Publications de François Avellan

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Numerical simulations of the transient operation of an islanded power network subject to load rejections are performed. The islanded power network case study consists of a 1-GW hydroelectric power plant featuring four generating units, a long penstock, and ...

For seamless integration of growing electricity production from intermittent renewable energy sources, Francis turbines are under increasing demand to extend their operating range. This requires Francis turbines to operate under off-design conditions, wher ...

At low flow rate operation, Francis turbines feature a cavitating vortex rope in the draft tube resulting from the swirling flow of the runner outlet. The unsteady pressure field related to the precession of the vortex rope induces plane wave propagating i ...

An analytical approach allowing modelling transient phenomena in pipes, valves, surge tanks and Francis turbines based on impedance method is developed. These models are implemented in a software called “SIMSEN”, which simulates the behaviour of complex applications in the domain of adjustable speed drives and electrical power networks. This program is based on a modular structure, which enables the numerical simulation of transient modes of systems exhibiting arbitrary topologies. The numerical simulation

In pipe systems, pressure and flow fluctuations below cutoff frequency propagate as plane waves along pipes. Depending on the pipe length and propagation velocity, resonance leading to high amplitude pressure fluctuation may occur. At low pressure, cavitat ...

An experimental investigation of the rotating stall in reduced scale model of a low specific speed radial pump-turbine at runaway and turbine brake conditions in generating mode is achieved. Measurements of wall pressure in the stator are performed along w ...

The Finite Volume Particle Method (FVPM) is a meshless method for simulating fluid flows which includes many of the desirable features of mesh-based finite volume methods. FVPM benefits from particle interaction vectors to weight conservative fluxes exchan ...

changes and loses its coherence, leading to a drastic reduction in the intensity of the induced excitation source. Francis turbines operating at part-load experience the development of a precessing cavitation vortex rope at the runner outlet, which acts as ...

The hydraulic design of Francis turbines and pump-turbines is an expensive project-specific engineering effort that typically involves a direct iterative exploration of the design space. An inverse design method for turbomachinery has been previously intro ...

Numerical simulation and stability analysis of an islanded power network comprising 40 MW of hydropower, 20 MW of wind power and 60 MW of gas-fired power plant are investigated. First, the modeling of each power plant is fully described. The wind farm is m ...

PSP (Pumped-storage power plants) represent the only mature option for large-scale electricity storage, and offer a wide range of grid management services, ranging from peak power production to ancillary services. This technology has undergone drastic prog ...

The erosion of hydraulic machines by solid particle impacts is a widespread problem that leads to outage for expensive repairs, efficiency reduction, and cavitation enhancement. Numerical simulations can be used to study the phenomenon, provided they featu ...

Nowadays, the pump-storage power plants are a proven solution for storing electricity at large scale and offering flexibility to the power management. Therefore, the hydraulic machines are increasingly subject to off-design operation, start-up and shutdown ...

Francis turbines operating at part load conditions develop a cavitation precessing vortex known as a vortex rope in the draft tube cone below the runner outlet. At part load conditions, this vortex precession acts as an excitation source inducing pressure ...

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 ...

On the basis of experimental studies on the influence of the test head and the water nuclei content on the performance of a Francis turbine, we have shown that outlet cavitation is influenced by the active nuclei content of the test loop water. Numerical simulations of the cavitation nuclei dynamics in a Francis runner allowed us to associate the leading role played by the water nuclei content in the development of outlet cavitation, with the particular pressure distribution over the blades. It was found th

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 ...

To get rid of all numerical aspects in flow simulation results and to have more informations about the evolution of the physical values inside the computational domain, we have developed a controlling and analysing method of these results. This method is based on the physical conservation laws. The balances are computed on the external surfaces of the computational domain and on a liquid surface moving along the main flow direction. The use of this method is iliustrated in the case of an Euler code. This me

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 ...

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 ...

François Avellan

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High-Order Modeling of Hydraulic Power Plant in Islanded Power Network

Physical Mechanism of Interblade Vortex Development at Deep Part Load Operation of a Francis Turbine

Methodology for Risk Assessment of Part Load Resonance in Francis Turbine Power Plant

New Tools for the Simulation of Transient Phenomena in Francis Turbine Power Plants

Cavitation influence on hydroacoustic resonance in pipe

Experimental Evidence of Rotating Stall in a Pump-Turbine at Off-Design Conditions in Generating Mode

Development of a finite volume particle method for 3-D fluid flow simulations

Study of the vortex-induced pressure excitation source in a Francis turbine draft tube by particle image velocimetry

Open-Source Implementation and Validation of a 3D Inverse Design Method for Francis Turbine Runners

Influence of the Hydraulic System Layout on the Stability of a Mixed Islanded Power Network

Study of the drivers and asset management of pumped-storage power plants historical and geographical perspective

FVPM numerical simulation of the effect of particle shape and elasticity on impact erosion

Non-Linear Stability Analysis of a Reduced Scale Model Pump-Turbine at Off-Design Operation

Procedure for predicting part load resonance in Francis turbine hydropower units based on swirl number and local cavitation coefficient similitude

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

Similarity rules of cavitation tests : the case of the Francis turbine

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

Hydraulic analysis of flow computation results

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

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