Polymer solutions in porous media : insights from microfluidics.
par- 9 mars 2015
Lieu du séminaire : Salle de réunion Bâtiment André Rassat (Bat E)
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 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 both shear-thinning and slippage lead to even more pronounced fingering phenomenon. For dilute solutions, slippage dominates the flows at small scales - typically below a few micrometers- , we specifically studied it as a function of the channel size. 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. At higher concentrations, elastic forces offers the unique opportunity to trigger turbulence at small scales. Recent experimental results in straight channels and in micromodels lead to the conclusion that elastic turbulence greatly homogenize the flow.
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