The Pore-network Modelling of the Infiltration Experiments Performed on Unsaturated Coarse Sands

2021 ◽  
Author(s):  
Tomáš Princ ◽  
Michal Snehota
Keyword(s):  
Hydraulic Conductivity ◽  
Network Model ◽  
Pore Network ◽  
Pore Network Model ◽  
Air Bubbles ◽  
Network Modelling ◽  
Air Content ◽  
Pore Network Modelling ◽  
X Ray Computed ◽  
Entrapped Air

<p>The research focused on the simulation of the previous experiment described by Princ et al. (2020). The relationship between entrapped air content (<em>ω</em>) and the corresponding satiated hydraulic conductivity (<em>K</em>) was investigated for two coarse sands, in the experiment. Additionally the amount and distribution of air bubbles were quantified by X-ray computed tomography.</p><p>The pore-network model based on OpenPNM platform (Gostick et al. 2016) was used to attempt simulation of a redistribution of the air bubbles after infiltration. Satiated hydraulic conductivity was determined to obtain the <em>K</em>(<em>ω</em>) relationship. The results from pore-network model were compared with the results from experiments.</p><p>Gostick et al. (2016). Computing in Science & Engineering. 18(4), p60-74.</p><p>Princ et al. (2020). Water. 12(2), p1-19.</p>

scholarly journals A Microfluidic Pore Network Approach to Investigate Water Transport in Fuel Cell Porous Transport Layers

2008 ◽  
Author(s):  
A. Bazylak ◽  
V. Berejnov ◽  
B. Markicevic ◽  
D. Sinton ◽  
N. Djilali
Keyword(s):  
Porous Media ◽  
Fuel Cell ◽  
Network Model ◽  
Pore Network ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Pore Network Model ◽  
Network Modelling ◽  
Pore Network Modelling ◽  
Microfluidic Networks

Pore network modelling has traditionally been used to study displacement processes in idealized porous media related to geological flows, with applications ranging from groundwater hydrology to enhanced oil recovery. Very recently, pore network modelling has been applied to model the gas diffusion layer (GDL) of a polymer electrolyte membrane (PEM) fuel cell. Discrete pore network models have the potential to elucidate transport phenomena in the GDL with high computational efficiency, in contrast to continuum or molecular dynamics modelling that require extensive computational resources. However, the challenge in studying the GDL with pore network modelling lies in defining the network parameters that accurately describe the porous media as well as the conditions of fluid invasion that represent realistic transport processes. In this work, we discuss the first stage of developing and validating a GDL-representative pore network model. We begin with a two-dimensional pore network model with a single mobile phase invading a hydrophobic media, whereby the slow capillary dominated flow process follows invasion percolation. Pore network geometries are designed, and transparent hydrophobic microfluidic networks are fabricated from silicon elastomer PDMS using a soft lithography technique. These microfluidic networks are designed to have channel size distributions and wettability properties of typical GDL materials. Comparisons between the numerical and experimental flow patterns show reasonable agreement. Furthermore, the fractal dimension and saturation are measured during invasion, revealing different operating regimes that can be applied to GDL operation. Future work for model development will also be discussed.

scholarly journals The Impact of Capillary Trapping of Air on Satiated Hydraulic Conductivity of Sands Interpreted by X-ray Microtomography

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 445 ◽  
Author(s):  
Tomas Princ ◽  
Helena Maria Reis Fideles ◽  
Johannes Koestel ◽  
Michal Snehota
Keyword(s):  
Hydraulic Conductivity ◽  
Air Bubbles ◽  
Air Entrapment ◽  
X Ray ◽  
Capillary Trapping ◽  
Air Content ◽  
X Ray Computed ◽  
Entrapped Air ◽  
The Impact ◽  
The Relationship

The relationship between entrapped air content and the corresponding hydraulic conductivity was investigated experimentally for two coarse sands. Two packed samples of 5 cm height were prepared for each sand. Air entrapment was created by repeated infiltration and drainage cycles. The value of K was determined using repetitive falling-head infiltration experiments, which were evaluated using Darcy’s law. The entrapped air content was determined gravimetrically after each infiltration run. The amount and distribution of air bubbles were quantified by micro-computed X-ray tomography (CT) for selected runs. The obtained relationship between entrapped air content and satiated hydraulic conductivity agreed well with Faybishenko’s (1995) formula. CT imaging revealed that entrapped air contents and bubbles sizes were increasing with the height of the sample. It was found that the size of the air bubbles and clusters increased with each experimental cycle. The relationship between initial and residual gas saturation was successfully fitted with a linear model. The combination of X-ray computed tomography and infiltration experiments has a large potential to explore the effects of entrapped air on water flow.

PORE NETWORK MODELLING OF FORMATION DAMAGE DUE TO SUSPENDED PARTICLES

2007 ◽  
Vol 47 (1) ◽  
pp. 189
Author(s):  
C. Gao ◽  
M. Rivero ◽  
E. Nakagawa ◽  
T. Rajeswaran
Keyword(s):  
Network Model ◽  
Particle Deposition ◽  
Drilling Fluid ◽  
Suspended Particles ◽  
Pore Network ◽  
Formation Damage ◽  
Pore Network Model ◽  
Core Flooding ◽  
Network Modelling ◽  
Different Characteristics

Formation damage caused by suspended particles takes place in various stages of drilling and production operations. The particles in drilling fluid, completion fluid, workover fluid, or injected water can clog the formation and cause severe reductions in productivity or injectivity. Related research has been conducted for years and the most widely used models are empirical, based on specific core flooding data. These models are easy to use; however, when they are applied to formations with different characteristics, the predictions are often rather poor.This work investigates a promising way to model formation damage at the pore level. Even though reservoir rocks have very different characteristics, they are all combinations of pore necks and pore bodies. In the proposed model, pore necks are represented by tubes and pore bodies are represented by globes to form a 2D network where particle deposition takes place. The pore size distribution is measured by porosimetry and assigned to the network. By adjusting the parameters of the pore necks and pore bodies, this pore network model can represent real porous media quite well. Surface deposition was considered to be the main mechanism of formation damage for small particles. The model was validated with lab test data and reasonable results were obtained. Compared with the empirical model, the pore network model could be applied to a much wider range of reservoirs.

Entrapment, stability, and persistence of air bubbles in soil water

Soil Research ◽  
1969 ◽  
Vol 7 (2) ◽  
pp. 79 ◽  
Author(s):  
AJ Peck
Keyword(s):  
Hydraulic Conductivity ◽  
Moisture Content ◽  
Soil Water ◽  
Unsaturated Soils ◽  
Equilibration Time ◽  
Air Bubbles ◽  
Air Entrapment ◽  
Water Characteristics ◽  
Spherical Bubbles ◽  
Entrapped Air

Air bubbles in soil water affect both hydraulic conductivity and moisture content at a given capillary potential. Consequently changes in the volume of entrapped air, which are not included in the specification of relationships between hydraulic conductivity, moisture content, and capillary potential, will affect all soil-water interactions. Current understanding of the process of air bubble entrapment during infiltration suggests that, in nature, significant air entrapment will often occur. It is shown that infiltrating water can dissolve only a very small volume of air, much less than the amount usually entrapped. Air bubbles in saturated soils are unstable since their pressure must exceed atmospheric, resulting in a diffusive flux of dissolved air from bubbles to menisci contacting the external atmosphere. However, stable bubbles are possible in unsaturated soils. Bubbles which are constrained by pore architecture to non-spherical shapes are usually stable, and spherical bubbles can be stable when the magnitude of the capillary potential exceeds about 3 bars. An approximate analysis of the characteristic time of bubble equilibration indicates that, in an example, it is of order 104 sec, but it may be greater or less by at least a factor 10. Since the equilibration time will be often at least as large as the period of significant soil temperature changes, it cannot be assumed that the entrapped air in a field soil is in an equilibrium state. In such circumstances unstable bubbles may be quasi-permanent. It is suggested that the slow growth of entrapped bubbles may account for the anomalously slow release of water observed in some outflow experiments. Changes of entrapped air volume may also account for the reported dependence of soil-water characteristics on the magnitude of the steps of capillary potential.

Sign in / Sign up

Export Citation Format

Share Document