Séminaire régulier IUSTI – 14 déc. 2018 – 11h salle 250

Stretching and folding dynamics of material lines in porous flow through granular media

Joris Heyman – OSUR, Rennes

In this talk, I will present recent experimental and numerical results about the stirring potential of flows through porous media. While these flows are observed in many natural contexts (96% of the fresh water resource is underground), their dispersive and reactive properties are only partially understood. As an example, there is no analytical relationship existing between macroscopic scalar dispersion coefficient and Péclet number in such type of flow. Reactive mixing modelling is thus limited to empirical fits that do not reflect pore scale processes. By studying experimentally and numerically the stretching and folding sequence of a solute at pore scale, we found that creeping flow through porous media naturally tends to produce Lagrangian chaos, with an efficiency comparable to most turbulent flows and well-designed mixers.