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François Avellan

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Related publications (218)

Page 3 of 11

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

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

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

Hill chart modelling using the Hermite polynomial chaos expansion for the performance prediction of pumps running as turbines

François Avellan, Loïc Andolfatto, João Nuno Gomes Borga Delgado

Pumps running as turbines are suitable hydraulic machines for micro hydropower applications. The selection of the proper pumps to install in a given site still remains a major challenge, as pump manufacturers do not provide the characteristic curves data i ...

Elsevier2019

Experimental investigation of added mass effects on a Francis turbine runner in still water

François Avellan

The mechanical design of hydraulic turbines is conditioned by the dynamic response of the runner that is usually estimated by a computational model. Nevertheless, the runner has complex boundary conditions that are difficult to include in the computational ...

2006

Mathematical modelling of swirling flow in hydraulic turbines for the full operating range

François Avellan

We introduce and validate a novel mathematical model for computing the radial profiles of both axial and circumferential velocity components, respectively, of the swirling flow exiting the runner of hydraulic turbines within the full operating range. We as ...

Elsevier2011

Kármán vortex shedding in the wake of a 2D hydrofoil: Measurement and numerical simulation

François Avellan, Mohamed Farhat, Youcef Ait Bouziad

The present study deals with the shedding process of the Kármán vortices at the trailing edge of a 2D hydrofoil at high Reynolds numbers. Investigations are performed in order to evaluate the ability of an unsteady numerical simulation to accurately reprod ...

2006

Numerical simulation of fluid added mass effect on a francis turbine runner

François Avellan, Mohamed Farhat

In this paper, a numerical simulation to analyze the influence of the surrounding water in a turbine runner has been carried out using finite element method (FEM). First, the sensitivity of the FEM model on the element shape and mesh density has been analy ...

2007

Rotor-Stator Interaction Induced Pressure Fluctuations: CFD and Hydroacoustic Simulations in the Stationary Components of a Multistage Centrifugal Pump

François Avellan, Mohamed Farhat, Philippe Dupont

In a centrifugal pump the interaction between the rotating impeller pressure field and the stationary diffuser pressure field yields pressure fluctuations as the result of a modulation process. These fluctuations may induce hydroacoustic pressure fluctuati ...

2007

High-speed flow visualization in a pump-turbine under off-design operating conditions

François Avellan, Mohamed Farhat, Vlad Hasmatuchi, Steven Roth

The flow hydrodynamics in a low specific speed radial pump-turbine reduced scale model is experimentally investigated under off-design operating conditions in generating mode. Wall pressure measurements, in the stator, synchronized with high-speed flow vis ...

International Association For Hydraulic Research2010

Optimal Control of Part Load Vortex Rope in Francis Turbines

François Avellan, François Gallaire, Simon Pasche

The mitigation of the precessing vortex core developing in the draft tube of Francis turbines operating under part load conditions is crucial to increase the operation flexibility of these hydraulic machines to balance the massive power production of inter ...

ASME2019

On the Efficiency Alteration Mechanisms Due to Cavitation in Kaplan Turbines

François Avellan, Sebastián Camilo Leguizamón Sarmiento

A transport-equation-based homogeneous cavitation model previously assessed and validated against experimental data is used to investigate and explain the efficiency alteration mechanisms in Kaplan turbines. On the one hand, it is shown that the efficiency ...

2017

SURFACE ROUGHNESS IMPACT ON FRANCIS TURBINE PERFORMANCES AND PREDICTION OF EFFICIENCY STEP UP

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

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 ...

2009

Numerical and experimental evidence of the inter-blade cavitation vortex development at deep part load operation of a Francis turbine

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

Francis turbines are subject to various types of the cavitation flow depending on the operating condition s. In order to compensate for the stochastic nature of renewable energy sources, it is more and more required to extend the operating range of the gen ...

International Association For Hydraulic Research2016

Space and time reconstruction of the precessing vortex core in Francis turbine draft tube by 2D-PIV

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

Francis turbines operating at part load conditions experience the development of a high swirling flow at the runner outlet, giving rise to the development of a cavitation precessing vortex rope in the draft tube. The latter acts as an excitation source for ...

International Association For Hydraulic Research2016

RANS computations for identification of 1-D cavitation model parameters: application to full load cavitation vortex rope

François Avellan, Christophe Nicolet, Andres Müller, Sébastien Alligné

Due to the massive penetration of alternative renewable energies, hydropower is a key energy conversion technology for stabilizing the electrical power network by using hydraulic machines at off design operating conditions. At full load, the axisymmetric c ...

International Association For Hydraulic Research2016

Dynamic behaviour of a Francis turbine during voltage regulation in the electrical power system

François Avellan, Elena Vagnoni

Hydroelectric units can be operated in synchronous condenser mode to provide reactive power to the electrical power system (EPS) for voltage regulation. In this operating mode, the hydraulic turbine consumes active power and in case of hydroelectric units ...

2020

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

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

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

Unsteady Numerical Simulations of the Flow Related to the Unstable Energy-Discharge Characteristic of a Medium Specific Speed Double Suction Pump

François Avellan, Philippe Dupont

Regions of positive slope in the pressure-discharge characteristics can result in a reduction or even lack of damping of system instabilities. They are therefore one of the major concerns in design and operation of centrifugal pumps as they are limiting th ...

2007

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

Experimental investigation of the sloshing motion of the water free surface in the draft tube of a Francis turbine operating in synchronous condenser mode

François Avellan, Arthur Tristan Favrel, Loïc Andolfatto, Elena Vagnoni

Hydropower units may be required to operate in condenser mode to supply reactive power. In this operating mode, the water level in the turbine or pump-turbine is decreased below the runner by closing the guide vanes and injecting pressurized air. While ope ...

2018

Experimental method for the evaluation of the dynamic transfer matrix using pressure transducers

François Avellan, Andres Müller, Keita Yamamoto

This paper introduces an experimental method for the evaluation of dynamic transfer matrices using only pressure transducers. The discharge fluctuations are evaluated from the fluctuation of the pressure difference at different streamwise locations. The tr ...

Taylor & Francis Ltd2015