14-17 May 2018
New Orleans
US/Central timezone

Solute dispersion for stable density-driven flow in randomly heterogeneous porous media

14 May 2018, 16:15
15m
New Orleans

New Orleans

Poster MS 1.16: Heterogeneity, uncertainty, and multiple scales in groundwater problems Poster 1

Speakers

Ms Monica Riva (Dipartimento di Ingegneria Civile e Ambientale, Politecnico di Milano)Mr Alberto Gudagnini (Dipartimento di Ingegneria Civile e Ambientale, Politecnico di Milano)

Description

We present a theoretical investigation on the processes underpinning the reduced longitudinal spreading documented in stable variable density flows, as opposed to constant density settings, within heterogeneous porous media. We do so by decomposing velocity and pressure in terms of stationary and dynamic components. The former corresponds to the solution of the constant density flow problem, while the latter accounts for the effects induced by density variability. We focus on a stable flow configuration and analyze the longitudinal spread of saltwater injected from the bottom of a column formed by a heterogeneous porous medium initially fully saturated by freshwater. We adopt a perturbation expansion approach and derive the equations satisfied by section-averaged concentrations and their ensemble mean values. These formulations are respectively characterized by a single realization and an ensemble dispersive flux, which we determine through appropriate closure equations. The latter are solved via semi-analytical and numerical approaches. Our formulations and associated results enable us to discriminate the relative impact on the density-driven solute displacement of (a) covariance of the permeability of the porous medium, (b) cross-covariance between permeability and concentration, which is in turn linked to the coupling of flow and transport problems, and (c) cross-covariance between the dynamic and stationary velocities.

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Primary authors

Mr Aronne Dell'Oca (1Dipartimento di Ingegneria Civile e Ambientale, Politecnico di Milano) Ms Monica Riva (Dipartimento di Ingegneria Civile e Ambientale, Politecnico di Milano) Mr Jesus Carrera (GHS UPC-CSIC, IDAEA, CSIC) Mr Alberto Gudagnini (Dipartimento di Ingegneria Civile e Ambientale, Politecnico di Milano)

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