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François Avellan

Cette personne a quitté l’EPFL

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Publications associées (218)

Page 7 sur 11

Hydroacoustic Modeling of Rotor Stator Interaction in Francis Pump-Turbine

François Avellan, Christophe Nicolet, Nicolas Ruchonnet

A one-dimensional hydroacoustic model is set up to perform the numerical simulation of the rotor-stator interaction of a Francis pump-turbine scaled model. The numerical results enable to identify both rotating diametrical modes in the vaneless gap between ...

2006

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

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

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

One-dimensional analysis of full load draft tube surge

François Avellan, Mohamed Farhat, Christophe Nicolet

A previous report by the present authors [1] clarified the diffuser effect of the draft tube and the effects of swirl in the runner downstream on the hydraulic instabilities in power generation plants. The present study was intended to study the effect of ...

International Association For Hydraulic Research2008

Numerical investigation of the jet velocity profile and its influence on the Pelton turbine performance

François Avellan, Ebrahim Jahanbakhsh, Audrey Paulette Solange Maertens, Sebastián Camilo Leguizamón Sarmiento, Siamak Alimirzazadeh

Numerical investigation of the unsteady flow patterns around the bucket can be helpful to improve the Pelton turbine efficiency. In fact, by studying the loss mechanisms in the flow, one can optimize the bucket design. For this purpose, an accurate investi ...

IOP Publishing2019

Numerical investigations of fluid structure coupling: oscillating hydrofoil

François Avellan, Cécile Münch-Alligné

This paper presents an investigation of the hydro elastic behavior of vibrating blades in hydraulic machines, which is of strong interest for turbo machinery applications. As a representative case study for vibrating blade in hydraulic machines, a NACA 000 ...

2008

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

Cavitation bubble behavior inside a liquid jet

François Avellan, Mohamed Farhat, Peter Monkewitz, Etienne Robert

The growth and collapse of laser-induced vapor cavities inside axisymmetric free-falling liquid water jets have been studied. Bubbles of different size are generated at various distances from the jet axis and the effects on the jet interface are recorded b ...

2007

Modal behavior of a reduced scale pump turbine impeller. Part II: Numerical simulation

François Avellan, Mohamed Farhat, Xiaopeng Huang

A numerical simulation has been carried out to analyze the modal behavior of a reduced scale pump-turbine impeller. The simulation has been done using FEM method, in air and in water. The same boundary conditions than in the experiment were considered: fre ...

International Association For Hydraulic Research2010

Influence of the Pump-Turbine Guide Vanes Vibrations on the Pressure Fluctuations in the Rotor-Stator Vaneless Gap

François Avellan, Mohamed Farhat, Vlad Hasmatuchi, Steven Roth

We investigate the Rotor-Stator Interaction in a pump-turbine reduced scale model by considering fluid-structure coupling. The pressure fluctuations amplitude in the rotor-stator vaneless gap has generally been shown to increase linearly with the operating ...

2011

On the Hydroelectric Stability of an Islanded Power Network

François Avellan, Jean-Jacques Simond, Philippe Allenbach

slanded power networks comprising a small number of large power plants are subject to perturbations leading to important transients, and, hence need high performance governors. The design of these governors requires a detailed model of the system. This is ...

2006

Numerical Analysis of Flow Phenomena Related to the Unstable Energy-Discharge Characteristic of a Pump-Turbine in Pump Mode

François Avellan

Regions of positive slope in the pressure-discharge characteristics are one of the major concerns in design and operation of centrifugal pumps, as they are limiting the admissible operating range to values above the critical discharge. The industrial pump ...

2005

Simulation tool linking hydroelectric production sites and electrical networks

François Avellan, Jean-Jacques Simond, Christophe Nicolet, Philippe Allenbach

Since many years the EPFL Laboratory of Electrical Machines develops SIMSEN, a numerical software package for the simulation of electrical power systems and adjustable speed drives, in transient and steady-state conditions, having an arbitrary topology. SI ...

2006

Dynamical behaviour comparison between variable speed and synchronous machines with PSS

François Avellan, Jean-Jacques Simond, Basile Kawkabani, Alexander Schwery

2010

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

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

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

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 Publishing2021

Dynamics and Intensity of Erosive Partial Cavitation

François Avellan, Mohamed Farhat

An experimental work has been carried out to investigate the dynamic behavior and the intensity of erosive partial cavitation on a 2-D hydrofoil. Both sheet (stable) and cloud (unstable) cavitation have been tested in a cavitation tunnel for various free s ...

2007

Part Load Vortex Rope as a Global Unstable Mode

François Avellan, François Gallaire, Simon Pasche

Renewable energy sources (RES) have reached 23.7% of the worldwide electrical generation production in 2015. The hydraulic energy contribution amounts to 16.6% and comes mainly form large-scale hydropower plants, where Francis turbines represents 60% of th ...

American Society of Mechanical Engineers2017

The Effects of a Tripped Turbulent Boundary Layer on Vortex Shedding from a Blunt Trailing Edge Hydrofoil

François Avellan, Mohamed Farhat, Amirreza Zobeiri

Experiments on vortex shedding from a blunt trailing edge symmetric hydrofoil operating at zero angle of attack in a uniform high speed flow, Re-h = 16.1 . 10(3) - 96.6 . 10(3), where the reference length h is the trailing edge thickness, are reported. The ...

2012

On the physical mechanisms governing self-excited pressure surge in Francis turbines

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Keita Yamamoto

The required operating range for hydraulic machines is continually extended in an effort to integrate renewable energy sources with unsteady power outputs into the existing electrical grid. The off-design operation however brings forth unfavorable flow pat ...

IOP Publishing2014

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

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

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