Publications related to Chute Aerators : Steep Deflectors and Cavity Subpressure

Laterally unconfined neutral or negative buoyancy inflow into a quiescent ambient over sloping bottom

This work studies the nearshore hydrodynamics of a shallow turbulent flow entering a laterally unconfined quiescent ambient with a sloping bottom boundary. Examples of such flow are neutrally buoyant ebb tidal jets and hyperpycnal river plumes entering ope ...

EPFL2023

Interactions of Cavitation Bubbles with Deformable Interfaces

Armand Baptiste Sieber

Cavitation is a topic that has long been of interest due to the large and growing range of applications associated with it. This is mainly because the collapse of cavitation bubbles releases a considerable amount of energy into the surrounding environment. ...

EPFL2023

Measurement and modelling of dynamic fluid saturation in carbon reinforcements

Véronique Michaud, Baris Çaglar, Helena Luisa Teixido Pedarros, Guillaume Clément Broggi

We propose a methodology to monitor the progressive saturation of a non-translucent unidirectional carbon fabric stack through its thickness by means of X-ray radiography and extract the dynamic saturation curves using image analysis. Four constant flow ra ...

2023

Temporal and spatial evolution of cavitating bubbles and coherent structures in a confined submerged jet shear layer

Sebastián Camilo Leguizamón Sarmiento, Yuchuan Wang

Purpose The study aims to display the bubbles' evolution in the shear layer and their relationship with the pressure fluctuations. Furthermore, the coherent structures of the first six modes are extracted, in order to provide insight into their temporal an ...

EMERALD GROUP PUBLISHING LTD2021

Evaluation of a Dynamic Transfer Matrix for a Hydraulic Turbine

François Avellan, Andres Müller, Keita Yamamoto

It is well known that hydraulic machines experience various types of flow instabilities causing a negative influence on the system under off-design operations. The transfer matrix method correlating the flow properties in upstream and downstream of hydraul ...

2020

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

Mohamed Farhat, Huaiyu Cheng

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 ...

ELSEVIER SCIENCE INC2020

Invariant solutions underlying small- and large-scale structures in turbulent boundary layers

Sajjad Azimi

Flows of gases and liquids interacting with solid objects are often turbulent within a thin boundary layer. As energy dissipation and momentum transfer are dominated by the boundary layer dynamics, many engineering applications can benefit from an improved ...

EPFL2020

Stilling Basin Performance Downstream of Stepped Spillways

Ivan Stojnic

Advances in dam construction techniques have significantly increased the number of implemented stepped spillways worldwide. A key hydraulic feature of a stepped chute, compared to a smooth chute, is the enhanced energy dissipation resulting in a reduced re ...

EPFL2020

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

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

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

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

Turbulent patterns in wall-bounded shear flows: invariant solutions and their bifurcations

Florian Reetz

When laminar shear flows in large wall-bounded domains transition to turbulence, the flow exhibits spatio-temporally chaotic dynamics. Despite its chaotic dynamics, the flow may self-organize into characteristic spatially periodic patterns of unknown origi ...

EPFL2019

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

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

Flow dynamics of a dandelion pappus: A linear stability approach

François Gallaire, Francesco Viola, Lorenzo Siconolfi, Pier Giuseppe Ledda

The study and control of flow instabilities is a key problem in aerodynamics. Aircrafts are designed not only to generate the lift force needed to balance their weight but, more importantly, to be stable and reasonably steady when in cruise conditions. Sim ...

2019

Suppression of von Karman vortex streets past porous rectangular cylinders

François Gallaire, Francesco Viola, Lorenzo Siconolfi, Pier Giuseppe Ledda

Although the stability properties of the wake past impervious bluff bodies have been widely examined in the literature, similar analyses regarding the flow around and through porous ones are still lacking. In this work, the effect of the porosity and perme ...

2018

A model for the effect of pressure gradient on turbulent axisymmetric wakes

Fernando Porté Agel, Sina Shamsoddin

Turbulent axisymmetric wakes under pressure gradient have received little attention in the literature, in spite of their fundamental and practical importance, for example, in the case of wind turbine wakes over topography. In this paper, we develop an anal ...

Cambridge University Press2018

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

A Simple Physically-Based Model for Wind-Turbine Wake Growth in a Turbulent Boundary Layer

Fernando Porté Agel, Wai Chi Cheng

The growth rate of wind-turbine wakes in the atmospheric boundary layer is a key parameter in analytical models used to predict wind-turbine wakes and their effects in wind farms. To date, the turbine-wake growth rate is determined empirically, owing to ou ...

2018