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François Gallaire

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Publications associées (155)

Open-loop control of a separated boundary layer

François Gallaire, Edouard Boujo

Linear optimal gains

G_opt(\omega)

are computed for the separated boundary-layer flow past a two-dimensional bump in the subcritical regime. Very large values are found, making it possible for small-amplitude noise to be strongly amplified and to destabi ...

Cépaduès Editions2013

A unified criterion for the centrifugal instabilities of vortices and swirling jets

François Gallaire

Swirling jets and vortices can both be unstable to the centrifugal instability but with a different wavenumber selection: the most unstable perturbations for swirling jets in inviscid fluids have an infinite azimuthal wavenumber, whereas, for vortices, the ...

Cambridge University Press2013

Generic path for droplet relaxation in microfluidic channels

François Gallaire, Mathias Nagel, Pierre-Thomas Paul Brun

In two-phase microfluidics, droplets often undergo deformations that drive them away from their circular equilibrium shape. Herein we concentrate on the relaxation of symmetrical deformations to a circle driven by surface tension effects, which are predomi ...

American Physical Society2013

Open-loop control of noise amplification in separated boundary layers

François Gallaire, Edouard Boujo

Linear optimal gains are computed for the subcritical two-dimensional separated boundary-layer flow past a bump. Very large optimal gain values are found, making it possible for small-amplitude noise to be strongly amplified and to destabilize the flow. Th ...

2013

A new prediction of wavelength selection in radial viscous fingering involving normal and tangential stresses

François Gallaire, Mathias Nagel

We reconsider the radial Saffman-Taylor instability when a fluid injected from a point source displaces another fluid of higher viscosity in a Hele-Shaw cell where the fluids are confined between two neighboring flat plates. The advancing fluid front is un ...

2013

Interface-induced recirculation within a stationary microfluidic drop

François Gallaire

We study the flow within a stationary drop in a Hele-Shaw cell. The experiments are performed in a microfluidic channel, whose surface is patterned with a single hole that serves to anchor the drop while the outer fluid continues to flow. The recirculation ...

Royal Society of Chemistry2012

A weakly nonlinear mechanism for mode selection in swirling jets

François Gallaire, Philippe Meliga

Global linear and nonlinear bifurcation analysis is used to revisit the spiral vortex breakdown of nominally axisymmetric swirling jets. For the parameters considered herein, stability analyses single out two unstable linear modes of azimuthal wavenumber m ...

Cambridge University Press2012

Counterpropagating Rossby waves in confined plane wakes

François Gallaire, Luca Biancofiore

In the present work, we revisit the temporal and the spatio-temporal stability of confined plane wakes under the perspective of the counterpropagating Rossby waves (CRWs). Within the context of broken line velocity profiles, each vorticity discontinuity ca ...

American Institute of Physics2012

Numerical pancake droplets: from capturing to versatile microfluidics

François Gallaire, Mathias Nagel

This article proposes a numerical model for microfluidic two-phase flows in flat channels, also called Hele-Shaw cells. The initially three-dimensional problem is simplified to two-dimensions by depth averaging in the thin direction. The 2D partial differe ...

SOCIETE HYDROTECHNIQUE DE FRANCE2012

New prediction for wave length selection of radial fingering in a Hele-Shaw cell

François Gallaire, Mathias Nagel

Existing linear stability analysis of radial fingering in Hele-Shaw cells use Darcy’s law as a model for the fluid motion. Comparison between experiments and theory reveals a large discrepancy at order 1 capillary numbers. In this work we use the so-called ...

Association Française De Mécanique2011

Etude expérimentale de l’écoulement derrière une bosse

François Gallaire, Edouard Boujo

Properties of the unsteady separated flow over a bump mounted on a flat plate are studied experimen- tally, with the aim of characterizing the instabilities of this flow and developing a control strategy. Results from measurements using particle image velo ...

Association Française De Mécanique2011

Quantitative analysis of the dripping and jetting regimes in co-flowing capillary jets

François Gallaire

We study a liquid jet that breaks up into drops in an external co-flowing liquid inside a confining microfluidic geometry. The jet breakup can occur right after the nozzle in a phenomenon named dripping or through the generation of a liquid jet that breaks ...

2011

Influence of confinement on a two-dimensional wake

François Gallaire, Luca Biancofiore

The spatio-temporal development of an incompressible two-dimensional viscous wake flow confined by two flat slipping plates is investigated by means of direct numerical simulation (DNS), using a spectral Chebyshev multi-domain method. The limit between uns ...

Cambridge University Press2011

The influence of shear layer thickness on the stability of confined two-dimensional wakes

François Gallaire, Luca Biancofiore

The influence of confinement onto the inviscid and incompressible linear stability of the family of wakes introduced by Monkewitz [Phys. Fluids 31, 999 (1988)] is examined. The nondimensional parameters of the model, the velocity ratio Λ, defined as ratio ...

2011

Control of axisymmetric vortex breakdown in a constricted pipe: Nonlinear steady states and weakly nonlinear asymptotic expansions

François Gallaire, Philippe Meliga

The present paper investigates numerically and theoretically the axisymmetric vortex breakdown occurring in a constricted pipe of infinite extension, i.e., the transition from a smooth columnar state to a breakdown state exhibiting a recirculation bubble. ...

2011

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