Publications de François Avellan

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The hydroabrasive erosion of hydraulic machine components, especially Pelton buckets and needles, is a widespread problem that entails significant costs. The multiscale nature of the process renders its simulation very computationally demanding unless spec ...

The runner blade-to-blade shear flow turbulent mixing characteristics in the cone of a Francis turbine scale model are investigated by using the 3D PIV Technique. From the experimental flow survey, the periodic component of the instantaneous velocity field is extracted by a phase averaging procedure. This procedure made apparent the main structures of the flow and the mixing process of the incoming shear flow.

The increment of frictional deficiency by roughening the inner wall of spiral case is extracted from the optimum specific hydraulic energy deficiencies of a model Francis turbine that was measured by changing surface roughness of the spiral case. Assuming the free vortex flow in the spiral case, the frictional deficiency is predicted for the smooth and roughened spiral cases. By comparing the predicted deficiency with the measured increment of deficiency due to the roughness increase, the admissible roughne

The effect of hydrofoil trailing edge shape on the wake dynamic and flow induced vibration is investigated at high Reynolds number, Re = 0.5 x 10(6)-2.9 x 10(6). Two NACA 0009 hydrofoils with blunt and oblique trailing edges are tested. The velocity field ...

In the process of developing tools for cavitation erosion prediction of prototypes from mode) tests, 4 on board aggressiveness evaluation methods were tested on a severely eroded blade of a 266 MW Francis turbine. These are pressure, pit counting, DECER electrochemical and vibration measurements. All methods provided coherent results on the blade mounted measurements. The test program provided understanding of the heterogeneous erosion distribution of the prototype blades and quantitative data for compariso

Numerical simulations of water entries based on a three-dimensional parallelized Smoothed Particle Hydrodynamics (SPH) model developed by Ecole Centrale Nantes are presented. The aim of the paper is to show how such SPH simulations of complex 3D problems i ...

The parallel rotor-stator computation capabilities of Fine Turbo and CFX-TASCflow CFD commercial codes have been investigated within the frame of the European ESPRIT project HPNURSA. Unsteady computations have been performed for simple test cases, where fl ...

The authors present the current context for energy transition and hydropower development in Switzerland, summarizing the activities in the field of hydropower infrastructure research carried out over the past three years and presenting the development objectives for the coming four years. The focus is on increasing operational flexibility and winter production. The plan includes three large scale pilot projects, the first on recently commissioned small hydro schemes, the second on sediment release through t

New developments of free surface flows computation have been made by several CFD software companies. Thanks to these developments, new methods such as the Volume of Fluid (VOF) can be now used for the analysis of the free surface flows in various hydraulic machines. However, this method needs an experimental validation. The aim of this study is to experimentally validate the VOF method applied to a case such as the jet impact on a plane wall.

The massive penetration of the electrical network by renewable energy sources, such as wind and solar, pushes the operators to extend hydropower plant units operating range to meet the transmission system operator requirements. However, in off-design opera ...

Structure Interaction (FSI) phenomena is becoming a relevant study field for the design or revamping of hydropower plants. The generalized trend of increasing flow rates and reducing rotor blades/stay vanes thickness in order to improve the efficiency of t ...

The paper presents numerical investigations of decelerated swirling flows specific to hydraulic turbines draft tube cone, within the framework of axisymmetric flow models. First, we investigate the behaviour of a Burgers vortex in a diffuser as the swirl i ...

The flow in the Pelton turbine bucket is three-dimensional, unsteady, turbulent, features a free surface, and is influenced by the rotation-induced forces. It is therefore difficult to investigate how the energy transfer takes place between the water flow ...

The investigation of the rotating stall phenomenon appearing in the HYDRODYNA pump-turbine reduced scale model is carried out by performing a large-scale large eddy simulation (LES) computation using a mesh featuring approximately 85 x 10(6) elements. The ...

The present paper reports the development of Finite Particle Method (FPM) in the framework of 3D impinging jet simulations. The FPM kernel has been proposed recently in the literature to improve the consistency of standard SPH. Moreover, a new particle shifting method is proposed to mitigate the particle clustering issue. The influence of particle spacing, maximum CFL number and different particle shifting methods are investigated in the case of a water jet impinging perpendicularly on a flat plate. The res

To characterize the boundary layer development, in the cone of the Francis turbine, wall friction and velocity measurements are performed. The mean wall friction measurements evidence the increasing risk of the boundary layer separation at the cone wall wi ...

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 ...

An experimental and theoretical investigation of the flow at the outlet of a Francis turbine runner is carried out in order to elucidate the causes of a sudden drop in the draft tube pressure recovery coefficient at a discharge near the best efficiency ope ...

François Avellan

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Simulation of the hydroabrasive erosion of a bucket: A multiscale model with projective integration to circumvent the spatio-temporal scale separation

Experimental Study of the Runner Blade-to-Blade Shear Flow Turbulent Mixing in the Cone of Francis Turbine Scale Model

Effect of Surface Roughness on Hydraulic Loss in Spiral Case

How oblique trailing edge of a hydrofoil reduces the vortex-induced vibration

Cavitation Erosion Prediction on Francis Turbines Part 1 : Measurements on the Prototype

SPH High-Performance Computing simulations of rigid solids impacting the free-surface of water

Unsteady Rotor - Stator Analysis of Hydraulic Pump - Turbine : CFD and Experimental Approach

Electricity supply and hydropower development in Switzerland

Free surface flow : experimental validation of volume of fluid (VOF) method in the plane wall case

Reduced scale model testing for prediction of eigenfrequencies and hydro-acoustic resonances in hydropower plants operating in off-design conditions

Boundary layer effects on the vortex shedding in a Donaldson-type hydrofoil

Numerical Simulation and Analysis of Swirling Flow in the Draft Tube Cone of a Francis Turbine

Numerical Flow Analysis in a Pelton Turbine Bucket

Large Eddy Simulation of the Rotating Stall in a Pump-Turbine Operated in Pumping Mode at a Part-Load Condition

Air-Water Ring in the Vaneless Gap of a Reversible Pump-Turbine Operating in Condenser Mode

FPM Simulations of a 3D Impinging Jet on a Flat Plate Comparison with CFD and Experimental Results

Wall Friction and Boundary Layer Development in the Cone of a Francis Turbine Scale Model

A spherical kernel for the Finite Volume Particle Method and application to surface tension

Transient Behavior of variable speed pump-turbine units

Analysis of the Swirling Flow Downstream a Francis Turbine Runner