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Mohamed Farhat

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Publications associées (118)

Comminution limit (CL) of particles and possible implications for pumped storage reservoirs

Mohamed Farhat

Comminution (fragmentation) of solid particles is important in a range of technologies. An interesting effect is the so-called comminution limit (CL), which is effectively a brittle/ductile transition. Above the CL particles fail by fracture. However, as p ...

Springer2014

Hysteresis phenomena in hydraulic measurement

Mohamed Farhat, Hongjuan Ran

Hysteresis phenomena demonstrate the lag between the generation and the removal of some physical phenomena. This paper studies the hysteresis phenomena of the head-drop in a scaled model pump turbine using experiment test and CFD methods. These lag is indu ...

Iop Publishing Ltd2013

A self-assembled three-dimensional cloak in the visible

Mohamed Farhat, Alastair Cunningham, Toralf Scharf

An invisibility cloak has been designed, realized and characterized. The cloak hides free-standing sub-wavelength three-dimensional objects at the short wavelength edge of the visible spectrum. By a bottom-up approach the cloak was self-assembled around th ...

Nature Publishing Group2013

Evidence for hydrogen generation in laser- or spark-induced cavitation bubbles

Mohamed Farhat, Marc Tinguely

The growing use of focused lasers or electric sparks to generate cavitation bubbles raises concerns about the possible alteration of gas content during the initiation process and its effect on bubble dynamics. We provide experimental evidence that hydrogen ...

American Institute of Physics2013

The quest for the most spherical bubble: experimental setup and data overview

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

We describe a recently realized experiment producing the most spherical cavitation bubbles today. The bubbles grow inside a liquid from a point plasma generated by a nanosecond laser pulse. Unlike in previous studies, the laser is focussed by a parabolic m ...

Springer Verlag2013

Experimental investigation of added mass effects on a hydrofoil under cavitation conditions

Mohamed Farhat, Eduard Egusquiza

The influence of leading edge sheet cavitation and supercavitation on the added mass effects experienced by a 2-D NACA0009 truncated hydrofoil has been experimentally investigated in a hydrodynamic tunnel. A non-intrusive excitation and measuring system ba ...

Elsevier2013

Energy partition at the collapse of spherical cavitation bubbles

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

Spherically collapsing cavitation bubbles produce a shock wave followed by a rebound bubble. Here we present a systematic investigation of the energy partition between the rebound and the shock. Highly spherical cavitation bubbles are produced in micrograv ...

American Physical Society2012

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

François Avellan, Mohamed Farhat, Eduard Egusquiza, Xiaopeng Huang

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 ...

International Association For Hydraulic Research2012

The Effects of a Tripped Turbulent Boundary Layer on Vortex Shedding from a Blunt Trailing Edge Hydrofoil

François Avellan, Mohamed Farhat, Philippe Ausoni, Amirreza Zobeiri

Experiments on vortex shedding from a blunt trailing edge symmetric hydrofoil operating at zero angle of attack in a uniform high speed flow, Re-h = 16.1 . 10(3) - 96.6 . 10(3), where the reference length h is the trailing edge thickness, are reported. The ...

2012

Analytical approximations for the collapse of an empty spherical bubble

Mohamed Farhat, Danail Obreschkow

The Rayleigh equation 3/2 (R) over dot + R(R) double over dot + p rho(-1) = 0 with initial conditions R(0) = R-0, (R) over dot(0) = 0 models the collapse of an empty spherical bubble of radius R(T) in an ideal, infinite liquid with far-field pressure p and ...

2012

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

François Avellan, Mohamed Farhat, Philippe Ausoni, Amirreza Zobeiri

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 ...

Elsevier2012

Cavitation in impacted drops and jets and the effect on erosion damage thresholds

Mohamed Farhat, Danail Obreschkow, Marc Tinguely

It is well known that metals and alloys erode at lower impact threshold velocities than expected. This was studied by Thomas and Brunton (1970) who reported “discrepancy factors” in the range 4–10. These authors suggested that liquid impact was a more sear ...

Elsevier Science Sa2012

Hydrodynamic stress in orbitally shaken bioreactors

Florian Maria Wurm, Lucia Baldi Unser, Alfio Quarteroni, Mohamed Farhat, Marco Discacciati, David Hacker, Stéphanie Tissot, Martino Reclari, Samuel Quinodoz, Matthieu Dreyer, Dominique Terry Monteil Jr

2011

Influence of the Pump-Turbine Guide Vanes Vibrations on the Pressure Fluctuations in the Rotor-Stator Vaneless Gap

François Avellan, Mohamed Farhat, Steven Roth, Vlad Hasmatuchi, Francisco Botero

We investigate the Rotor-Stator Interaction in a pump-turbine reduced scale model by considering fluid-structure coupling. The pressure fluctuations amplitude in the rotor-stator vaneless gap has generally been shown to increase linearly with the operating ...

2011

Efficient and reproducible mammalian cell bioprocesses without probes and controllers?

Florian Maria Wurm, Lucia Baldi Unser, Mohamed Farhat, David Hacker, Stéphanie Tissot, Martino Reclari, Matthieu Dreyer, Agata Oberbek

Bioprocesses for recombinant protein production with mammalian cells are typically controlled for several physicochemical parameters including the pH and dissolved oxygen concentration (DO) of the culture medium. Here we studied whether these controls are ...

Elsevier2011

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

François Avellan, Mohamed Farhat, Steven Roth, Vlad Hasmatuchi, Francisco Botero

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 ...

American Society of Mechanical Engineers2011

Confined shocks inside isolated liquid volumes: A new path of erosion?

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

The unique confinement of shock waves inside isolated liquid volumes amplifies the density of shock–liquid interactions. We investigate this universal principle through an interdisciplinary study of shock-induced cavitation inside liquid volumes, isolated ...

American Institute of Physics2011

Bubbles in drops: from cavitation to exploding stars

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

APS2011

Hydrodynamics of a Pump-Turbine at Off-Design Operating Conditions: Numerical Simulation

François Avellan, Mohamed Farhat, Steven Roth, Vlad Hasmatuchi, Francisco Botero

Flow numerical simulations in a low specific speed radial pump-turbine scale model are performed to investigate off-design operating conditions in generating mode. The Best Efficiency Point (BEP) and the runaway operating conditions at 10° guide vanes open ...

2011

Modal behavior of a reduced scale pump turbine impeller. Part II: Numerical simulation

François Avellan, Mohamed Farhat, Eduard Egusquiza, Xiaopeng Huang

A numerical simulation has been carried out to analyze the modal behavior of a reduced scale pump-turbine impeller. The simulation has been done using FEM method, in air and in water. The same boundary conditions than in the experiment were considered: fre ...

International Association For Hydraulic Research2010

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