Publications associées à Improvement of Acoustic Doppler Velocimetry in steady and unsteady turbulent open-channel flows by means of seeding with hydrogen bubbles

Inverse Problems in Pulse-Echo Ultrasound: Exploiting Coherence for Image Enhancement and Quantitative Imaging

Whereas pulse-echo ultrasound imaging relied on focused acoustic waves since its inception, the last two decades have seen the development of techniques based on unfocused waves, including ultrafast ultrasound imaging. In large part due to the emergence of ...

EPFL2024

Design, computational and experimental investigation of a small-scale turbopump for organic Rankine cycle systems

Jürg Alexander Schiffmann, Sajjad Zakeralhoseini

The hydraulic design, computational analysis, and experimental investigations of a high-speed small-scale turbopump for mobile waste heat recovery applications based on organic Rankine cycle systems are presented in this paper. Such applications demand hig ...

Elsevier2023

Rock-Flow Cell Parameters Evaluation Using Ultrasound Doppler Velocimetry

Giovanni De Cesare, Javier Neves da Silva, Andre Luis Stakowian

This work presents a study of two-phase flow generated inside a rock-flow cell setup. It is characterized by a pipe section filled with fluid (oil in our studies) that is put into oscillation around its mass centre by an electric motor. This type of appara ...

2023

Broadband Air-Coupled Ultrasound Emitter and Receiver Enable Simultaneous Measurement of Thickness and Speed of Sound in Solids

Janez Rus

Air-coupled ultrasound sensors have advantages over contact ultrasound sensors when a sample should not become contaminated or influenced by the couplant or the measurement has to be a fast and automated inline process. Thereby, air-coupled transducers mus ...

MDPI2023

On the Capability of Wall-Modeled Large Eddy Simulations to Predict Particle Dispersion in Complex Turbulent Flows

Mohamed Aly Hashem Mohamed Sayed

Predicting particle transport in turbulent flows has a plethora of applications, some of which are: the transport of atmospheric aerosols, the deposition of blood cells in the arteries of human bodies and the atomization of fuel droplets in combustion cham ...

EPFL2022

Effects of velocity-dependent apparent toughness on the pre- and post-shut-in growth of a hydraulic fracture

Dong Liu, Guanyi Lu

We investigate the growth of a plane-strain/radial hydraulic fracture in an infinite impermeable medium driven by a constant injection rate assuming that the apparent toughness scales with the decreasing fracture growth rate in a power-law relation. The vi ...

ELSEVIER SCI LTD2022

Structure-preserving approaches and data-driven closure modeling for model order reduction

Nicolò Ripamonti

In this thesis, we propose model order reduction techniques for high-dimensional PDEs that preserve structures of the original problems and develop a closure modeling framework leveraging the Mori-Zwanzig formalism and recurrent neural networks. Since high ...

EPFL2022

Measurement of the inner structure of turbidity currents by ultrasound velocity profiling

Giovanni De Cesare, Shun Nomura, Jumpei Hitomi

The inner velocity structure and particle concentration profile of opaque turbidity currents were mea- sured simultaneously by ultrasound velocity profilers. Currents consisting of a quartz particle suspension were generated by using the lock-exchange meth ...

2021

Ultrasonic Doppler flow velocity measurements as a co-indicator for the eco-morphological assessment in a residual flow reach

Giovanni De Cesare, Christian Mörtl, Robin Schroff

It is a complex task to evaluate the effects of a river rehabilitation measure on the riverscape’s habitat mosaic. This study investigated the medium term effects of a rehabilitation measure in a residual flow reach downstream of a hydroelectric dam. The r ...

ETH2021

Data-Driven Reduced-Order Modeling of Convective Heat Transfer in Porous Media

Carlo Fiorina

This work presents a data-driven Reduced-Order Model (ROM) for parametric convective heat transfer problems in porous media. The intrusive Proper Orthogonal Decomposition aided Reduced-Basis (POD-RB) technique is employed to reduce the porous medium formul ...

MDPI2021

Automated flow control of a multi-lane swimming chamber for small fishes indicates species-specific sensitivity to experimental protocols

In fishes, swimming performance is considered an important metric to measure fitness, dispersal and migratory abilities. The swimming performance of individual larval fishes is often integrated into models to make inferences on how environmental parameters ...

2021

The Impact of Surfactants on the Inertial Separation of Bubbles in Microfluidic Electrolyzers

Demetri Psaltis, Seyyed Mohammad Hosseini Hashemi, Pooria Hadikhani

Improving the throughput of electrochemical reactions such as water electrolysis is an ongoing effort. In a membrane-less electrolyzer, product separation can be achieved via controlled two-phase flows within the electrochemical flow cells. In this case, i ...

ELECTROCHEMICAL SOC INC2020

Modeling turbulent stream flows over rough permeable beds

Christophe Ancey, Gauthier Paul Daniel Marie Rousseau, Ivan Pascal

In steep streams, turbulent flows run over coarse sediments that are similar in size to flow depth. Under these conditions, a significant part of the flow may seep through the permeable bed. Based on experimental data, this paper presents a model able to r ...

CRC Press2020

Deformation of porous flexible strip in low and moderate Reynolds number flows

François Gallaire, Pedro Miguel Nunes Pereira de Almeida Reis, Matteo Pezzulla

We present results from a combined experimental and numerical investigation of the fluid-structure interaction of cantilevered porous flexible strips, towed through a fluid bath. We characterize the steady-state deformation of the strips and their associat ...

AMER PHYSICAL SOC2020

Turbulent Flows over Rough Permeable Beds in Mountain Rivers: Experimental Insights and Modeling

Gauthier Paul Daniel Marie Rousseau

Steep mountain streams exhibit shallow waters with roughness elements such as stones and pebbles that are comparable in size to flow depth. Owing to the difficulty in measuring fluid velocities at the interface, i.e., from the rough permeable bed to the fr ...

EPFL2019

Numerical analysis for detecting head losses in trifurcations of high head in hydropower plants

François Avellan, Ramiro Gustavo Ramirez Camacho

Many different types of branching have been developed, such as bifurcation, trifurcation, and manifolds, among others. These configurations are used in penstocks to transport water from surge tanks to power houses in order to feed several turbines at the s ...

Pergamon-Elsevier Science Ltd2019

GPU-accelerated Pelton turbine simulation using finite volume particle method coupled with linear eddy viscosity models

François Avellan, Ebrahim Jahanbakhsh, Sebastián Camilo Leguizamón Sarmiento, Siamak Alimirzazadeh, Audrey Paulette Solange Maertens, Takashi Kumashiro

The numerical investigation of the unsteady flow patterns around a Pelton bucket can be helpful to improve the overall turbine efficiency by optimizing the bucket design based on identified loss mechanisms. Since the flow is highly turbulent, modeling the ...

IOP PUBLISHING LTD2019

Continuously-fed gravity currents propagating over a finite porous substrate

Anton Schleiss, Mário Jorge Rodrigues Pereira Da Franca, Sara Venuleo

We present the results of laboratory investigations of continuously-fed density currents that propagate first over a smooth horizontal bed and then over a porous substrate of limited length. Inflow discharge, initial excess density, and substrate porositie ...

2019

Self-consistent triple decomposition of the turbulent flow over a backward-facing step under finite amplitude harmonic forcing

François Gallaire, Philippe Meliga, Eunok Yim

We investigate the saturation of harmonically forced disturbances in the turbulent flow over a backward-facing step subjected to a finite amplitude forcing. The analysis relies on a triple decomposition of the unsteady flow into mean, coherent and incohere ...

ROYAL SOC2019

Dynamics and Optimal Control of Self-Sustained Instabilities in Laminar and Turbulent Swirling Flows: Application to the Part Load Vortex Rope in Francis Turbines

Simon Pasche

In 2050, the European commission plans to achieve actual energetic transition, which contributes in meeting the climate change challenges by moving away from the fossil fuels and by developing a competitive low-carbon economy. As a consequence, a foreseeab ...

EPFL2018