Publications by Mohamed Farhat

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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 ...

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 ...

BACKGROUND AND PURPOSE: Intracranial stents have become extremely important in the endovascular management of complex intracranial aneurysms. Sizing and landing zone predictions are still very challenging steps in the procedure. Virtual stent deployment ma ...

Large eddy simulations of tip vortex cavitation (TVC) around an elliptical hydrofoil is performed to study its scale effect. A satisfying agreement is obtained between the numerical and experimental data. It indicates that the scale effect of TVC is remark ...

In the present study, the fluid-structure coupling is investigated in the guide vanes of a pump-turbine scale model placed in one of the test rigs of the Laboratory for Hydraulic Machines (EPFL) in Lausanne. The paper focuses on the advanced instrumentatio ...

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, ...

In centrifugal pumps, the interaction between the rotating impeller blades and the stationary diffuser vanes generates specific pressure fluctuation patterns. At off design operation, high incidence and large local pressure gradients can lead to flow separ ...

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, ...

Different measurement techniques have been used to detect cavitation on a Francis turbine model. The results are compared to those obtained on the prototype and presented in the first of this series of articles. The runner mode! used for that study is built on the basis of a geometrical recovery of one of most eroded blade of the prototype. The results of the different measurements are presented and commented by comparison with prototype measurements. This comparison leads to a proposal of the physics which

This paper presents investigations of unsteady flow conditions influence over cavitation dynamics. Measurements of wall pressure fluctuations in a model turbine are first introduced. It is shown that the wake of the spiral casing tongue modulates cavity dynamics near the trailing edge of runner blades. A new device, which permits a 2D hydrofoil to oscillate around its mean incidence angle, is used in order to recreate flow conditions similar to those of blade row wakes experienced in industrial flows. This

This paper describes the techniques and physical parameters used to produce stable centimetric water drops in microgravity, and to study single cavitation bubbles inside such drops (Parabolic Flight Campaigns, European Space Agency ESA). While the main sci ...

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 ...

In the present study, a high energy pulsed laser is used to generate a millimetric cavitation bubble within a water °ow over a symmetric hydrofoil. The bubble is initiated at di®erent locations in the vicinity of the hydrofoil leading edge. A high speed camera is used to observe the motion of the bubble as it travels along the hydrofoil suction side. Besides the stando® parameter, we have found that the pressure gradient plays a major role on bubble dynamic and subsequent phenomena. For a speci¯c initial lo

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 ...

Cavitation bubbles collapsing and rebounding in a pressure gradient del p form a "microjet" enveloped by a "vapor jet." This Letter presents unprecedented observations of the vapor jets formed in a uniform gravity-induced del p, modulated aboard parabolic flights. The data uncover that the normalized jet volume is independent of the liquid density and viscosity and proportional to zeta equivalent to vertical bar del p vertical bar R-0/Delta p, where R-0 the maximal bubble radius and Delta p is the driving p

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 ...

The tendency of designing large Kaplan turbines with a continuous increase of output power is bringing to the front the cavitation erosion issue. Due to the flow in the gap between the runner and the discharge ring, axial turbine blades may develop the so ...

It is well known that the performance of the turbomachinery (losses, vibrations, noise, and erosion) is often affected by the trailing vortex from the blade tip (Tip Leakage Vortex; TLV) of the impeller or propeller, and sometimes cavitation occurs in the ...

Efficient mixing in bioreactors is essential in order to avoid concentration gradients which can be harmful for mammalian cells. To study mixing and its scalability in orbitally shaken cylindrical bioreactors, we measured mixing times in containers with no ...

Some two-dimensional (2D) exfoliated zeolites are single- or near single-unit cell thick silicates that can function as molecular sieves. Although they have already found uses as catalysts, adsorbents and membranes precise determination of their thickness ...

Mohamed Farhat

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

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

Virtual-versus-Real Implantation of Flow Diverters: Clinical Potential and Influence of Vascular Geometry

Numerical study on the scale effect of tip vortex cavitation induced by incoming velocities and scale ratios

Advanced Instrumentation for Measuring Fluid-Structure Coupling Phenomena in the Guide Vanes Cascade of a Pump-Turbine Scale Model

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

Experimental Investigation of Pressure Fluctuations in a High-Energy Centrifugal Pump Stage at Off-Design Conditions

Cavitation induction by projectile impacting on a water jet

Cavitation Erosion Prediction on Francis Turbines Part 2 : Model Tests and Flow Analysis

The influence of flow unsteadiness on erosive cavity dynamics

Techniques for generating centimetric drops in microgravity and application to cavitation studies

High-speed imaging of high pressures produced by cavitation bubbles

Dynamic of cavitation bubble in a flowing liquid with a pressure gradient

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

Universal Scaling Law for Jets of Collapsing Bubbles

Gravity-Independent Oscillate Boiling

Mind the gap - tip leakage vortex in axial turbines

Effect of the winglet on reduction of blade tip vortex from elliptical hydrofoil

Determination of a scale-up factor from mixing time studies in orbitally shaken bioreactors

RANS computations of tip vortex cavitation