This study assesses the ability of a sensitivity-based, span-wise homogeneous control velocity distributed at the surface of a circular cylinder to cut down the cost of reducing drag by more classical techniques, e.g., base bleed and lateral suction. At Re ...

ELSEVIER SCIENCE BV2018

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

Onset of chaos in helical vortex breakdown at low Reynolds number

François Avellan, Simon Pasche, François Gallaire

2018

Viscous Taylor droplets in axisymmetric and planar tubes: from Bretherton’s theory to empirical models

Gioele Mariano Nicolò Balestra, François Gallaire, Lailai Zhu

The aim of this study is to derive accurate models for quantities characterizing the dynamics of droplets of non-vanishing viscosity in capillaries. In particular, we propose models for the uniform-film thickness separating the droplet from the tube walls, ...

2018

Theoretical framework to analyze the combined effect of surface tension and viscosity on the damping rate of sloshing waves

François Gallaire, Francesco Viola

Gravity force, surface tension, oscillating boundary layers, viscous dissipation, static meniscus, contact angle hysteresis, and moving contact lines are typical features of sloshing dynamics. All these ingredients influence capillary-gravity waves in a co ...

AMER PHYSICAL SOC2018

Bifurcation Dynamics of a Particle-Encapsulating Droplet in Shear Flow

François Gallaire, Lailai Zhu

To understand the behavior of composite fluid particles such as nucleated cells and double emulsions in flow, we study a finite-size particle encapsulated in a deforming droplet under shear flow as a model system. In addition to its concentric particle-dro ...

American Physical Society2017

Flow control of weakly non-parallel flows: application to trailing vortices

François Gallaire, Giacomo Valerio Iungo, Francesco Viola, Erica Pezzica

A general formulation is proposed to control the integral amplification factor of harmonic disturbances in weakly non-parallel amplifier flows. The sensitivity of the local spatial stability spectrum to a base-flow modification is first determined, general ...

Cambridge University Press2017

Swimming with a cage: low-Reynolds-number locomotion inside a droplet

François Gallaire, Lailai Zhu

Inspired by recent experiments using synthetic microswimmers to manipulate droplets, we investigate the low-Reynolds-number locomotion of a model swimmer (a spherical squirmer) encapsulated inside a droplet of a comparable size in another viscous fluid. Me ...

Royal Society of Chemistry2017

Dynamics of falling films on the outside of a vertical rotating cylinder: waves, rivulets and dripping transitions

François Gallaire, Nicolas Igor Jacques Kofman

Falling liquid films on the underside of a plate or on the outside of a rotating cylinder are subject to a destabilizing body force. The evolution of the film topology is determined by interactions between the Kapitza and the Rayleigh-Taylor instability, l ...

Cambridge University Press2017

Understanding the destabilizing role for surface tension in planar shear flows in terms of wave interaction

François Gallaire, Luca Biancofiore

Both surface tension and buoyancy force in stable stratification act to restore perturbed interfaces back to their initial positions. Hence, both are intuitively considered as stabilizing agents. Nevertheless, the Taylor-Caulfield instability is a countere ...

Amer Physical Soc2017

The viscous torsional pendulum

François Gallaire, Francesco Viola

A disk that is free to rotate about its axis and connected to a torsional spring behaves as a damped oscillator when twisted and released. The initial elastic energy is periodically turned to kinetic energy and it gets progressively dissipated by the visco ...

Academic Press Ltd- Elsevier Science Ltd2017

Ultralow Interfacial Tension Measurement through Jetting/Dripping Transition

Laura Augello, François Gallaire

In this paper, we present a dynamic microfluidic tensiometer able to perform measurements over more than four decades and which is suitable for high throughput experimentations. This tensiometer is able to withstand hard conditions such as high pressure, h ...

American Chemical Society2017

Sloshing in a Hele-Shaw cell: experiments and theory

François Gallaire, Francesco Viola, Benjamin Jérémy Dollet

The response of the free liquid surface in a Hele-Shaw cell subjected to a horizontal oscillation is investigated. We study the low-oscillation-amplitude regime and we show, by varying the fluid viscosity, nu, and the forcing frequency, omega, that the rat ...

Cambridge University Press2017

Numerical simulation and sensitivity analysis of a low-Reynolds-number flow around a square cylinder controlled using plasma actuators

François Gallaire, Philippe Meliga, Edouard Boujo

Flow around a square cylinder controlled using plasma actuators (PAs) is numerically investigated by direct numerical simulation in order to clarify the most effective location of actuator installation and to elucidate the mechanism of control effect. The ...

Amer Physical Soc2017

Fluid dynamic instabilities: theory and application to pattern forming in complex media

François Gallaire, Pierre-Thomas Paul Brun

In this review article, we exemplify the use of stability analysis tools to rationalize pattern formation in complex media. Specifically, we focus on fluid flows, and show how the destabilization of their interface sets the blueprint of the patterns they e ...

Royal Society, The2017

Part Load Vortex Rope as a Global Unstable Mode

François Avellan, Simon Pasche, François Gallaire

Renewable energy sources (RES) have reached 23.7% of the worldwide electrical generation production in 2015. The hydraulic energy contribution amounts to 16.6% and comes mainly form large-scale hydropower plants, where Francis turbines represents 60% of th ...

American Society of Mechanical Engineers2017

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