GALLAIRE , François

A separated boundary layer flow at the rear of a bump is considered. Two-dimensional equilibrium stationary states of the Navier-Stokes equations are determined using a nonlinear continuation procedure varying the bump height as well as the Reynolds number. A global instability analysis of the steady states is performed by computing...

We prove the nonlinear stability of boundary layer profiles of the incompressible Navier-Stokes equation under a spectral assumption on the linearized operator. The main result applies for example to the classical Blasius layer

Large-eddy simulations (LESs) of obstacle-free wakes, in a channel like geometry with an homogeneous transverse direction, are carried out in order to investigate the influence of confinement on turbulent wakes. The numerical solver makes use of a multi-domain Fourier–Chebyshev spectral method and the LES capability is implemented through a...

Large-eddy simulations (LESs) of obstacle-free wakes, in a channel like geometry with an homogeneous transverse direction, are carried out in order to investigate the influence of confinement on turbulent wakes. The numerical solver makes use of a multi-domain Fourier–Chebyshev spectral method and the LES capability is implemented through a...

The direct numerical simulation of the incompressible Navier-Stokes equations of the flow above a bump shows a stationary longitudinal instability at a Reynolds number of Re=400. A three-dimensional global mode linear analysis is used to interpret these results and shows that the most unstable eigenmode is steady and localized in the...

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 unstable and stable configurations is determined with respect to several non-dimensional...

We study experimentally a system composed of an elastic membrane in which water is periodically flushed from a heart-like pump. Our first interest is the occurrence of waves as opposed to an homogeneous mode of deformation of our membrane. These modes may explain differences in the localization of aneurysms in the body. Then we show the case of...

We study experimentally a system composed of an elastic membrane in which water is periodically flushed from a heart-like pump. Our first interest is the occurrence of waves as opposed to an homogeneous mode of deformation of our membrane. These modes may explain differences in the localization of aneurysms in the body. Then we show the case of...

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 unstable and stable configurations is determined with respect to several non-dimensional...

International audience

We study the stability of two-dimensional solutions of the three-dimensional Navier-Stokes equations, in the limit of small viscosity. We are interested in steady flows with locally closed streamlines. We consider the so-called elliptic and centrifugal instabilities, which correspond to the continuous spectrum of the underlying linearized Euler...

It was recently demonstrated by our group that a focused laser beam could be used to produce a net force on a moving microfluidic drop. The aim of the paper is to establish a scaling law for this net force by a examining the closely related but simpler situation of a very thin stationary circular drop of fixed shape submitted to a...

Tammisola et al (2012 J. Fluid Mech. 713 632-58) have observed a counter-intuitive destabilizing effect of the surface tension in planar wakes by means of a global linear analysis. In the present study, we conduct direct numerical simulation (DNS) of wakes of two immiscible fluids. The numerical scheme is based on a level set approach to track...

A popular method to induce synthetic propulsion at the microscale is to use the forces created by surface-produced gas bubbles inside the asymmetric body of a catalytic swimmer (referred to in the literature as microrocket). Gas bubbles nucleate and grow within the catalytic swimmer and migrate toward one of its opening under the effect of...

The localized heating produced by a tightly focused infrared laser leads to surface tension gradients at the interface of microfluidic drops covered with surfactants, resulting in a net force on the drop whose origin and magnitude are the focus of this paper. First, by colocalization of the surfactant micelles with a fluorescent dye, we...

The temperature increase of a thin water layer is investigated, both experimentally and numerically, when the layer is heated by an infrared laser. The laser is focused to a waist of 5.3 µm inside a 28 µm gap that contains fluorescent aqueous solutions between two glass slides. Temperature fields are measured using the temperature sensitivity...

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Droplets are natural candidates for use as microfluidic reactors, if active control of their formation and transport can be achieved. We show here that localized heating from a laser can block the motion of a water-oil interface, acting as a microfluidic valve for two-phase flows. A theoretical model is developed to explain the forces acting on...

The stability of the two-dimensional flat plate boundary-layer is studied by means of global eigenmodes. These eigenmodes depend both on the streamwise and wall-normal coordinate, hence there are no assumptions on the streamwise length scales of the disturbances. Expanding the perturbation velocity field in the basis of eigenmodes yields a...