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François Avellan

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Publications associées (218)

Numerical Simulation of Nonlinear Self Oscillations of a Full Load Vortex Rope

François Avellan, Christophe Nicolet, Nicolas Ruchonnet, Pierre Maruzewski, Vlad Hasmatuchi, Sébastien Alligné

Self excited instabilities or oscillations of a cavitating full load vortex rope occur due to an interaction between the gas volume and the acoustic waves. From the onset of the oscillations, the amplitudes grow until they reach a maximum, called the “limi ...

2009

Experimental Investigation of Flow Instabilities and Rotating Stall in a High-Energy Centrifugal Pump Stage

François Avellan, Philippe Dupont, Maher Kayal, Mohamed Farhat, Laurent Fabre, Stefan Berten

In centrifugal pumps, the interaction between the rotating impeller and the stationary diffuser generates specific pressure fluctuation patterns. When the pump is operated at off design conditions, these pressure fluctuations increase. The resulting rise o ...

ASME2009

Transient Behavior of Variable Speed Pump-Turbine Units

François Avellan, Basile Kawkabani, Alexander Schwery, Jean-Jacques Simond, Christophe Nicolet, Yves Pannatier

2008

Pumped Storage Units to Stabilize Mixed Islanded Power Network : A Transient Analysis

François Avellan, Basile Kawkabani, Jean-Jacques Simond, Philippe Allenbach

2008

One-Dimensional Analysis of Full Load Draft Tube Surge

François Avellan, Christophe Nicolet, Mohamed Farhat

One-dimensional stability analysis of a hydraulic system composed of a penstock, a runner, and a draft tube was carried out to determine the cause of the full load draft tube surge. It is assumed that the cavity volume at the runner exit is a function of t ...

2008

Numerical investigations of fluid structure coupling: oscillating hydrofoil

François Avellan, Olivier Braun, 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

Analysis of the Cavitating Draft Tube Vortex in a Francis Turbine Using Particle Image Velocimetry Measurements in Two-Phase Flow

François Avellan, Monica Iliescu

Partial flow rate operation of hydroturbines with constant pitch blades causes complex unstable cavitating flow in the diffuser cone. A particle image velocimetry (PIV) system allows investigating the flow velocity field in the case of a developing cavitat ...

2008

Hydro Elastic Behavior of Vibrating Blades

François Avellan, Mohamed Farhat, Philippe Ausoni, Olivier Braun, Cécile Münch-Alligné

Fluid-structure investigations in hydraulic machines using coupled simulations are extremely time-consuming; therefore we develop an alternative method. In this paper, a model is proposed to predict fluid-structure coupling by linearizing the hydrodynamic ...

International Association For Hydraulic Research2008

Surface Roughness Impact on Francis Turbine Performances and Prediction of Efficiency Step Up

François Avellan, Henri-Pascal Mombelli, Pierre Maruzewski, Vlad Hasmatuchi

In the process of turbine modernizations, the investigation of the influences of water passage roughness on radial flow machine performance is crucial and validates the efficiency step up between reduced scale model and prototype. This study presents the s ...

International Association For Hydraulic Research2008

Transient Behavior of variable speed pump-turbine units

François Avellan, Basile Kawkabani, Alexander Schwery, Jean-Jacques Simond, Christophe Nicolet, Yves Pannatier

This paper presents the modeling, simulation and analysis of the dynamic behavior of a fictitious 2x320 MW variable speed pump-turbine power plant including hydraulic system, electrical installations, rotating inertias and control systems. First, the model ...

International Association For Hydraulic Research2008

Axisymmetric swirling flow simulation of the draft tube vortex in Francis turbines at partial discharge

François Avellan

The flow in the draft tube cone of Francis turbines operated at partial discharge is a complex hydrodynamic phenomenon where an incoming steady axisymmetric swirling flow evolves into a three-dimensional unsteady flow field with precessing helical vortex ( ...

International Association For Hydraulic Research2008

Influence of the vortex rope location of a Francis Turbine on the hydraulic system stability

François Avellan, Basile Kawkabani, Jean-Jacques Simond, Philippe Allenbach, Christophe Nicolet, Sébastien Alligné

Hydroelectric power plants are known for their ability to cover variations of the consumption in electrical power networks. In order to follow this changing demand, hydraulic machines are subject to off-design operation. In that case, the swirling flow lea ...

International Association For Hydraulic Research2008

One-dimensional analysis of full load draft tube surge

François Avellan, Christophe Nicolet, Mohamed Farhat

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

Modeling and Numerical Simulation of a Complete Hydrolelectric Production Site

François Avellan, Jean-Jacques Simond

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

2007

Cavitation in Kármán Vortex Shedding from 2D Hydrofoil: Wall Roughness effects

François Avellan, Mohamed Farhat, Philippe Ausoni

The present study deals with the shedding process of the Kármán vortices in the wake of a NACA0009 hydrofoil at high Reynolds number. This research addresses the effects of the foil leading edge roughness on the wake dynamic with a special focus on the vor ...

2007

Turbine Speed Governor Parameters Validation in Islanded Production

François Avellan, Basile Kawkabani, Jean-Jacques Simond, Philippe Allenbach, Christophe Nicolet, Bob Greiveldinger

The transient behavior of hydroelectric power plants is of high interest for ensuring stability of islanded electrical power networks. Therefore, it is suitable to determine and validate the set of parameters of a turbine speed governor using a realistic s ...

2007

High Speed Flow Visualisation of an Impinging Jet on a Pelton Turbine Bucket

Alexandre Perrig, François Avellan, Mohamed Farhat

This paper deals with flow investigations using endoscopes in a single-injector reduced scale Pelton turbine performed with a CMOS high-speed camera. Both onboard and external visualizations techniques of the flow in a bucket are presented. The flow observ ...

ASME2007

Experimental Study and Numerical Simulation of the Flindt Draft Tube Rotating Vortex

François Avellan, Monica Iliescu

The dynamics of the rotating vortex taking place in the discharge ring of a Francis turbine for partial flow rate operating conditions and cavitation free conditions is studied by carrying out both experimental flow survey and numerical simulations. 2D las ...

2007

Cavitation Influence on Kármán Vortex Shedding and Induced Hydrofoil Vibrations

François Avellan, Mohamed Farhat, Philippe Ausoni, Eduard Egusquiza

The present study deals with the shedding process of the von Kármán vortices at the trailing edge of a 2D hydrofoil at high Reynolds number. This research focuses mainly on the effects of cavitation and fluid-structure interaction on the mechanism of the v ...

2007

Cavitation bubble behavior inside a liquid jet

François Avellan, Peter Monkewitz, Mohamed Farhat, Etienne Robert, Jacques Lettry

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

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