funding organization: DFG, funding period: 2022-2025

researcher on the project: Marie-Madeleine Stettler

Solutes that are transported in groundwater through heterogeneous porous media are affected by two dispersive processes: diffusive mixing and advective spreading. The former is random and leads to dilution of a plume, which fosters mixing-limited chemical reactions. The latter is deterministically caused by variability in the velocity field at all scales and leads to a volume-preserving distortion of the plume. Because the two processes act simultaneously and interdependently, when transport is induced in exactly opposite directions for the same duration, dispersion as a whole becomes partially reversible. The stronger diffusion is in comparison to advection, the less reversible dispersion becomes, because diffusion destroys the memory of the transport process. We quantify the reversibility of dispersion and investigate how it is influenced by different geostatistical and transport properties. We address this research topic by a variety of methods: Numerical simulations and perturbation theory (see Stettler et al. 2023), as well as statistical and experimental studies.

This research is of interest because it deepens the understanding of mixing in push-pull flow fields and possibly gives insight into how to isolate the individual contributions of mixing and spreading to overall dispersion.

References

M.-M. Stettler, M. Dentz, O.A. Cirpka: Linear stochastic analysis of the partial reversibility of ensemble and effective dispersion in heterogeneous porous media. Water Resour. Res. 59(1): e2022WR033570, 2023, doi: 10.1029/2022WR033570.

O.A. Cirpka, M.-M. Stettler, M. Dentz: Spatial Markov Model for the prediction of travel-time-based solute dispersion in three-dimensional heterogeneous media. Water Resour. Res. 58(6): e2022WR032215, 2022, doi: 10.1029/2022WR032215.