ESPCI web site
Flow of polymer solutions in porous media : rheology, slippage, confinement and turbulence
Polymer solutions are used to control biphasic flows in porous media since by increasing the viscosity they tend to prevent fingering and to smooth the permeability heterogeneities. However, several additional phenomena need to be considered, such as non-linear rheology, elasticity and violation of the no-slip boundary condition at a solid interface. During this talk, I will discuss these issues starting from an approach based on experiments and modelling in well controlled flow geometries made using microfluidics. Biphasic experiments in channel networks lead to the conclusion that, when elastic forces are small (e.g. at low concentration) both shear-thinning and slippage lead to even more pronounced fingering phenomenon. Since slippage dominates the flows at small scales - typically below a few micrometers- , we specifically studied it as a function of the channel size. We developed for that issue a nanofluidic approach which enables us to characterize pressure driven flows thanks to fluorescence photobleaching. The experimental results show that though slippage indeed dominates the flow and leads to a decrease of the effective viscosity of the polymer solutions, this reduction is much less than expected, meaning that slippage is reduced in confined flows. I will finish with some recent results concerning the crucial role of elastic turbulence at higher concentrations.