Publications by François Gallaire

Prediction of the hub vortex instability within wind turbine wakes and effects of the incoming wind and turbine aerodynamic characteristics

Fernando Porté Agel, François Gallaire, Giacomo Valerio Iungo, Francesco Viola

Instability of the hub vortex, which is a vorticity structure present in wind turbine near-wake and mainly oriented along the streamwise direction, is predicted from wake velocity measurements. In this work, stability analysis is performed on wind tunnel v ...

2014

Second-order sensitivity of parallel shear flows and optimal spanwise-periodic flow modifications

François Gallaire, Edouard Boujo, Andrea Fani

We perform a second-order sensitivity analysis of the linear temporal stability of a parallel flow subject to small spanwise periodic modification. The need for a second-order analysis results from the fact that spanwise-periodic flow modifications have a ...

2014

Marangoni induced force on a drop in a Hele Shaw cell

François Gallaire, Philippe Meliga

We analyse the force balance on a cylindrical drop in a Hele-Shaw cell, subjected to a Marangoni flow caused by a surface tension gradient. Depth-averaged Stokes equations, called Brinkman equations, are introduced and a general closed form solution is obt ...

American Institute of Physics2014

Prediction of the hub vortex instability in a wind turbine wake: stability analysis with eddy-viscosity models calibrated on wind tunnel data

Fernando Porté Agel, François Gallaire, Giacomo Valerio Iungo, Francesco Viola

The evolution and downwind recovery of wind turbine wakes are crucial factors for the evaluation of waketo-wake interactions within a wind farm and, in turn, for the prediction of wind power harvesting. Wind turbine wakes are affected by the design of wind ...

2014

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 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

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

Forced reattachment in separated flows: a variational approach to recirculation length reduction

François Gallaire, Edouard Boujo

Sensitivity analysis is used to design an open-loop control for separated flows. The length of the recirculation region

l_c

is expressed as a cost functional, and its sensitivity to actuation is derived analytically. This analysis allows to identify regi ...

2013

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

Deformable Droplets, a numerical account

François Gallaire, Mathias Nagel

We simulate confined droplets in microchannels by depth-averaged equations solved by a boundary element method. The retarding effect due to film formation is absent in the depth-averaged approach and added by a nonlinear boundary condition. Although deform ...

2013

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Prediction of the hub vortex instability within wind turbine wakes and effects of the incoming wind and turbine aerodynamic characteristics

Second-order sensitivity of parallel shear flows and optimal spanwise-periodic flow modifications

Marangoni induced force on a drop in a Hele Shaw cell

Prediction of the hub vortex instability in a wind turbine wake: stability analysis with eddy-viscosity models calibrated on wind tunnel data

Open-loop control of a separated boundary layer

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

Open-loop control of noise amplification in separated boundary layers

Forced reattachment in separated flows: a variational approach to recirculation length reduction

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

Deformable Droplets, a numerical account

Second-order sensitivity of parallel shear flows and optimal spanwise-periodic flow modifications

Marangoni induced force on a drop in a Hele Shaw cell

Forced reattachment in separated flows: a variational approach to recirculation length reduction

Prediction of the hub vortex instability in a wind turbine wake: stability analysis with eddy-viscosity models calibrated on wind tunnel data

Open-loop control of a separated boundary layer

Open-loop control of noise amplification in separated boundary layers

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

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

Deformable Droplets, a numerical account

Prediction of the hub vortex instability within wind turbine wakes and effects of the incoming wind and turbine aerodynamic characteristics