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Mohamed Farhat

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Publications associées (118)

Hydrodynamic mechanisms of aggressive collapse events in leading edge cavitation

Mohamed Farhat, Ali Amini

Transient cavities generated from unsteady leading-edge cavitation may undergo aggressive collapses which are responsible for cavitation erosion. In this paper, we studied the hydrodynamic mechanisms of these events in the leading edge cavitation formed ov ...

SPRINGER2020

High-speed imaging of high pressures produced by cavitation bubbles

Mohamed Farhat, Danail Obreschkow, Outi Supponen

Cavitation bubbles, when correctly tuned, may provide interesting mechanical and chemical effects to their surroundings owing to their violent collapse. Such an event may produce high-speed liquid jetting, extreme heating, as well as pressures of thousands ...

SPIE-INT SOC OPTICAL ENGINEERING2019

Detailed experiments on weakly deformed cavitation bubbles

Mohamed Farhat, Danail Obreschkow, Nicolas Dorsaz, Philipp Kobel, Outi Supponen

We present high-precision experiments conducted with the aim to better characterise weak deformations of single cavitation bubbles. Using two needle hydrophones and a high-speed photodetector, we record the timings of shock waves and luminescence emitted a ...

SPRINGER2019

LES investigation of the influence of cavitation on flow patterns in a confined tip-leakage flow

Mohamed Farhat, Huaiyu Cheng

In the present paper, Large Eddy Simulations combined with the Zwart-Gerber-Belamri cavitation model are conducted to study the flow characteristics in a tip-leakage flow. A reasonable agreement is obtained between the numerical and experimental data. With ...

PERGAMON-ELSEVIER SCIENCE LTD2019

On the physical mechanism of tip vortex cavitation hysteresis

Mohamed Farhat, Martino Reclari, Matthieu Dreyer, Ali Amini

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

Neurovascular stent artifacts in 3D-TOF and 3D-PCMRI: Influence of stent design on flow measurement

Mohamed Farhat, Pierre Bouillot, Hasan Yilmaz

Purpose: The morphological and hemodynamic evaluations of neurovascular diseases treated with stents would benefit from noninvasive imaging techniques such as 3D time-of-flight MRI (3D-TOF) and 3D phase contrast MRI (3D-PCMRI). For this purpose, a comprehe ...

WILEY2019

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

Mohamed Farhat, Ali Amini

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 ...

PERGAMON-ELSEVIER SCIENCE LTD2019

Gravity-Independent Oscillate Boiling

Mohamed Farhat, Outi Supponen

Heat transfer in nucleate boiling relies on the detachment and rise of the boiling bubble, in which gravity plays the dominant role. Previous studies showed that in the absence of gravity, the bubble fails to rise, causing the dryout of the heater and sign ...

SPRINGER2019

Cavitation induction by projectile impacting on a water jet

Mohamed Farhat

The present paper focuses on the simulation of the high-velocity impact of a projectile impacting on a water-jet, causing the onset, development and collapse of cavitation. The simulation of the fluid motion is carried out using an explicit, compressible, ...

PERGAMON-ELSEVIER SCIENCE LTD2019

Suppressing tip vortex cavitation by winglets

Mohamed Farhat, Martino Reclari, Ali Amini

Despite the numerous remedies prescribed so far, tip vortex cavitation (TVC) remains a major issue in design and operation of diverse applications. In this paper, we experimentally investigate the effectiveness of winglets in suppressing TVC. An elliptical ...

SPRINGER2019

On the hysteresis of cavitation incipience and desinence in hydraulic machines

Mohamed Farhat, Martino Reclari, Ali Amini

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 PUBLISHING LTD2019

Roll-up region of tip vortex: numerical investigation

Mohamed Farhat, Azin Amini, Martino Reclari, Matthieu Dreyer, Ali Amini

The appearance of gas-filled vortices at the tip of hydraulic machines blades is usually associated with increase of losses, vibrations, noise and erosion risk. The understanding of the roll-up region, where the boundary layer on the pressure side crosses ...

IOP PUBLISHING LTD2019

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

How Flow Reduction Influences the Intracranial Aneurysm Occlusion: A Prospective 4D Phase-Contrast MRI Study

Mohamed Farhat, Philippe Reymond, Pierre Bouillot

BACKGROUND AND PURPOSE: Flow-diverter stents are widely used for the treatment of wide-neck intracranial aneurysms. Various parameters may influence intracranial aneurysm thrombosis, including the flow reduction induced by flow-diverter stent implantation, ...

American Society of Neuroradiology (ASNR)2019

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

RANS computations of a confined cavitating tip-leakage vortex

Mohamed Farhat, Matthieu Dreyer

Cavitating tip-leakage vortices appear in several hydrodynamic flows such as marine propellers or Kaplan turbines. Cavitating computations are a challenging topic since several keys issues are an ongoing work such as the definition of a universal mass sour ...

2018

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

Rebounds of deformed cavitation bubbles

Mohamed Farhat, Danail Obreschkow, Outi Supponen

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 ...

AMER PHYSICAL SOC2018

Shock waves from nonspherical cavitation bubbles

Mohamed Farhat, Danail Obreschkow, Nicolas Dorsaz, Philipp Kobel, Marc Tinguely, Outi Supponen

We present detailed observations of the shock waves emitted at the collapse of single cavitation bubbles using simultaneous time-resolved shadowgraphy and hydrophone pressure measurements. The geometry of the bubbles is systematically varied from spherical ...

Amer Physical Soc2017

Luminescence from cavitation bubbles deformed in uniform pressure gradients

Mohamed Farhat, Danail Obreschkow, Philipp Kobel, Outi Supponen

Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single-collapse luminescence. Our innovative measurement system captures a broad luminescence spectrum (wavelengt ...

2017

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