Publications de Mohamed Farhat

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We investigated the flow modifications induced by a large panel of commercial-off-the-shelf (COTS) intracranial stents in an idealized sidewall intracranial aneurysm (IA). Flow velocities in IA silicone model were assessed with and without stent implantati ...

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 ...

The Cavitation Erosion Power based on the assumption that severe erosion is often due to the repeated collapse of the traveling vortex generated by a leading edge cavity has been formerly introduced. We have shown that cavitation erosion intensity may be scaled by a simple set of flow parameters depending on the mean upstream velocity U, the Strouhal number St corresponding to the main cavity fluctuations, the cavity length I and the pressure in the cavity closure. Further tests have been done to validate t

Presented here are experiments clarifying how the deformation of cavitation bubbles affects their rebound. Rebound bubbles carry the remaining energy of a bubble following its initial collapse, which dissipates energy mainly through shock waves, jets, and ...

This paper describes vibration analysis techniques that have been adapted and used to classify cavitation in a model Francis turbine. This analysis can be used to compliment standard cavitation tests. Cavitation can be classified in various ways using vibration analysis. Cavitation attached to the blades of the runner is modulated by instabilities caused by the interaction with the blades and the guide vanes, as well as by the outlet swirl. The shape of this modulation is not sinusoidal. Cavitation on the r

The experimental investigation of the hydrodynamics of a reversible pump-turbine reduced scale model in off-design operating conditions is presented. The onset and development of flow instabilities outside the “normal” operating range, in generating mode, involving runaway and “S-shape”, are described. Wall pressure measurements, in the stator, are performed with the help of miniature piezoresistive sensors synchronized with high speed flow visualizations in the vaneless gap between the impeller and the gui

The prediction of flow diverter stent (FDS) implantation for the treatment of intracranial aneurysms (IAs) is being increasingly required for hemodynamic simulations and procedural planning. In this paper, a deployment model was developed based on geometri ...

A previous report by the present authors [1] clarified the diffuser effect of the draft tube and the effects of swirl in the runner downstream on the hydraulic instabilities in power generation plants. The present study was intended to study the effect of ...

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 ...

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 ...

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 ...

Leading-edge cavitation is responsible of the generation of transient cavities, usually made of clouds of bubbles. These transient cavities travel downstream to high-pressure regions and collapse violently, leading to noise and vibration as well as erosion ...

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 ...

In the present study, a high energy pulsed laser is used to generate a millimetric cavitation bubble within a water flow over a symmetric hydrofoil. The bubble is initiated at different locations in the vicinity of the hydrofoil leading edge. A high-speed camera is used to observe the motion and the deformation of the bubble as it travels along the hydrofoil suction side. We have found that the pressure gradient plays a major role on the bubble dynamic and subsequent phenomena. For a specific region of the

Be it to aerate a glass of wine before tasting, to accelerate a chemical reaction, or to cultivate cells in suspension, the “swirling” (or orbital shaking) of a container ensures good mixing and gas exchange in an efficient and simple way. Despite being used in a large range of applications this intuitive motion is far from being understood and presents a richness of patterns and behaviors which has not yet been reported. The present research charts the evolution of the waves with the operating parameters i

Cavitation within a tip leakage flow remains a challenging issue in a variety of axial hydraulic machines. It is still not possible nowadays to predict cavitation occurrence in such a flow with acceptable accuracy. In the present study, we have carried out ...

We propose an experiment for studying the final stages of collapse of a single laser generated cavitation bubble in microgravity. Unlike previous investigations, the goal of the study is to examine the direct effects of gravity on the cavity collapse. In this paper we present ground-based research on these effects and outline a microgravity experiment destined for ESA Microgravity Research Campaign. The proposed experiment uses a focused laser to generate a highly spherical bubble in an extended water volum

In this first part of a 2 papers series, we present the experimental procedure for onboard measurement of pressure and strain fluctuation in a model of low head Francis turbine. 28 miniature pressure sensors are fitted in the pressure and suction sides of two consecutive blades. A specific technique for sensors mounting has been developed allowing a direct manufacturing of the pressure sensors in the runner blades. This prevents from any geometry alteration of the hydraulic profile. Furthermore, miniature p

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 ...

In the present study, a CFD model for cavitation simulation have been investigated and compared to experimental results in the case of 3-bladed industrial inducer. The model uses a multiphase approach, based on multiphase mixture assumption. A truncated form of Rayleigh-Plesset equation is used as a source term for the inter-phase mass transfer. The model allows a good prediction of the cavitation inception as well as the main cavity dimensions. The threshold corresponding to the head drop is also well pred

Mohamed Farhat

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Particle Imaging Velocimetry Evaluation of Intracranial Stents in Sidewall Aneurysm: Hemodynamic Transition Related to the Stent Design

Efficient and reproducible mammalian cell bioprocesses without probes and controllers?

Cavitation erosion power as a scaling factor for cavitation erosion of hydraulic machines

Rebounds of deformed cavitation bubbles

Classification of Cavitation in Hydraulic Machines using Vibration Analysis

Hydrodynamics of a Pump-Turbine under Off-Design Operating Conditions in Generating Mode

Geometrical deployment for braided stent

One-dimensional analysis of full load draft tube surge

Cavitation bubble behavior inside a liquid jet

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

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

Numerical and experimental investigation of shedding mechanisms from leading-edge cavitation

Cavitation Bubble Dynamics inside Liquid Drops in Microgravity

Laser-induced cavitation bubble collapsing in the vicinity of the leading edge of a hydrofoil

Surface wave dynamics in orbital shaken cylindrical containers

Large eddy simulation of the tip-leakage cavitating flow with an insight on how cavitation influences vorticity and turbulence

Direct effects of gravity on cavitation bubble collapse

Onboard Measurements of Pressure and Strain Fluctuations in a Model of low Head Francis Turbine. Part 1 : Instrumentation

Dynamics and Intensity of Erosive Partial Cavitation

Experimental and Numerical Cavitation Flow Analysis of an Industrial Inducer