Publications de François Avellan

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

François Avellan, Elena Vagnoni, Andres Müller, 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, 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

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

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

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, Martin Schmid, Paolo Burlando, David Felix

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, Elena Vagnoni, Arthur Tristan Favrel, Andres Müller, 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, Drazen Dujic, Sébastien Alligné, Antoine Béguin

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