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Mohamed Farhat

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Publications associées (118)

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

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

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

François Avellan, Mohamed Farhat, Eduard Egusquiza

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

2D Oscillating Hydrofoil

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

This paper presents a validation of numerical simulations in case of a forced oscillating hydrofoil. As a representative case study for vibrating blade in hydraulics machines, a 2D NACA 0009 oscillating hydrofoil is considered. Pressure coefficients from e ...

2007

Unsteady CFD Prediction of von Kármán Vortex Shedding in Hydraulic Turbine Stay Vanes

François Avellan, Mohamed Farhat, Philippe Ausoni

All hydraulic turbines containing a casing with stay vanes face the potential dynamic problem of stay vane von Kármán vortex shedding. For hydraulic efficiency purposes the stay vanes tend to be relatively slender in the direction normal to the flow thus b ...

2007

Dynamics and Intensity of Erosive Partial Cavitation

François Avellan, Mohamed Farhat, Eduard Egusquiza

An experimental work has been carried out to investigate the dynamic behavior and the intensity of erosive partial cavitation on a 2-D hydrofoil. Both sheet (stable) and cloud (unstable) cavitation have been tested in a cavitation tunnel for various free s ...

2007

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

François Avellan, Philippe Dupont, Mohamed Farhat, Stefan Berten

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

Hydrofoil Roughness Effects on von Kármán Vortex Shedding

François Avellan, Mohamed Farhat, Philippe Ausoni

The shedding process of the von Kármán vortices is shown to be highly related to the state of the boundary layer over the entire hydrofoil: The selected hydrofoil has a laminar-turbulent boundary layer transition at mid-chord for an incidence angle of 0° a ...

2007

Interaction of a cavitation bubble with a spherical free surface

Mohamed Farhat, Danail Obreschkow, Nicolas Dorsaz, Philipp Kobel, Aurèle De Bosset

The dynamic of a cavitation bubble inside a water drop is investigated in microgravity in order to analyze the interaction between the collapsing bubble and a quasispherical free surface. Tests are carried in the frame of the 42nd parabolic flight campaign ...

2006

Flow in a Pelton Turbine Bucket: Numerical and Experimental Investigations

Alexandre Perrig, François Avellan, Mohamed Farhat

The aim of the paper is to present the results of investigations conducted on the free surface flow in a Pelton turbine model bucket. Unsteady numerical simulations, based on the two-phase homogeneous model, are performed together with wall pressure measur ...

2006

Pump-Turbine Rotor-Stator Interactions in Generating Mode: Pressure Fluctuation in Distributor Channel

François Avellan, Mohamed Farhat, Amirreza Zobeiri

Investigation of the rotor-stator interactions of a reduced-scale model 0.19 ν= pump-turbine in generating mode is presented for the maximum discharge operating condition. This operating point is chosen in order to have the most important rotor-stator inte ...

International Association For Hydraulic Research2006

On the Dynamic of Cavitation Bubbles and Their Interaction with Solid and Free Surfaces

Mohamed Farhat

The cavitation phenomenon, which is due to a pressure drop in liquid flows, may be responsible of noise and vibration as well as efficiency alteration and material erosion. A tremendous work has been already performed to better understand the onset and dev ...

2006

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

François Avellan, Mohamed Farhat, Philippe Ausoni, 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

Cavitation Bubble Dynamics inside Liquid Drops in Microgravity

Claude Nicollier, Mohamed Farhat, Danail Obreschkow, Nicolas Dorsaz, Philipp Kobel, Aurèle De Bosset

We report a fundamental study of single cavitation bubbles inside quasi-spherical water drops produced in microgravity (42nd ESA parabolic flight campaign, 8th ESA student parabolic flight campaign). High-speed imaging revealed implications of isolated, fi ...

2006

Cavitation in Kármán Vortices and Flow Induced Vibrations

François Avellan, Mohamed Farhat, Philippe Ausoni

The shedding process of the Kármán vortices at the trailing edge of a 2D hydrofoil at high Reynolds numbers is investigated. The focus is put on the effect of the cavitation on the vortex street morphology. A direct insight is also provided on the role of ...

2006

Cavitation effects on fluid-structure interaction in the case of a 2D hydrofoil

François Avellan, Mohamed Farhat, Philippe Ausoni

In the present study, we have carried out an experimental investigation on the fluid-structure interaction caused by Karman vortices in the wake of a truncated 2D hydrofoil. The instrumentation involves a high frequency accelerometer and high speed visuali ...

2005

Numerical Flow Analysis in a Pelton Turbine Bucket

Alexandre Perrig, François Avellan, Mohamed Farhat

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 ...

International Association For Hydraulic Research2004

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