scholarly journals Evaluation of hydrodynamic characteristics of porous media from one-step outflow experiments using RETC code

2018 ◽  
Vol 20 (3) ◽  
pp. 699-707 ◽  
Author(s):  
P. Londra ◽  
G. Kargas
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Unsaturated Soils ◽  
Simulation Models ◽  
Parametric Models ◽  
Water Retention Curve ◽  
Hydrodynamic Characteristics ◽  
Van Genuchten Model ◽  
One Step ◽  
Fitting Parameters

Abstract The ability of simulation models to accurately predict water flow and solute transport in unsaturated soils usually depends on the accuracy of the parametric models used to describe the water retention curve θ(h) and unsaturated hydraulic conductivity Κ(θ). Experiments were conducted to determine θ(h) and Κ(θ) relationships of six different porous media. θ(h) relationships were determined using Haines-type assembly or Richards' pressure cell chambers, depending on the soil type. K(θ) relationships were determined using the one-step outflow method. RETC code was used to analyze hydraulic properties. Experimental data were compared with those predicted by the Mualem-van Genuchten model using RETC for two prediction scenarios with three fitting parameters a, n, θr. The first scenario uses as input data the experimental θ(h) and saturated hydraulic conductivity (Ks) measurements and the second, the experimental θ(h), K(θ) and Ks measurements for two types of conductivity regression analysis. Concerning the second scenario, the Mualem model parameter p as an additional fitting parameter was also examined. Analysis of the results showed that the best method for predicting both the θ(h) and K(θ) relationships is to use simultaneously the experimental θ(h), K(θ) and Ks data with four fitting parameters a, n, θr, p.

scholarly journals Comparison of different estimation procedures for the hydraulic properties of horticultural substrates by One-Step technique

2013 ◽  
Vol 44 (2s) ◽  
Author(s):  
Carlo Bibbiani ◽  
Carlo A. Campiotti ◽  
Luca Incrocci ◽  
Alberto Pardossi
Keyword(s):  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Water Retention Curve ◽  
Step Method ◽  
Retention Curve ◽  
Van Genuchten Model ◽  
One Step ◽  
Conductivity Function ◽  
The One

The improved iterative method for the simultaneous determination of the hydraulic properties of growing media from One-Step experiment by Bibbiani, is performed and compared with simplified equations by Valiantzas and Londra. Brooks and Corey equation for water retention, and Kozeny power equation for hydraulic conductivity characterized the hydraulic properties of the porous media. The iterative procedure is applied on pure peat, pumice, and their mixes. The One- Step method has been previously optimized: processing the mean cumulative outflow curves recorded versus time, an estimation of diffusivity, and therefore of the hydraulic functions, is derived. Estimated water retention curve is compared with nine experimental data, and with the estimation of the Van Genuchten model, via the RETC code. Bibbiani’s and Van Genuchten’s models overlap except for the “very wet” range near saturation, whereas the Valiantzas and Londra’s procedure didn’t get satisfactory results. In regard to diffusivity, a good similarity between Bibbiani’s and Van Genuchten-Mualem’s curves can be assessed, while Valiantzas and Londra’s procedure generally results in higher values. Due to the lack of estimation of the water retention curve, Valiantzas and Londra’s procedure fails to estimate the hydraulic conductivity function, whereas Bibbiani’s and Van Genuchten-Mualem’s curves match together in most cases.

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.

scholarly journals Determining hydraulic properties of concrete and mortar by inverse modelling

2012 ◽  
Vol 1475 ◽  
Author(s):  
Sébastien Schneider ◽  
Dirk Mallants ◽  
Diederik Jacques
Keyword(s):  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Inverse Modelling ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Retention Data ◽  
Capillary Suction ◽  
Near Surface ◽  
Van Genuchten Model

ABSTRACTThis paper presents a methodology and results on estimating hydraulic properties of the concrete and mortar considered for the near surface disposal facility in Dessel, Belgium, currently in development by ONDRAF/NIRAS. In a first part, we estimated the van parameters for the water retention curve for concrete and mortar obtained by calibration (i.e. inverse modelling) of the van Genuchten model [1] to experimental water retention data [2]. Data consisted of the degree of saturation measured at different values of relative humidity. In the second part, water retention data and data from a capillary suction experiment on concrete and mortar cores was used jointly to successfully determine the van Genuchten retention parameters and the Mualem hydraulic conductivity parameters (including saturated hydraulic conductivity) by inverse modelling.

scholarly journals Capillary pressure–saturation curves of thin hydrophilic fibrous layers: effects of overburden pressure, number of layers, and multiple imbibition–drainage cycles

2019 ◽  
Vol 89 (23-24) ◽  
pp. 4906-4915 ◽  
Author(s):  
Amir Hossein Tavangarrad ◽  
S. Majid Hassanizadeh ◽  
Rodrigo Rosati ◽  
Luigi Digirolamo ◽  
Martinus Th van Genuchten
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Capillary Pressure ◽  
Unsaturated Soils ◽  
Measured Data ◽  
Text Data ◽  
Overburden Pressure ◽  
Number Of Layers ◽  
Thin Porous Media ◽  
Data Points

Unsaturated fluid flow in thin porous media depends on hydraulic properties, such as the capillary pressure, P c, as a function of saturation, S. We measured this relationship for two different types of compressible thin hydrophilic fibrous layers under varying conditions. Among other factors, we changed the number of layers and the overburden pressure (i.e. the confined solid pressure applied on top of the sample) imposed on one layer or a stack of layers. Applying an overburden pressure drastically affected the [Formula: see text] curves. However, increasing the number of fibrous layers had little impact on the capillary pressure–saturation curves. We also investigated the effect of multiple imbibition–drainage cycles on the [Formula: see text] data. Measured data points were used to find general expressions for the [Formula: see text] relationships of compressible thin porous media. Existing quasi-empirical correlations used in vadose zone hydrology, notably expressions by van Genuchten (Van Genuchten MTh. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci Soc Am J 1980; 44: 892-898) and Durner (Durner W. Hydraulic conductivity estimation for soils with heterogeneous pore structure. Water Resour Res 1994; 32: 211–223) for single- and dual-porosity media, respectively, were employed to fit the measured data points.

scholarly journals Relating Hydraulic Conductivity Curve to Soil-Water Retention Curve Using a Fractal Model

Mathematics ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 2201
Author(s):  
Carlos Fuentes ◽  
Carlos Chávez ◽  
Fernando Brambila
Keyword(s):  
Hydraulic Conductivity ◽  
Fractal Geometry ◽  
Water Retention ◽  
Water Movement ◽  
Darcy Law ◽  
Water Retention Curve ◽  
Hydrodynamic Characteristics ◽  
Soil Pressure ◽  
Retention Curve ◽  
Conductivity Curve

In the study of water transference in soil according to Darcy law, the knowledge of hydrodynamic characteristics, formed by the water retention curve θ(ψ), and the hydraulic conductivity curve K(ψ) are of great importance. The first one relates the water volumetric content (θ) with the water-soil pressure (ψ); the second one, the hydraulic conductivity (K) with the water-soil pressure. The objective of this work is to establish relationships between both curves using concepts of probability theory and fractal geometry in order to reduce the number of unknown functions. The introduction of four definitions used at the literature of the pore effective radius that is involve in the general model has permitted to establish four new specials models to predict the relative hydraulic conductivity. Some additional considerations related to the definitions of flow effective area and the tortuosity factor have allow us to deduce four classical models that are extensively used in different studies. In particular, we have given some interpretations of its empirical parameters in the fractal geometry context. The resulting functions for hydrodynamic characteristics can be utilized in many studies of water movement in the soil.

scholarly journals Coarse-Grained Geological Porous Media Structure Modeling Using Heuristic Algorithm and Evaluation of Porosity, Hydraulic Conductivity, and Pressure Drop with Experimental Results

2021 ◽  
Author(s):  
Javad Bezaatpour ◽  
Esmaeil Fatehifar ◽  
Ali Rasoulzadeh
Keyword(s):  
Particle Size ◽  
Porous Media ◽  
Hydraulic Conductivity ◽  
Pressure Drop ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Heuristic Algorithm ◽  
Flow In Porous Media ◽  
Coarse Grained ◽  
Water Retention Curve

Abstract Knowledge of porous media structure is an essential part of the hydrodynamic investigation of fluid flow in porous media. To study soil behavior (as a granular porous media) and water and contaminant movement in the vadose zone, appropriate estimation of soil water retention curve (SWRC) and soil hydraulic conductivity curve (SHCC) has a pivotal role and is one of the most challenging topics for researchers and engineers in soil and water science. The SWCR can be approximated using an accurate particle size distribution (PSD) function. In this study by applying random close packing (RCP) method as an encouraging method for predicting and studying particle configuration, an optimal particle size distribution is developed for coarse-grained soils (0.025 mm < PSD < 3.35mm). The mentioned RCP is generated using heuristic algorithm with merging applicable equations of soil science. For porous media modeling, MATLAB software is used and the predicted results by the optimal model for the parameters of porosity, pressure drop, and saturated hydraulic conductivity are compared with laboratory measurements. Experimental design is conducted by MINITAB and predicted coarse-grained soils structure by the model is compared with 4 sifted soils. The results of the sensitivity analysis showed that the porosity obtained from the model is strongly sensitive to the resolution factor and should be chosen with a sufficiently large amount (higher than 250). Results showed good consistency (up to 95%) between predicted porosity and only 10% difference in pressure drop and permeability with observed measurements.

scholarly journals Determination of the water diffusivity of horticultural substrates: comparison of different approaches for the one-step outflow data analysis

2014 ◽  
Vol 44 (4) ◽  
pp. 160
Author(s):  
Carlo Bibbiani ◽  
Carlo A. Campiotti ◽  
Luca Incrocci ◽  
Alberto Pardossi
Keyword(s):  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Pressure Head ◽  
Water Retention Curve ◽  
Water Diffusivity ◽  
One Step ◽  
Set Up ◽  
The One

The improved iterative method for the simultaneous determination of the hydraulic properties of growing media from one-step experiment by Bibbiani, was performed on pure peat, pure pumice, and peat/pumice (1peat:1pumice by volume) mix, and compared with simplified equations by Valiantzas and Londra, who set up a new two-point method for calculating the water diffusivity, and with Van Genuchten- Mualem model. Brooks and Corey equations for water retention and hydraulic conductivity characterized the hydraulic properties of the porous media in relation to the iterative procedure. In the present work, the estimated water retention curves are compared with nine experimental data, and with the estimation of the Van Genuchten- Mualem model, via the RETC code, taking into account retention and diffusivity data. Bibbiani’s and Van Genuchten-Mualem’s estimations overlap except for the very wet range near saturation (R<sup>2</sup> equals to 0.9997, 0.9999, 0.9998 for pure pumice, 1peat:1pumice mix, and pure peat respectively, for Bibbiani’s estimation; R<sup>2</sup> equals to 0.9923, 0.9541, 0.9993 for pure pumice, 1peat:1pumice mix, and pure peat respectively, for Van Genuchten-Mualem’s estimation), whereas the Valiantzas and Londra’s procedure didn’t get satisfactory results, apparently because of different requirements related to the final pressure head applied in one-step experiment. In regard to diffusivity, a good similarity between Bibbiani’s and Van Genuchten-Mualem’s curves can be assessed, being the mean ratio values of the D(θ) from Valiantzas equation divided by D(θ) from Bibbiani equation equal to 1.20, 1.10, and 1.31 for pure pumice, 1peat:1pumice mix, and pure peat respectively, while Valiantzas and Londra’s procedure generally results in higher values. Due to the lack of estimation of the water retention curve, Valiantzas and Londra’s procedure fails to estimate the hydraulic conductivity function, whereas Bibbiani’s and Van Genuchten-Mualem’s curves match together in most cases.

Unsaturated flow in coarse porous media

2005 ◽  
Vol 42 (1) ◽  
pp. 252-262 ◽  
Author(s):  
Jeff R Reinson ◽  
Delwyn G Fredlund ◽  
G Ward Wilson
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Soil Water ◽  
Unsaturated Soils ◽  
Unsaturated Flow ◽  
Characteristic Curve ◽  
Matric Suction ◽  
Coarse Grained ◽  
Capillary Barrier ◽  
Coarse Porous Media

Design of effective capillary barrier systems requires a thorough understanding of the soil–water interactions that take place in both coarse- and fine-grained unsaturated soils. Experimental observations of water flow through coarse porous media are presented to gain greater understanding of the processes and mechanisms that contribute to the movement and retention of water in coarse-grained unsaturated soils. The use of pendular ring theory to describe how water is held within a porous material with relatively low volumetric water contents is explored. Experimental measurements of seepage velocity and volumetric water content were obtained for columns of 12 mm glass beads using digital videography to capture the movement of a dye tracer front at several infiltration rates. An estimated curve for hydraulic conductivity versus matric suction is shown and compared to a theoretical curve. The method is shown to provide a reasonable predictive tool.Key words: soil-water characteristic curve, hydraulic conductivity curve, water permeability function, capillary barrier, matric suction.

Predicting the unsaturated hydraulic conductivity of granular soils from basic geotechnical properties using the modified Kovács (MK) model and statistical models

2006 ◽  
Vol 43 (8) ◽  
pp. 773-787 ◽  
Author(s):  
M Mbonimpa ◽  
M Aubertin ◽  
B Bussière
Keyword(s):  
Hydraulic Conductivity ◽  
Statistical Models ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Geotechnical Properties ◽  
Water Retention Curve ◽  
Granular Soils ◽  
Retention Curve ◽  
Unsaturated Hydraulic Conductivity ◽  
Preliminary Validation

The water retention curve (WRC) is often used to define the relative hydraulic conductivity, kr, of unsaturated soils. In this paper, the authors propose the use of the modified Kovács (MK) model, developed to predict the WRC using basic geotechnical properties, combined with some existing statistical models to estimate the kr function. The proposed equations are implemented in MATLAB®. After a preliminary validation based on comparisons with existing solutions, predictive results are presented for granular soils. These indicate a relatively good agreement with experimental results from drainage tests taken from the literature. A discussion follows on the advantages and limitations of the proposed approach.Key words: water retention curve, unsaturated hydraulic conductivity, predictive models, granular soils.

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