Modeling of contaminants mobility in underground domains with multiple free/porous interfaces

Abstract

[1] Existing simulation techniques for subsurface water quality management remain inadequate despite the phenomenal progress made in the computing capabilities in the past 2 decades. One major lacunas found in mathematical models for groundwater hydrodynamics in combined free flow zones (zones that are devoid of porous materials) and porous domains (e.g., soil water regions) in the subsurface is that these models impose continuity of all flow/transport parameters to describe the flow behavior at the intermediate surfaces between the two zones. Prescription of such interfacial conditions cannot always be physically justified and, in general, result in ill-posed mathematical formulations. The present paper aims to remove the above limitations of the mathematical models by imposing well-posed mathematical formulations of mass and momentum transfer across the boundaries between free and porous zones underground for simulating subsurface flow. The possibility of the existence of a multiple number of pervious boundaries in the domain across which water may flow is considered in this work, as it represents the most realistic scenario for the subsurface transport processes. The hydrodynamics of coupled fluid flow and behavior of contaminants transport are described. Combined effects of Darcy and Reynolds numbers on the subsurface transport of contaminants are discussed. Sensitivity of the flow variables to a coefficient of the permeability and porosity of interfacial boundary, which is determined by its structural properties, is also considered.

Inertial effects in dispersion in porous media

“…In groundwater systems, dispersion in inertial flows have been identified as important for contaminant transport in porous media in the hyporheic zone [ Prinos et al , 2003; Cardenas and Wilson , 2006; Wagner and Bretschko , 2002], subsurface contaminant remediation under high‐velocity flows [ Das and Nassehi , 2003], and flow through fractured rock [ Ivars , 2006]. In an early study compiling the known information regarding dispersion [ Pfannkuch , 1963] identified an inertial regime, and presented data indicating that fluid flow in this regime influenced the longitudinal dispersion coefficient.…”

Three‐dimensional finite element modelling of coupled free/porous flows: applications to industrial and environmental flows

“…In the interior region, a no‐slip boundary condition is imposed on the inner face of the impermeable barrier. The porous medium is considered to be saturated, anisotropic and homogeneous with the permeability values selected as K xx = 3.36 × 10 − 10 , K yy = 2.37 × 10 − 10 and K zz = 1.48 × 10 − 10 m 2 , which are based on the work of Das and Nassehi .…”

“…Reactive barriers constitute an emerging technology for in situ remediation of groundwater contamination and have many advantages over the traditional ex situ treatment methods. The transport domains during groundwater flow through reactive barriers often may involve free‐flow or non‐porous sections . To model the fluid mobility efficiently in such situations, the free and porous flow zones (permeable reactive barriers) must be studied in conjunction with each other.…”

Assessment of groundwater contamination risk by BTEX from residual fuel soil phase

“…When the upward movement of the water level occurs, part of the NALP follows the rise of the water table, and another part is trapped below it, due to a capillary hysteresis that reduces its mobility. In the opposite direction, when the water level drops, the water drains from the porous medium and the NALP agglutinate, increasing their saturation and mobility [19][20][21][22][23]. However, NALP presence as an independent phase was not fixed in the model, so groundwater level was considered steady.…”