Marion Erpelding

History independence of steady state in simultaneous two-phase flow through two-dimensional porous media.

It is well known that the transient behavior during drainage or imbibition in multiphase flow in porous media strongly depends on the history and initial condition of the system. However, when the steady-state regime is reached and both drainage and imbibition take place at the pore level, the influence of the evolution history and initial preparation is an open question. Here, we present an extensive experimental and numerical work investigating the history dependence of simultaneous steady-state two-phase flow through porous media. Our experimental system consists of a Hele-Shaw cell filled with glass beads which we model numerically by a network of disordered pores transporting two immiscible fluids. From measurements of global pressure evolution, histograms of saturation, and cluster-size distributions, we find that when both phases are flowing through the porous medium, the steady state does not depend on the initial preparation of the system or on the way it has been reached.

Film flow dominated simultaneous flow of two viscous incompressible fluids through a porous medium

We present an experimental study of two-phase flow in a quasi-two-dimensional porous medium. The two phases, a water-glycerol solution and a commercial food grade rapeseed/canola oil, having an oil to water-glycerol viscosity ratio of 1.3, are injected simultaneously into a Hele-Shaw cell with a mono-layer of randomly distributed glass beads. The two liquids are injected into the model from alternating point inlets. Initially, the porous model is filled with the water-glycerol solution. We observe that after an initial transient state, an overall static cluster configuration is obtained. While the oil is found to create a connected system spanning cluster, a large part of the water-glycerol clusters left behind the initial invasion front is observed to remain immobile throughout the rest of the experiment. This could suggest that the water-glycerol flow-dynamics is largely dominated by film flow. The flow pathways are thus given through the dynamics of the initial invasion. This behavior is quite different from that observed in systems with large viscosity differences between the two fluids, and where compressibility plays an important part of the process.

Mechanical response of granular media: New insights from Diffusing-Wave Spectroscopy

We experimentally investigate the deformation of a granular material submitted to a localised compression force. The strain field is characterised using a near field Diffusing-Wave Spectroscopy technique. The results of point load experiments on an elastic sample are first presented to illutrate the possibilities of the technique. Then, we report new results concerning the behaviour of a granular medium, showing a non-linear response with the force increment and a spatial repartition of the strain that differs from elasticity. Moreover, we analyse the partial reversibility of the deformation after a loading/unloading cycle in terms of both elastic and plastic contributions.

Interferometric measurements of small deformations of granular materials

We present an experimental method based on optical interferences to perform spatially resolved measurements of inhomogeneous deformations in range 10−6–10−4 of solid materials. In particular, we show that the method can be used to measure inhomogeneous deformation fields in granular materials, with a spatial resolution of a few beads diameters.