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Mohamed Farhat

Cette personne a quitté l’EPFL

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Publications associées (118)

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Gyroid as a novel approach to suppress vortex shedding and mitigate induced vibration

Thomas Antoine Nicolas Berger, Mohamed Farhat

The present study uncovers how a Gyroid-structured extension, attached to a hydrofoil trailing edge, may prevent the formation of Karman vortices and remarkably reduce vortex-induced vibration (VIV). The case study is a blunt truncated NACA 0009 hydrofoil ...

2025

Jetting from cavitation bubbles due to multiple shockwaves

Mohamed Farhat, Outi Supponen

We present experimental observations of microjets formed by cavitation microbubbles. An underwater electric discharge, applied beneath a flat free surface, produces a primary compression wave, which undergoes several phase inversions upon reflections from ...

AMER INST PHYSICS2018

Dynamics of cavitation bubbles near granular boundaries

Mohamed Farhat, Davide Bernardo Preso, Armand Baptiste Sieber

We study the dynamics of a cavitation bubble near beds of sand of different grain sizes. We use high-speed imaging to observe the motion of the bubble and the sand for different values of the stand-off parameter gamma (dimensionless bubble-boundary distanc ...

Cambridge University Press2022

Vortex shedding from a composite hydrofoil: Experimental evidence of a novel "partial lock-in"

Thomas Antoine Nicolas Berger, Mohamed Farhat

Lock-in is of great importance in many engineering applications due to its practical implications for structural safety. The influence of composite bend-twist coupling on the wake dynamics and vortex-induced vibration around a carbon fiber composite hydrof ...

Aip Publishing2023

On the hysteresis of cavitation incipience and desinence in hydraulic machines

Mohamed Farhat, Ali Amini, Martino Reclari

The omnipresent vortical structures in hydraulic machines are extremely prone to the occurrence of cavitation. It is well known that besides the flow parameters, the incipience, development, and disappearance of cavitation within a vortex is very sensitive ...

IOP Publishing2019

On the physical mechanism of tip vortex cavitation hysteresis

Mohamed Farhat, Matthieu Dreyer, Ali Amini, Martino Reclari

Inception and desinence thresholds of tip vortex cavitation (TVC), generated by an elliptical NACA 16-020 hydrofoil, are measured at different flow conditions for various gas contents. It is observed that TVC often disappears at cavitation indices signific ...

SPRINGER2019

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

François Avellan, Mohamed Farhat, 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

Mitigating tip vortex cavitation by a flexible trailing thread

Mohamed Farhat, Ali Amini

Tip Vortex Cavitation (TVC) is a major issue in design and operation of axial hydraulic machines. We investigate the capacity of a flexible trailing thread in alleviating TVC by analyzing the flow-induced motion. For this purpose, a nylon thread with three ...

AMER INST PHYSICS2019

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

François Avellan, Mohamed Farhat

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

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

François Avellan, Mohamed Farhat, Philippe Dupont

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

High-speed flow visualization in a pump-turbine under off-design operating conditions

François Avellan, Mohamed Farhat, Vlad Hasmatuchi, Steven Roth

The flow hydrodynamics in a low specific speed radial pump-turbine reduced scale model is experimentally investigated under off-design operating conditions in generating mode. Wall pressure measurements, in the stator, synchronized with high-speed flow vis ...

International Association For Hydraulic Research2010

Signal analysis of an actively generated cavitation bubble in pressurized pipes for detection of wall stiffness drops

Anton Schleiss, Giovanni De Cesare, Mohamed Farhat, Alexandre Jean Pachoud, Fadi Hachem

Due to the increasing production of volatile new renewable energies as solar and wind, storage hydropower plants have to operate under harsh operation conditions in order to stabilize the electricity grid. As a result, highly transient water pressures occu ...

Elsevier2016

Modal behavior of a reduced scale pump-turbine impeller. Part 1: Experiments

François Avellan, Mohamed Farhat

An experimental investigation has been carried out to quantify the effects of surrounding fluid on the modal behavior of a reduced scale pump-turbine impeller. The modal properties of the fluid-structure system have been obtained by Experimental Modal Anal ...

International Association For Hydraulic Research2010

Computational fluid dynamics with stents: quantitative comparison with particle image velocimetry for three commercial off the shelf intracranial stents

Mohamed Farhat, Pierre Bouillot

Background and purpose Validation of computational fluid dynamics (CFD) in stented intracranial aneurysms (IAs) is still lacking, to reliably predict prone to occlusion hemodynamics, probing, in particular, velocity reduction, and flow pattern changes. Thi ...

Bmj Publishing Group2016

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

3D phase contrast MRI: Partial volume correction for robust blood flow quantification in small intracranial vessels

Mohamed Farhat, Pierre Bouillot

Purpose: Recent advances in 3D-PCMRI (phase contrast MRI) sequences allow for measuring the complex hemodynamics in cerebral arteries. However, the small size of these vessels vs spatial resolution can lead to non-negligible partial volume artifacts, which ...

Wiley2018

Ex uno plures: how to construct high-speed movies of collapsing cavitation bubbles from a single image

Mohamed Farhat, Davide Bernardo Preso, Armand Baptiste Sieber

The time-resolved visualization of the dynamics of a cavitation bubble usually requires the use of expensive high-speed cameras, which often provide a limited spatial resolution. In the present study, we propose an alternative to these high-speed imaging t ...

Springer2023

On the numerical simulation of a confined cavitating tip leakage vortex under geometrical and operational uncertainties

Mohamed Farhat

The effects of operational and geometrical uncertainties on Tip Leakage Vortex (TLV) characteristics are investigated in the current research. Geometrical uncertainties are comprised of manufacturing tolerances or gradual geometry degradation over the time ...

PERGAMON-ELSEVIER SCIENCE LTD2021

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

Simulation of bubble expansion and collapse in the vicinity of a free surface

Mohamed Farhat, Outi Supponen

The present paper focuses on the numerical simulation of the interaction of laser-generated bubbles with a free surface, including comparison of the results with instances from high-speed videos of the experiment. The Volume Of Fluid method was employed fo ...

Amer Inst Physics2016