Helical Flow and Transient Solute Dilution in Porous Media

Abstract

Artículo de publicación ISIHelical flow can occur in porous media if the hydraulic conductivity tensor is anisotropic.We study the structure of steady-state flowfields in three-dimensional anisotropic porous media formed by two homogeneous layers, one of which is anisotropic.We simulate transient transport of a conservative scalar in such flowfields by a hybrid streamline/smoothed particle hydrodynamics method and analyze dilution. We use stretching and folding metrics to characterize the flow field and the dilution index of a conservative scalar divided by the volume of the domain to quantify plume dilution. Based on the results of detailed numerical simulations, we conclude that nonlinear deformation triggers dilution and that plume dilution is controlled by two parameters: the contrast between the principal directions of the anisotropic layer, and the orientation of the hydraulic conductivity tensor with respect to the main flow direction. Furthermore, we show that in this kind of flow fields transverse dispersion is responsible for an increase in plume dilution, while the effect of longitudinal dispersion is negligible.DFG (Deutsche Forschungsgemeinschaft) CI-26/11 - 1 Conicyt Chile through Fondecyt Project 11110228 Fondap Project 1509001

Temporal Mixing Behavior of Conservative Solute Transport through 2D Self-Affine Fractures

“…Since the mixing behavior is highly dependent on the flow field [8,9,16,45], the flow field in a single rough fracture was solved directly by using the Navier-Stokes and continuity equations for isothermal, incompressible, and homogenous single Newtonian steady flow:…”

“…This indicates that the spatial distribution of local apertures and the corresponding spatial changes in velocity have a significant influence on the temporal evolution of the SDR. Since mixing is the only process of solute mass exchange between the different streamlines, the distribution of streamlines significantly impacts the mixing [8]. In the constant-aperture fracture, the streamlines are uniform over the entire fracture, whereas the streamlines in the variable-aperture fracture are deformed and bent due to the spatial distribution of local apertures (see Figure 4).…”

“…Characterizing the spreading and mixing processes of conservative solute through the fractures is very important for the understanding of reaction rates and mass transport rates associated with nuclear waste disposal, enhanced oil recovery, and bioremediation [1][2][3][4][5][6]. Although, in recent decades, many studies have provided new insights into the mechanisms and properties of mixing processes in homogeneous and heterogeneous porous media [7][8][9][10][11][12][13][14][15][16][17], to date, little attention has been focused on mixing behavior in fractures.…”

Effects of Cemented Porous Media on Temporal Mixing Behavior of Conservative Solute Transport

“…For the heterogeneous system, the flow velocity distribution in the porous media is a fundamental issue for understanding the mixing behavior of solute plume [21]. As the mixing process is highly influenced by the flow field [22,23], molecular diffusion causes the solute molecule movement between streamlines and enhances mixing. Some recent studies characterized topological [24] and kinematic [25] features of the flow field to explore the influence of the flow field on the mixing behavior of the solute plume.…”

Effect of Anisotropy Structure on Plume Entropy and Reactive Mixing in Helical Flows

“…In modeling studies in three-dimensional anisotropic porous media, Hemker et al (2004), Hemker and Bakker (2006) and Stauffer (2007) showed the existence of whirling streamlines which can considerably affect solute transport. The link between complex three-dimensional flow topology in heterogeneous anisotropic porous media and mixing has been addressed in a few recent modeling works (Bennet et al 2017;Chiogna et al 2014Chiogna et al , 2015Chiogna et al and 2016Cirpka et al 2015).…”