scholarly journals Influence of Grain Size Transition on Flow and Solute Transport through 3D Layered Porous Media

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 5) ◽  
Author(s):  
Zhi Dou ◽  
Xueyi Zhang ◽  
Jinguo Wang ◽  
Zhou Chen ◽  
Yunbo Wei ◽  
...  
Keyword(s):  
Grain Size ◽  
Porous Medium ◽  
Porous Media ◽  
Flow Field ◽  
Solute Transport ◽  
Transition Zone ◽  
Significant Influence ◽  
Local Flow ◽  
Layered Porous Media ◽  
Distribution Of Flow

Abstract Soils and other geologic porous media often have contrasting grain size layers associated with a grain size transition zone between layers. However, this transition zone is generally simplified to a plane of zero thickness for modeling assumption, and its influence has always been neglected in previous studies. In this study, an approach combining a deposition process and a random packing process was developed to generate 3D porous media without and with consideration of the transition zone. The direct numerical models for solving the flow and concentration fields were implemented to investigate the influence of the grain size transition on flow and solute transport. Our results showed that although the transition zone occupied 13.6% of the entire layered porous medium, it had little influence on the distribution of flow velocity at the scale of the entire layered porous medium. However, the transition zone had a significant influence on the local flow field, which was associated with the increased spatial variability of velocity and the varied distribution of flow velocity. This varied local flow field could increase the solute residence time and delay the breakthrough time for solute transport. Although using both the advection-dispersion equation (ADE) and the mobile and immobile (MIM) models to fit the breakthrough curves (BTCs) for solute transport through layered porous media resulted in trivial errors, the ADE model failed to capture the influence induced by the local flow field, especially the influence of the transition zone. In contrast, the MIM model was shown to be able to capture the influence of the transition on solute transport. It was found that the mass transfer rate α, a parameter of the MIM model, was significantly improved by the presence of the transition zone, while it decreased as the transition zone fraction increased. Our study emphasized that the transition zone can vary the local flow field at the pore scale, while it has little influence on the hydraulic properties (e.g., hydraulic conductivity) of the macroscale flow field. However, the local flow field varied by the transition zone has a significant influence on solute transport.

Diffusion limited mixing in heterogeneous porous media

2021 ◽  
Author(s):  
Mayumi Hamada ◽  
Pietro de Anna
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Flow Field ◽  
Fast Diffusion ◽  
Pore Scale ◽  
Mixing Processes ◽  
Local Flow ◽  
Gaussian Shape ◽  
Diffusion Limited ◽  
The Impact

<p><span><span>A pore-scale description of the transport and mixing processes is particularly relevant when looking at biological and chemical reactions. For instance, a microbial population growth is controlled by local concentrations of nutrients and oxygen, and chemical reaction are driven by molecular-scale concentration gradients. The heterogeneous flow field typically found in porous media results from the contrast of velocities that deforms and elongates the mixing fronts between solutes that often evolves through a lamella-like topology. For continuous Darcy type flow field a novel framework that describes the statistical distribution of concentration being transported was recently developed (Le Borgne et al., JFM 2015). In this model, concentrations in each lamella are distributed as a Gaussian-like profile which experiences diffusion in the transverse direction while the lamella is elongated by advection along the local flow direction. The evolving concentration field is described as the superposition of each lamella. We hypothesize that this novel view, while perfectly predicting the distribution of concentration for Darcy scale mixing processes, will breakdown when the processes description is at the pore scale. Indeed the presence of solid and impermeable boundaries prevents lamella concentration to diffuse freely according to the a Gaussian shape, and therefore changes the mixing front profile, the lamella superposition and elongation rules. P</span></span><span><span>revious work (Hamada et al, PRF, 2020) demonstrated that </span></span><span><span>the presence of solid boundaries leads to an enhanced diffusion and thus fast homogenization of concentrations. </span></span><span><span>In a purely diffusive process the local mixing time is reduced by a factor of ten with respect to the </span></span><span><span>continuous case and concentration gradient are dissipated exponentially fast while a </span></span><span><span>power law decrease </span></span><span><span>is </span></span><span><span>observed in continuous medium.</span></span><span><span> To investigate the impact of these mechanisms on mixing we developed a</span></span><span><span>n experimental set-up to visualize and quantify the displacement of a conservative tracer in a synthetic porous medium. The designed apparatus allows to obtain high resolution concentration measurement</span></span><span><span>s</span></span><span><span> at the pore scale. We show that the resulting mixing measures, computed in terms of concentration probability density function and dilution index values, diverge </span></span><span><span>qualitatively and quantitatively from what happens in a continuous domain. These observations suggest </span></span><span><span>that description of pore-scale diffusion-limited mixing requires model that takes into account the confined nature of porous medium, </span></span><span><span>otherwise we will tend to overestimate concentration value and neglect the fast diffusion dynamic taking place at microscopic level.</span></span></p>

Propagation of acoustic waves in layered porous media

2007 ◽  
Vol 5 ◽  
pp. 169-175
Author(s):  
V.L. Dmitriev ◽  
Е.А. Ponomareva
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Dispersion Relation ◽  
Acoustic Waves ◽  
Saturated Liquid ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Layered Porous Media ◽  
The Media

The paper considers the processes of reflection and transmission acoustic waves at the interface between two porous media, saturated liquid or gas. The cases of a porous medium whose layers have the same porosity, but are saturated with different fluids. Based The dispersion relation and the conditions at the interface between the media are obtained reflection and transmission coefficients. The possibility determination of the parameters of the porous material and its saturating fluid based on the signal reflected from the interface.

scholarly journals Mathematical Treatment of Saturated Macroscopic Flow in Heterogeneous Porous Medium: Evaluating Darcy’s Law

Hydrology ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 4
Author(s):  
R. William Nelson ◽  
Gustavious P. Williams
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Flow Field ◽  
Laboratory Experiments ◽  
Heterogeneous Media ◽  
Darcy’S Law ◽  
Heterogeneous Porous Media ◽  
Darcy's Law ◽  
Mathematical Treatment ◽  
Heterogeneous Porous Medium

We present a rigorous mathematical treatment of water flow in saturated heterogeneous porous media based on the classical Navier-Stokes formulation that includes vorticity in a heterogeneous porous media. We used the mathematical approach proposed in 1855 by James Clark Maxwell. We show that flow in heterogeneous media results in a flow field described by a heterogeneous complex lamellar vector field with rotational flows, compared to the homogeneous lamellar flow field that results from Darcy’s law. This analysis shows that Darcy’s Law does not accurately describe flow in a heterogeneous porous medium and we encourage precise laboratory experiments to determine under what conditions these issues are important. We publish this work to encourage others to perform numerical and laboratory experiments to determine the circumstances in which this derivation is applicable, and in which the complications can be disregarded.

Sign in / Sign up

Export Citation Format

Share Document