigate dynami ...

IOP PUBLISHING LTD2021

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

Computational parametric analysis of the design of cross-flow turbines under constraints

François Avellan, Sebastián Camilo Leguizamón Sarmiento

The cross-flow turbine is an attractive technology for small-scale hydropower generation thanks to its low capital cost and relatively high efficiency even under partial discharge operating conditions. It has been proposed that this kind of turbine can be ...

Pergamon-Elsevier Science Ltd2020

Evaluation of a Dynamic Transfer Matrix for a Hydraulic Turbine

François Avellan, Andres Müller, Keita Yamamoto

It is well known that hydraulic machines experience various types of flow instabilities causing a negative influence on the system under off-design operations. The transfer matrix method correlating the flow properties in upstream and downstream of hydraul ...

2020

GPU-accelerated numerical analysis of jet interference in a six-jet Pelton turbine using Finite Volume Particle Method

François Avellan, Christian Vessaz, Ebrahim Jahanbakhsh, Sebastián Camilo Leguizamón Sarmiento, Siamak Alimirzazadeh, Audrey Paulette Solange Maertens, Takashi Kumashiro

The Pelton turbine is an impulse turbine typically installed for high head hydroelectric power plants. For a site with a rated head H and discharge Q, a higher specific speed turbine results in a more compact generating unit with reduced manufacturing cost ...

Pergamon-Elsevier Science Ltd2020

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