Full Range Of Saturation Research Articles

Thermal conductivity of dried biocemented sand at higher calcification

Thermal conductivity of dried biocemented sand at higher calcification

Shear–induced anisotropy in granular materials under various saturation states

This study presents a micromechanical study on the characteristics of shear-induced anisotropy in granular media under various saturation states. A series of unsaturated triaxial compression tests under the full range of degree of saturation are performed by using Discrete Element Method (DEM). The effect of the suctions on the characteristics of anisotropy is illustrated and discussed. Good agreements between anisotropy and stress ratio are observed for saturated and unsaturated states if skeleton contact stress is adopted. With the increase of the suctions, the weight of fabric tensor anisotropy decreases while the weight of anisotropy related to normal forces increases. The mechanical anisotropy plays a dominant role in providing shear resistance for the full saturation range.

Pore-by-Pore Modelling, Validation and Prediction of Waterflooding in Oil-Wet Rocks Using Dynamic Synchrotron Data

We predict waterflood displacement on a pore-by-pore basis using pore network modelling. The pore structure is captured by a high-resolution image. We then use an energy balance applied to images of the displacement to assign an average contact angle, and then modify the local pore-scale contact angles in the model about this mean to match the observed displacement sequence. Two waterflooding experiments on oil-wet rocks are analysed where the displacement sequence was imaged using time-resolved synchrotron imaging. In both cases the capillary pressure in the model matches the experimentally obtained values derived from the measured interfacial curvature. We then predict relative permeability for the full saturation range. Using the optimised contact angles distributed randomly in space has little effect on the predicted capillary pressures and relative permeabilities, indicating that spatial correlation in wettability is not significant in these oil-wet samples. The calibrated model can be used to predict properties outside the range of conditions considered in the experiment.

Effects of topological disorder in unsaturated granular media via a pore-scale lattice Boltzmann investigation

In this study, we investigate the impact of topological disorder on liquid distribution and transport phenomena in three-dimensional unsaturated granular media using the Shan-Chen lattice Boltzmann method. Distinct samples of disordered media are generated, characterized by the disorder index Iv. Under different Iv, varied liquid cluster distributions are demonstrated in a gravity-driven vapour-liquid system. Gradually increasing the initial liquid phase in the simulation domain allows the full range of saturation. The focuses are placed on the liquid cluster statistics from the connectivity, total cluster number, largest cluster and mean cluster volume at an increasing saturation. Meanwhile, the interfacial area, liquid retention curves and relative permeability-saturation curves are produced at diverse Iv and wettability. It is found that the slopes of retention curves are well correlated with the proposed capillary index Ic that unifies both disorder and wettability. The proposed generalized correlation between capillary index and slope index is useful in terms of determining the capillary pressure-saturation curve and relative permeability-saturation curve for a given granular system at varied contact angles. Additionally, the cohesive strength-saturation curves are also obtained with the aid of the interfacial area and negative capillary pressure, which elucidates that a packing with a higher Iv experiences a relatively larger cohesive strength. These results enhance the understanding of disorder effect and will be beneficial for the exploration of many retention curves-related phenomena such as liquid transfer and stress-strain relation for wet granular media.

Pore-Scale Modeling of Fluid-Fluid Interfacial Area in Variably Saturated Porous Media Containing Microscale Surface Roughness.

A pore-scale model is developed to simulate fluid-fluid interfacial area in variably saturated porous media, with a specific focus on incorporating the effects of solid-surface roughness. The model is designed to quantify total (film and meniscus) fluid-fluid interfacial area (Anw ) over the full range of wetting-phase fluid saturation (Sw ) based on the inherent properties of the porous medium. The model employs a triangular pore space bundle of cylindrical capillaries (BCC) framework, modified with three surface roughness-related parameters. The first parameter (surface roughness factor) represents the overall magnitude of surface roughness, whereas the other two parameters (interface growth factor and critical adsorptive film thickness) reflect the micro-scale structure of surface roughness. A series of sensitivity analyses was conducted for the controlling variables, and the efficacy of the model was tested using air-water interfacial area data measured for three natural porous media. The model produced good simulations of the measured Anw data over the full range of saturation. The results demonstrate that total interfacial areas for natural media are typically much larger than those for ideal media comprising smooth surfaces due to the substantial contribution of surface roughness to wetting-film interfacial area. The degree to which fluid-fluid interfacial area is influenced by roughness is a function of fluid-retention characteristics and the nature of the rough surfaces. The full impact of roughness may be masked to some degree due to the formation of thick wetting films, which is explicitly quantified by the model. Application of the model provides insight into the importance of the interplay between pore-scale distribution and configuration of wetting fluid and the surface properties of solids.

Effective thermal conductivity of sands estimated by Group Method of Data Handling (GMDH)

Effective thermal conductivity (ETC), the ability of soil mass to dissipate heat is of vital scientific and engineering interest for many subsurface energy storage and transportation processes. Many mathematical, empirical, semi-empirical and numerical methods are available to compute the ETC. However, these methods offer a specific solution to a considered soil type but are limited by boundary conditions and the time of computation in case of numerical methods which are more general in nature and could be applied to a wider range of soil types. Neural networks due to superior prediction capabilities have attracted much attention in the recent past. Here, in this paper we apply Group Method of Data Handling (GMDH) from the class of neural network due to superior abilities in effectiveness of input parameter scaling and less computation time. Standard errors are calculated, and the model used to predict the ETC of two sands of different texture, mineralogical composition for full range of saturation. The model predicted experimental results are in good agreement for the pure quartz sand but for quartz-feldspar the model over predicts the ETC. The method is general and could be applied for wide range of geomaterial for effective parameter identification.

Pore-scale modelling of relative permeability of cementitious materials using X-ray computed microtomography images

Permeability of cementitious materials is an important durability indicator. In practice, concrete is rarely saturated. Therefore, it is essential to study permeability of unsaturated cementitious materials. This paper presents an integrated modelling approach for estimating permeability of cementitious materials over the full range of saturation. An in-house code based on multiphase and single-phase lattice Boltzmann models is developed and used to simulate the moisture distribution and fluid flow in unsaturated cement paste with various curing ages, the 3D microstructures of which are obtained from X-ray micro-CT. The water permeability and gas permeability of partially saturated cement paste are then estimated. The results indicate with decreasing water saturation water permeability decreases while gas permeability increases. Additionally, the moisture distribution and permeability of unsaturated cement paste are strongly dependent on its microstructure. Moreover, there exists a unique relationship between permeability and effective porosity. The simulation results show good agreement with experimental data.

Prediction of soil solid thermal conductivity from soil separates and organic matter content: computational micromechanics approach

Evaluation of soil thermal conductivity at a given saturation usually requires the value of conductivity in the saturated state, which is commonly estimated by the geometric mean from the conductivities of water and soil solids (λs). Therefore, an accurate estimate of λs has a marked effect on soil conductivity within the full range of saturation. In this research, we modelled the soil solid as a multi‐phase medium comprising individual isotropic phases with conductivities drawn randomly from an assumed probability density function. The variation in the thermal conductivity of minerals is associated with the corresponding soil separates: clay, silt and sand. A computational micromechanics approach was used to evaluate the homogenized thermal conductivity of the soil solids with different fractions of soil separates and organic matter contents. A new formula to predict λs is proposed by fitting a four parameter, non‐linear function to the numerical results. Thirty experimental results of soil conductivities at saturation (our investigations and literature data) were used to validate the proposed model. We show that the new approach improves analytical predictions in terms of the root mean square error and bias. The proposed model to estimate λs is suitable for practical purposes because it requires information on the fraction of sand and organic matter contents only.HighlightsCan we predict conductivity of solids from soil separates and organic matter only? Soil skeleton is modelled at the mineralogical scale as a multiphase material. Conductivity of soil solids has considerable effect on assessment of conductivity in the saturated state. Proposed model makes possible the efficient evaluation of thermal conductivity of soil solids.

Thermal Conductivity of Binary Sand Mixtures Evaluated through Full Water Content Range

Core Ideas Thermal conductivity and water content relationship based upon mixtures are distinct. Systematic change in particle fine fraction directly affects thermal conductivity. Strong correlation between density and thermal conductivity Campbell model well predicts thermal conductivity with all four parameters calibrated. Lu and Dong model well predicts thermal conductivity with both parameters calibrated. A soil's grain‐size distribution affects its physical and hydraulic properties; however, little is known about its effect on soil thermal properties. To better understand how grain‐size distribution affects soil thermal properties, specifically the effective thermal conductivity, a set of laboratory experiments was performed using binary mixtures of two uniform sands tightly packed with seven different mixing fractions over the full range of saturation. For each binary mixture, the effective thermal conductivity, λ, capillary pressure, hc, and volumetric water content, θ, were measured. Results demonstrated that the λ–θ relationship exhibited distinct characteristics based on the percentage of fine‐ and coarse‐grained sands. We further compared measured λ–θ properties with independent estimates from two semi‐empirical models (Campbell Model and Lu and Dong Model) to evaluate the models' applicability in relation to physically based parameters associated with changes in soil mixing (e.g., porosity and grain size). Both models were able to fit experimental data but to varying degrees based on the number of physically based parameters used. In general, model improvements are needed to capture the λ–θ relationship solely on physically based parameters.

Thermal Conductivity of Standard Sands. Part III. Full Range of Saturation

The thermal conductivity $$(\lambda )$$ of three unsaturated standard quartz sands (Ottawa C-109 and C-190, and Toyoura) was measured by a transient thermal-conductivity probe, at room temperature of approximately $$25\,^{\circ }\text{ C }$$ and at loose and tight compactions. The measurements were carried out at different degrees of saturation $$(S_\mathrm{r})$$ from dryness to full saturation. In general, a sharp $$\lambda $$ increase was observed at low $$S_\mathrm{r}$$ , followed by a moderate rise until full saturation. However, experiments on loosely compacted C-190 samples revealed $$\lambda $$ deviation from a general trend ( $$\lambda $$ vs $$S_\mathrm{r})$$ caused by water percolation. Alternatively, successful experiments were carried out on loosely packed unsaturated C-190 samples using 1 % agar gel. For loosely compacted C-109 and Toyoura, $$\lambda $$ data obtained from 1 % agar gel closely agreed with $$\lambda $$ data for water as a saturation medium. The measured data were used to verify a model by de Vries for unsaturated soils. The model largely underestimates experimental data at $$S_\mathrm{r}<0.5$$ and produces an overall root-mean-square error of about $$0.2\, \text{ W }~{\cdot }~\text{ m }^{-1}~{\cdot }~\text{ K }^{-1}$$ . Measured $$\lambda $$ data agreed with data by a steady-state technique (a guarded hot-plate apparatus) at dryness and full saturation and exceeded the steady-state data in the unsaturated region. However, TCP data can be considered more reliable due to a lower temperature increase during $$\lambda $$ measurements and a shorter testing time. Consequently, in the case of unsaturated soils, evaporation and migration of water and steam can be avoided.

Dependence of the Electrical Conductivity on Saturation in Real Porous Media

Archie's Law for the porosity and saturation dependence of electrical conductivity, σ(θ) = aσbϕm(θ/ϕ)n (where σ is electrical conductivity, the subscript b denotes the brine or bulk solution, ϕ is porosity, θ is volume wetness, and a, m, and n are fitting parameters) was recently derived by applying continuum percolation theory to fractal porous media. We have recast Archie's Law in terms of saturation alone to obtain σ(θ) = σ0 (θ − θc)μ, where θc is the critical volume fraction for percolation, and σ0 = aσb/(1 − θc)μ. The value of the exponent, μ = 2.0 for three‐dimensional systems and 1.28 for two, is consistent with theory and simulations. We examined the universality of the exponent's value, and the range of validity of our expression. Drawing on published data, we compared predicted and measured values of σ(θ) across the full range of saturation, and found that the newly derived expression provides good predictions, is robust with respect to secondary effects such as residual salinity and contact resistance, and yields meaningful physical parameters.

Lab-Grown Colored Diamonds From Chatham Created Gems

developments in recent years has been the commercial availability of jewelry-quality synthetic diamonds. What for almost three decades was primarily an industrial or research product is now becoming a commodity in the gem and jewelry marketplace. In addition to the products being offered by such companies as the Gemesis Corp. and Lucent Diamonds, Chatham Created Gems of San Francisco, California, has introduced a line of synthetic diamonds from a new source (figure 1). This article presents results of our examination of a large group of these high pressure/high temperature (HPHT) laboratory-grown diamonds in yellow, blue, green, and pink colors showing a full range of saturation, from weak to strong. Our examination indicates that most of the yellows and blues represent “as-grown” colors (i.e., those produced by nitrogen and boron impurities during diamond crystallization), while the greens and pinks are the result of either growth or growth plus post-growth treatment processes (i.e., irradiation, with or without subsequent heating). A single manufacturer is supplying Chatham Created Gems with approximately 500 carats of synthetic diamond crystals per month, with future increases in production planned (T. Chatham, pers. comm., 2004). The material is faceted in China into cut goods that range from a few points (melee) to as large as 2 ct. Chatham Created Gems is the sole distributor of this material for jewelry purposes. Previous gemological reports on synthetic diamonds produced in Russia and sold by Mr. Chatham (see, e.g., Scarratt et al., 1996) may not be applicable to the new HPHT-grown material described here, which is grown in Asia with a non-BARS press. This article provides information on material from all four color categories of this new product, including descriptions of green and pink synthetic diamonds, which have not been reported on extensively in the gemological literature. Most of the green samples display this color because they contain both blue and yellow growth sectors. Some of this new material displays hues and weaker saturations that more closely resemble natural diamonds

A comparison of relative nonwetting‐phase permeability models

We compared three groups of models commonly used to describe the dependence of relative nonwetting‐phase permeability on phase saturation in porous media and tested the capability of these models to predict relative air permeabilities using two experimental data sets. The first group of models is purely empirical, involving no fitting parameters. In models of the second type, denoted here as geometry‐based models, relative nonwetting‐phase permeability is derived from the wetting‐phase retention curve on the basis of an idealized concept of pore space geometry. According to these models, nonwetting‐phase permeability should vary over the full range of saturation and should be a function of total nonwetting‐phase saturation. In models of the third type this variation is limited to a narrower range based on the concept that only part of the nonwetting phase contributes to permeability and assuming that the relationship between the “effective” saturation of this continuous nonwetting phase can be described by the same mathematical functions as between total nonwetting‐phase saturation and relative permeability in the geometry‐based models. Since this implies some kind of analogy, we refer to this group of models as “analogy‐based.” We found that matching the saturation at which nonwetting‐phase permeability emerges, i.e., the emergence point, is crucial for the description or prediction of relative nonwetting‐phase permeability in the range of high wetting‐phase saturations. Using analogy‐based models which were derived from the geometry‐based models by simply rescaling the effective saturation range to fit this endpoint, predictions were found to depend sensitively on whether the Burdine or the Mualem model was chosen to relate the permeability function to the retention curve. Differences between these two approaches were found to be primarily due to the different exponents in the tortuosity term. When we made this parameter flexible and determined it by curve‐fitting from measured data, we obtained very good fits of experimental air permeabilities.

A Bulk and Spatially Resolved NMR Relaxation Study of Sandstone Rock Plugs

A detailed study of the proton nuclear magnetic-resonance spin–lattice and spin–spin relaxation time of water in a series of 10 well-characterized sandstone rock plugs has been made as a function of saturation. The saturation levels range from 0.06%, equivalent to monolayer coverage of the surface of the pore space, to 100%. Both bulk and spatially resolved measurements have been made. The results have been used to test fast-diffusion relaxation theory in rock over the full saturation range for the first time. Evidence has been obtained for the effect of pore throats on the relaxation rates for each plug and estimates have been made of pore-throat sizes which correlate well with water-vapor percolation thresholds.

Simple mixing technique for the preparation of blood samples of known oxygen saturation

A mixing technique for the preparation of whole blood samples of known oxygen saturation is described. The technique, which uses basic equipment and a very simple procedure, is capable of accuracies better than ±2% across the full range of saturation and is extendable to use with other applications with only slight reductions in accuracy.

A framework for the prediction of saturation properties: liquid densities

Abstract Shaver R.D., Robinson R.L., Jr. and Gasem K.A.M., 1992. A framework for the predic- tion of saturation properties: liquid densities. Fluid Phase Equilibria, 78: 81-98. Our scaled-variable-reduced-coordinate framework for correlating saturation properties was applied to pure-fluid saturated liquid densities at temperatures from the triple point to the critical point. The new correlation represents the saturated liquid densities of diverse chemical species with average errors of 0.11% when two adjustable parameters are used to characterize each substance. This compares favorably with the modified Rackett and the Hankinson-Thomson correlations with the added advantages of covering the full saturation range and obeying scaling-law behavior in the near-critical region. The correlation framework is essentially empirical; however, the results suggest an underlying physical significance for the model parameters, which show an excellent poten- tial for generalized predictions. This is demonstrated by the results given here where generalized saturated liquid density predictions over the full saturation range yield average errors of less than 1.0%.

A framework for the prediction of saturation properties: vapor pressures

A new framework is proposed for correlating saturation properties using a ‘scaled-variable-reduced-coordinate’ approach. Utility of this approach is demonstrated by correlating the vapor pressures of a number of compounds at temperatures from the triple point to the critical point. The new framework results in precise representation of vapor pressures of diverse chemical species, generally within their experimental uncertainties (%AAD within 0.1) when two adjustable parameters are used to characterize each substance. The proposed model compares favorably with existing correlations, while having the added advantages of covering the full saturation range and obeying scaling-law bahavior in the near-critical region. Although the approach is essentially empirical, results obtained suggest an underlying physical significance for the model parameters and show an excellent potential for generalized predictions. This is demonstrated by the results given here for vapor pressures, where generalized predictions yield average errors of less than 1.5% over the full saturation range, based on a single experimental measurement.