MixUQ · Quantification of mixing and dynamic uncertainty for transport in heterogeneous porous media
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2020-12-01 → 2023-02-28
- EU contribution
- €160,932
- Participants
- 1
- Scheme
- MSCA-IF
Lines connect the coordinator with its partners.
Results in brief
Quantification of mixing and dynamic uncertainty for transport in heterogeneous porous media
Heterogeneity in geological media spans several spatial scales, ranging from the complex arrangement of different geo-materials at the kilometer scale to the intricacy of the pore architectures below the millimeter scale. At the aquifer scale, heterogeneity in the hydraulic conductivity is the dominant factor. The latter underpins the complex spatial organization of the flow field whose spatial fluctuations drive the transport of dissolved chemicals in the subsurface. In this context, spreading is a measure of the extension of a contaminant plume, while mixing refers to the degree of contaminant dilution. In heterogeneous formations, the prediction of plume spread is not sufficient to characterize mixing, because sub-plume-scale fluctuations in the concentration field are not negligible, i.e., mixing is incomplete (see figure). Furthermore, the hidden nature of the subsurface leads to uncertainty about the exact heterogeneous arrangement of the hydraulic conductivity of the aquifer. The latter must be projected onto the fate of solute to address central societal issues associated with the management of groundwater resources and risk assessment analysis. The MixUQ project proposed a new way to reconcile the spreading and mixing dynamics of a solute plume transported within a heterogeneous aquifer (under incomplete mixing), while allowing the uncertainty quantification of its mixing state.
Data: CORDIS, © European Union
Project objective
Natural and engineered porous systems exhibit heterogeneity across several spatial scales leading to complex flow fields with strong fluctuations. The latter enhance the segregation and distortion of a transported scalar mixture, while diffusion promotes the local homogenization of it. In this context, spreading has been traditionally identified with the overall growth of the dissolved plume while mixing with the internal plume homogenization. Accurate quantification of mixing in heterogeneous media is one of the most relevant and still open challenges. Our current failure lay in the inability of capturing the interplay between flow fluctuations and local diffusion: the former promotes both the internal plume segregation (at early times, dominance of pure advection) and the subsequent homogenization (at late times; dominance of dispersion) by the sampling of flow fluctuations which trigger the internal folding and distortion of the plume enabling local homogenization by diffusion (coalescence mechanism). We here propose to predict mixing within a unified framework (Work package 1) which leverage on the Lamellar description of transport and capture the early (segregation) and late (coalescence) time impact of fluctuations by viewing spreading as a sub-plume scale process: the dispersion and interactions of Lamellae are captured through a continuous time random walk (CTRW) approach. At the same time, uncertainty about concentration distribution is a dynamic quantity ruled by the same physical mechanisms: plume segregation (uncertainty production) and homogenization (uncertainty reduction). We here take advantage of the insight from the novel transport model to close evolution equations (e.g., for the variance and the probability density function) apt to describe the dynamic uncertainty (Work package 2). We then explore the establishment of ergodicity for mixing under a variety of conditions (e.g., degree of heterogeneity, strength of diffusion and advection)
Original text from CORDIS.
Participants
- AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS · MadridCoordinatorSpain
Links
Data: CORDIS, © European Union