Experiment on Water Infiltration and Solute Migration in Porous and Fractured Media

2014 ◽  
Vol 955-959 ◽  
pp. 1993-1997 ◽  
Author(s):  
Jing Wen Song ◽  
Ming Yu Wang ◽  
Da Wei Tang
Keyword(s):  
Porous Media ◽  
Water Flow ◽  
Solute Concentration ◽  
Transport Processes ◽  
Fractured Media ◽  
Water Infiltration ◽  
Typical Structure ◽  
Fracture Structure ◽  
Flow Features ◽  
And Migration

The experiments were performed by considering the upper loose porous media and lower fractured media as a typical structure of vadose zones, and by constructing the corresponding physical model to simulate water flow and solute transport processes in order to investigate water flow features and migration mechanism. It has been indicated that in the porous and fractured complex media, if the lower fracture structure remains unchanged, the structure and permeability of the porous media offer considerable impact on infiltration processes. Additionally, if the structure and permeability of the porous media remain unchanged, the overall permeability and flow features of the fracture structure are significantly controlled by fracture configurations. Furthermore, for the fracture structures with different fracture configurations, it is indicated that increasing of the density of the vertical fractures results in much more enhancement of the solute concentration decay rate than that caused by increasing the density of the horizontal ones. This investigation was expected to be of scientific significance and practical value for effective groundwater protection.

Historical development of soil-water physics and solute transport in porous media

2007 ◽  
Vol 7 (1) ◽  
pp. 59-66 ◽  
Author(s):  
D.E. Rolston
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Solute Transport ◽  
Soil Water ◽  
20Th Century ◽  
Water Flow ◽  
Unsaturated Soils ◽  
Transport Processes ◽  
Transport In Porous Media ◽  
Unsaturated Hydraulic Conductivity

The science of soil-water physics and contaminant transport in porous media began a little more than a century ago. The first equation to quantify the flow of water is attributed to Darcy. The next major development for unsaturated media was made by Buckingham in 1907. Buckingham quantified the energy state of soil water based on the thermodynamic potential energy. Buckingham then introduced the concept of unsaturated hydraulic conductivity, a function of water content. The water flux as the product of the unsaturated hydraulic conductivity and the total potential gradient has become the accepted Buckingham-Darcy law. Two decades later, Richards applied the continuity equation to Buckingham's equation and obtained a general partial differential equation describing water flow in unsaturated soils. For combined water and solute transport, it had been recognized since the latter half of the 19th century that salts and water do not move uniformly. It wasn't until the middle of the 20th century that scientists began to understand the complex processes of diffusion, dispersion, and convection and to develop mathematical formulations for solute transport. Knowledge on water flow and solute transport processes has expanded greatly since the early part of the 20th century to the present.

Vadose Zone, Part I : Characterization and Flow Processes

2003 ◽  
Author(s):  
Yoram Rubin
Keyword(s):  
Porous Media ◽  
Water Flow ◽  
Governing Equation ◽  
Vadose Zone ◽  
Stochastic Analysis ◽  
Transport Processes ◽  
Richards Equation ◽  
Saturated Porous Media ◽  
Flow And Transport ◽  
Flow Processes

Many of the principles guiding stochastic analysis of flow and transport processes in the vadose zone are those which we also employ in the saturated zone, and which we have explored in earlier chapters. However, there are important considerations and simplifications to be made, given the nature of the flow and of the governing equations, which we explore here and in chapter 12. The governing equation for water flow in variably saturated porous media at the smallest scale where Darcy’s law is applicable (i.e., no need for upscaling of parameters) is Richards’ equation (cf. Yeh, 1998)

Microplastic water repellency impacts water flow and microplastic transport in soils

2021 ◽  
Author(s):  
Andreas Cramer ◽  
Pascal Benard ◽  
Anders Kaestner ◽  
Mohsen Zare ◽  
Andrea Carminati
Keyword(s):  
Porous Media ◽  
Water Flow ◽  
Capillary Rise ◽  
Water Repellency ◽  
Water Infiltration ◽  
Water Interface ◽  
Deuterated Water ◽  
X Ray ◽  
Air Water Interface ◽  
The Impact

<p>Soils are considered the largest sink of microplastic particles (MP) in terrestrial ecosystems. However, there is little knowledge on the implications of MP contaminating soils. In particular, we do not know the extent of and conditions under which MP are transported through porous media and, if they are deposited, how they affect soil hydraulic properties and soil moisture dynamics. We hypothesize that: 1) hydrophobic MP enhance soil water repellency; 2) isolated MP are displaced and transported by the air-water interface; 3) clusters of MP impede water flow and are retained in air-filled pores.</p><p>We tested these hypotheses in mixtures of MP (µm range) and sands (mm range) in a series of experiments. The Sessile Drop Method (SDM) was applied to measure the average contact angle (CA) of the mixtures for MP and model porous media in the same size range, ranging from 0 - 100 % MP content. Based on the specific surface and shape factor of MP and soil particles, the results are extrapolated to different MP and soil particle sizes. Capillary rise experiments were performed to measure the impact of MP on water infiltration. The applied MP contents of 0.35 % and 1.05 % reflect an average CA of 60° and 90° from the SDM extrapolation. Capillary rise of water and ethanol were carried out to estimate the apparent CA. Additionally and with the same MP content, we simultaneously imaged in three-dimensions the movement of deuterated water and MP during repeated drying / wetting cycles using X-Ray and Neutron tomography (at the beamline ICON, PSI). The different neutron attenuation coefficients of deuterated water and MP allows for estimating their distribution in the sand packing.</p><p>Already at MP contents of 5 % the CA measured with the SDM exhibited a steep increase and reached 59° to 81°, depending on the grain size of MP. The capillary rise experiments showed that MP reduce capillary rise. The apparent CA (43° and 53°) were smaller compared to the average CA from the SDM (60° and 90°), but the added MP increased air entrapment during capillary rise leading to a reduced saturation of the pore space (18 % and 16.5 %). Accumulation of MP at the advancing air-water interface was visible. Neutron and X-ray imaging showed at high resolution that regions with major MP content are water repellent and, are bypassed by water flow, and remain in air-filled pores.</p><p>Extrapolation of these results to soils suggests that in microregions with high MP contents, water infiltration is hindered. The low water content in these microregions might limit MP degradation due to reductions in: hydrolysis, coating of MP by e.g. dissolved organic substances, and colonization by microorganisms.</p>

Water flow mechanisms and unproductive water losses in rice-based cropping systems in the humid tropics

2021 ◽  
Author(s):  
Amani Mahindawansha ◽  
Philipp Kraft ◽  
Christoph Külls ◽  
Lutz Breuer
Keyword(s):  
Soil Water ◽  
Water Flow ◽  
Dry Season ◽  
Water Saving ◽  
Transport Processes ◽  
Water Infiltration ◽  
Wet Season ◽  
Water Losses ◽  
Flooded Rice ◽  
Flow Mechanisms

<p>In rice production areas in the world, increasing water scarcity is a major problem. Among the water saving techniques, integrating water saving non-flooded crops into the flooded rice system during the dry season is one of the promising water-saving approaches. Therefore, there is a necessity to improve the understanding of the water flow dynamics and losses in crop rotational systems under different climatic conditions in irrigated agricultural fields. That understanding can be used to lower the water requirements to build more efficient water management systems. We experimentally investigated the water flow processes and water losses by introducing non-flooded crops during the dry season (dry rice and maize) followed by flooded rice in the wet season and compared this to flooded rice in both seasons. We measured stable isotopes of water (δ<sup>2</sup>H and δ<sup>18</sup>O) in extracted soil water and liquid samples (Groundwater, ponded surface water, rainwater, and irrigation water). The Craig–Gordon equation was applied to estimate the fraction of evaporation losses. Results reveal that the soil isotopic profile patterns reflect the soil water transport processes and differ depending on the irrigation frequencies and crop diversification. Matrix flow and slow soil water infiltration, soil evaporation, and preferential flow via desiccation cracks were identified as the main water flow mechanisms in the irrigated fields. During the dry season, the evaporation effect on soil water is higher and water losses decreased from the beginning towards the end of the seasons. However, greater unproductive water losses were estimated during the wet season compared to the dry season. Finally, the results suggested that introducing dry seasonal crops to the crop rotation system for reducing the unproductive water losses is a good alternative method.</p><p> </p>

scholarly journals Modeling Flow and Transport in Unsaturated Porous Media: A Review

2000 ◽  
Vol 5 ◽  
pp. 265
Author(s):  
H.H. Al-Barwani ◽  
M. Al-Lawatia ◽  
E. Balakrishnan ◽  
A. Purnama
Keyword(s):  
Porous Media ◽  
Contaminant Transport ◽  
Water Flow ◽  
Unsaturated Zone ◽  
Unsaturated Flow ◽  
Numerical Solutions ◽  
Transport Processes ◽  
Field Conditions ◽  
Unsaturated Porous Media ◽  
Flow And Transport

Underground water is a vital natural resource and every effort should be made to understand ways and means of efficiently using and managing it. The unsaturated zone, bounded at its top by the land surface and below by the water table, is the region through which water, together with pollutant carried by the water, infiltrates to reach the groundwater. Therefore, various processes occurring within the unsaturated zone play a major role in determining both the quality and quantity of water recharging into the groundwater. Classical methods of predicting water flow and contaminant transport processes in unsaturated porous media are generally inadequate when applied to natural soils under field conditions, due to the occurrence of macropores, structured elements and spatial variability of soil properties. Contaminant transport models also require the simultaneous solution of the unsaturated flow and transport equations. For applications to field conditions, numerical solutions and computer simulations based on numerical models have been increasingly used. Advances and progress in modeling water flow and contaminant transport in the unsaturated zones are reviewed, and specific research areas in need of future investigation especially relevant to Oman are outlined.

Saturated and Unsaturated Water Flow in Inclined Porous Media

2004 ◽  
Vol 9 (2) ◽  
pp. 91-102 ◽  
Author(s):  
Scott W. Weeks ◽  
Graham C. Sander ◽  
Roger D. Braddock ◽  
Chris J. Matthews
Keyword(s):  
Porous Media ◽  
Water Flow ◽  
Unsaturated Water Flow

Modeling Transport in Porous Media With Phase Change: Applications to Food Processing

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
Amit Halder ◽  
Ashish Dhall ◽  
Ashim K. Datta
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Food Processing ◽  
Transport Processes ◽  
Phase Changes ◽  
Solid Matrix ◽  
Deep Fat Frying ◽  
Modeling Framework ◽  
Food Manufacturing ◽  
Food Processes

Fundamental, physics-based modeling of complex food processes is still in the developmental stages. This lack of development can be attributed to complexities in both the material and transport processes. Society has a critical need for automating food processes (both in industry and at home) while improving quality and making food safe. Product, process, and equipment designs in food manufacturing require a more detailed understanding of food processes that is possible only through physics-based modeling. The objectives of this paper are (1) to develop a general multicomponent and multiphase modeling framework that can be used for different thermal food processes and can be implemented in commercially available software (for wider use) and (2) to apply the model to the simulation of deep-fat frying and hamburger cooking processes and validate the results. Treating food material as a porous medium, heat and mass transfer inside such material during its thermal processing is described using equations for mass and energy conservation that include binary diffusion, capillary and convective modes of transport, and physicochemical changes in the solid matrix that include phase changes such as melting of fat and water and evaporation/condensation of water. Evaporation/condensation is considered to be distributed throughout the domain and is described by a novel nonequilibrium formulation whose parameters have been discussed in detail. Two complex food processes, deep-fat frying and contact heating of a hamburger patty, representing a large group of common food thermal processes with similar physics have been implemented using the modeling framework. The predictions are validated with experimental results from the literature. As the food (a porous hygroscopic material) is heated from the surface, a zone of evaporation moves from the surface to the interior. Mass transfer due to the pressure gradient (from evaporation) is significant. As temperature rises, the properties of the solid matrix change and the phases of frozen water and fat become transportable, thus affecting the transport processes significantly. Because the modeling framework is general and formulated in a manner that makes it implementable in commercial software, it can be very useful in computer-aided food manufacturing. Beyond its immediate applicability in food processing, such a comprehensive model can be useful in medicine (for thermal therapies such as laser surgery), soil remediation, nuclear waste treatment, and other fields where heat and mass transfer takes place in porous media with significant evaporation and other phase changes.

Porous media as a canvas for hydro-bio-geo-chemical processes: Facing the challenges

2021 ◽  
Author(s):  
Xavier Sanchez-Vila
Keyword(s):  
Porous Media ◽  
Reactive Transport ◽  
Field Work ◽  
Open Science ◽  
Transport Processes ◽  
Aquifer Recharge ◽  
Music Production ◽  
Emerging Compounds ◽  
Technological Developments ◽  
Large Research

<p>The more we study flow and transport processes in porous media, the larger the number of questions that arise. Heterogeneity, uncertainty, multidisciplinarity, and interdisciplinarity are key words that make our live as researchers miserable… and interesting. There are many ways of facing complexity; this is equivalent as deciding what colors and textures to consider when being placed in front of a fresh canvas, or what are the sounds to include and combine in a music production. You can try to get as much as you can from one discipline, using very sophisticated state-of-the-art models. On the other hand, you can choose to bring to any given problem a number of disciplines, maybe having to sacrifice deepness in exchange of the better good of yet still sophisticated multifaceted solutions. There are quite a number of examples of the latter approach. In this talk, I will present a few of those, eventually concentrating in managed aquifer recharge (MAR) practices. This technology involves water resources from a myriad of perspectives, covering from climate change to legislation, from social awareness to reactive transport, from toxicological issues to biofilm formation, from circular economy to emerging compounds, from research to pure technological developments, and more. All of these elements deserve our attention as researchers, and we cannot pretend to master all of them. Integration, development of large research groups, open science are words that will appear in this talk. So does mathematics, and physics, and geochemistry, and organic chemistry, and biology. In any given hydrogeological problem you might need to combine equations, statistics, experiments, field work, and modeling; expect all of them in this talk. As groundwater complexity keeps amazing and mesmerizing me, do not expect solutions being provided, just anticipate more and more challenging research questions being asked.</p>

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