Publications by François Avellan

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The aim of this study was to provide a complete experimental and numerical analysis of the flow in a rotating Pelton bucket. For the experimental analysis, several functioning points have been used in order to study differences which may occur in various s ...

For the refurbishment projects, one of the most important problems is to evaluate the economical efficiency of the project. It is difficult to estimate, with good accuracy, the hydraulic efficiency in situ for existing configurations and even more difficult to estimate the upgrading of the characteristics after refurbishment. The aim of this paper is to propose a procedure for performance measurement and for the analysis of a turbine characteristics applied on a refurbishment project. By comparative model t

Francis turbines operating at part load condition experience the development of a cavitating helical vortex rope in the draft tube cone at the runner outlet. The precession movement of this vortex rope induces local convective pressure fluctuations and a s ...

This paper presents a mesh adaptation procedure linked to a finite volume solver, the goal of which is to increase the precision of the numerical simulation of a wing tip vortex flow. The adaptation scheme is applied to hexahedron meshes and hybrid meshes ...

The electrochemical cavitation detection technique has been used to locate and measure the instantaneous cavitation erosion rate on a 2D NACA profile tested in the IMHEF high-speed cavitation tunnel. Nineteen titanium probes, flush mounted along the profile suction side could monitor during the test thee local and instantaneous erosion rate with a detection limit as low as 0 .02 mm per year of titanium grade 2. Pressure measurements have been also made as well as high-speed photography. The operating condio

At full load, pump-turbines operating in generating mode may experience a cylindrical cavitation vortex rope caused by the swirling flow in the draft tube cone. Under certain conditions, this vortex rope initiates both pressure and power oscillations. The ...

The numerical investigation of the unsteady flow patterns around a Pelton bucket can be helpful to improve the overall turbine efficiency by optimizing the bucket design based on identified loss mechanisms. Since the flow is highly turbulent, modeling the ...

An experimental study of flow in a Francis hydraulic turbine, especially designed for the GAMM Workshop, has been carried out. In order to provide a data base for the validation and comparison of computational fluid dynamics codes, a Francis turbine mode! and adequate instrumentation have been specially developed. Measurements of both global and local quantities have been performed for the best operating point of the turbine. A five-hole probe mounted on a remote traversing system provides static pressure a

Three dimensional numerical tools are now commonly used in the design or analysis process of the internai flow of hydraulic machinery. As an illustration of the use of such tools to study the internai flow of a Francis turbine, the computational results obtained in all components of this turbine with an Euler equations solver and two Reynolds Averaged Navier Stokes equations solvers are discussed. The analysis process is illustrated and comparisons with experimental results obtained in the spiral casing and

When in operation, pump-turbine runners have to withstand large pressure pulsations generated by the rotor-stator interaction. The analysis of the dynamic behavior of these structures is necessary to avoid damage. For this analysis a realistic model of the ...

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 ...

Experimental flow analysis of hydraulic machines is of prime importance for improving the design of such a unit. Moreover, computational fluid dynamics codes need an experimental data reference in order to check their ability to simulate the main flow features. To obtain such an experimental data base a Francis turbine model and an associated instrumentation is specially developed. Measurements of both global and local quantities are performed for five different operating points of the turbine. A five-hole

Three different methods of cavitation erosion measurement are compared and correlated with weight loss rates in two cavitation set-ups: a high-pressure cavitation jet producing a high repetition rate of a wide range of impact intensities and a single vortex machine producing a low repetition rate of large collapses. The electrochemical cavitation activated current measurements on pure titanium sensors are calibrated on the jet and used to evaluate erosion rates on the vortex. The cavitation pit counting tec

Most of the severe erosion of hydraulic machines are found to be associated with the collapse of transient cavitation vortices downstream of a leading edge cavity. The dynamics of such a type of cavitation is investigated in a Cavitation Vortex Generator (CVG). By producing the cyclic growth and collapse of single cavitation vortex, this device provides a way to investigate the mechanisms involved in the final stage of the cavity collapse. Very high-speed visualization, at a rate of 500 '000 frames per seco

In the present study, the identification of hydrodynamic damping is investigated in the case of 2D blade placed in the test section of the EPFL High Speed Cavitation Tunnel. A non intrusive technique, based on a spark generated bubble, is used to generate ...

In order to study the inlet and outlet cavitation in a Francis turbine (nq = 48) a numerical model of the bubble dynamics is established. By using the pressure and velocity distribution obtained by a 3-D potential flow analysis of the turbine, the Rayleigh-Plesset equation is integrated for a wide range of head and bubble sizes and for two typical turbine operating points, where inlet and outlet cavitation respectively are observed. The numerical simulations agree very well with the main cavitation features

Francis turbines operating at part load conditions typically experience a cavitation vortex rope immediately at the runner outlet. As the compliance of this cavitation flow is much higher than the one in cavitation-free conditions, a decrease in the value ...

Numerical and Experimental Analysis of Free Surface Flow in a 3D Non-Rotating Pelton Bucket Low frequency fluctuations often occur in hydraulic installations equipped with fixed bladed turbines or pumps operating under off design conditions. Passive measures, such as air admission or minor design modifications, are commonly taken as a last resort to try to reduce these phenomena. This article describes an active control approach to the problem, which is based upon a rotating valve exciter. The idea is to cr

The flow investigation in a elbow draft tube is presented. After a review of the existing works related to the flow analysis of such component, the need of an experimental validation of the CFD tools is discussed with respect the practical interest of improving the matching of a runner and the draft tube. The geometry and the main characteristics of the test model is described and the pressure recovery coefficient is provided in an extended operating range. The instrumentation of the draft tube and the LDA

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. In this paper, we develop a new 3-D FVPM formulation that features spherical kernel ...

François Avellan

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Experimental and Numerical Analysis or Free Surface Flows in a Rotating Bucket

Tests on Reduced Scale Models for the Refurbishment Projects of Hydroelectric Power Plants

Hydro-acoustic resonance behavior in presence of a precessing vortex rope: observation of a lock-in phenomenon at part load Francis turbine operation

Numerical capture of wing tip vortex improved by mesh adaptation

On line measurement of cavitations erosion rate on a 2D NACA profile

Overload Surge Event in a Pumped-Storage Power Plant

GPU-accelerated Pelton turbine simulation using finite volume particle method coupled with linear eddy viscosity models

Experimental flow study of the GAMM turbine model

Comparison of Flow Computation Results with experimental Flow Surveys in a Francis Turbine

Analysis of the dynamic response of pump-turbine runners- Part I: Experiment

Modeling and Numerical Simulation of a Complete Hydroelectric Production Site

Flow survey and blade pressure measurements in a Francis turbine model

Cavitation erosion, impact intensity and pit size distribution of jet and vortex cavitation

Shock pressure generated by cavitation vortex collapse

Hydrodynamic Damping Identification from an Impulse Response of a Vibrating Blade

Theoretical and experimental study of the inlet and outlet cavitation in a model of a Francis turbine

Measurements of Cavitation Compliance in the Draft Tube Cone of a Reduced Scale Francis Turbine Operating at Part Load

Numerical and Experimental Analysis of free Surface Flow in a 3D non Rotating Pelton Bucket

Flow Investigation in a Francis Draft Tube : the Flindt Project

Exact finite volume particle method with spherical-support kernels