Movement of bacteria in a porous medium
We study the transport of E-coli bacteria in a microfluidic cell (height 100 mu / width 500 mu)
containing obstacles (white circles).
The colored lines show the trajectories of the bacteria transported by a fluid flowing
at 70 microns / second.
The insert illustrates the fluid-bacteria coupling:
we see a bacteria (yellow line) that flows along the surface of grains and moves upstream.
Crack patterns in paintings
The large variety of craquelures reveal some characteristics of the pictorial layer. Moreover studying the stability of a crack network is essential in the domain of heritage conservation. The formation of a crack network is investigated using model systems in a multi-layered geometry.
Chemical wave fronts in disordered flow
Interface motion are relevant to a wide variety of dynamical processes including population dynamics in biology, chemical reaction, solidification, flame propagation in combustion and marine ecology systems. We investigate the coupling between reaction fronts and disordered flow through a model porous medium. The front is generated by a reaction between two chemical species which produces Fisher waves. These reaction fronts propagate as solitary waves with a constant velocity and a stationary concentration profile. We study the dynamics and morphology of these fronts resulting from the interaction between the flow and the sustained reaction.
Viscous fingering and flow of active fluid
The situation where one fluid is displaced by a second one is a basic situation found in many applications.
Our investigation focusses on the possible flow changes arising when one of the fluid is active. This is achieved here by using suspensions of various strains of motile bacteria injected in Hele Shaw cell.
Yield stress fluid flow in porous media
The non-Newtonian fluids intervene in numerous industrial processes.
The flow of yield stress fluids, viz. that require a minimal shear stress for flowing, is investigated in different heterogenous media (porous media, factures...).
The presence of heterogeneities induces many different flowing regimes that we aim to characterize.
Adhesion of soft polymers
In the framework of the ANR project AdhesiPS (2018-2022), we study experimentally the adhesion of
soft polymers on patterned substrates: the links between the level of adhesion and the large-strain rheology
of the glue as well as the dynamical and spatial instabilities that emerge in certain ranges of velocities during peeling experiments.
We use microtextured substrates as a tool to explore the fundamental mechanisms of energy dissipation
as well as a possible means of controlling the adhesion force.
Stability of a coating submitted to cycling mechanical stresses
How does a crack network evolve under the effect of a cycling mechanical stress? We consider the case of a nanospring coating.
A cylindrical rod (bottom center) floats in an upward flow between two parallel glass rectangular plates parallel to the plane of the figure. It displays here a swinging motion with a periodic oscillation of its angle with respect to the horizontal: this motion has been visualized by injecting two parallel streaks of dye reaching the cylinder near its ends (the false colors correspond to the concentration of dye). The trajectory of the dye demonstrates a possible mixing mechanism associated to this instability.