Minimum Pore Diameter Research Articles

Study on the Impact of Porous Media on Condensate Gas Depletion: A Case Study of Reservoir in Xihu Sag.

During the depletion and pressure reduction process in condensate gas reservoirs, the precipitation of condensate oil transforms the single-phase gas flow into a two-phase gas-liquid flow, significantly reducing the permeability. Currently, microscopic studies of the phase behavior of condensate gas in porous media mainly focus on observing and describing the occurrence of condensate oil, lacking quantitative calculations and direct observations of condensate oil throughout the entire depletion cycle. This paper uses a microvisualization method to simulate the depletion process of condensate gas reservoirs. Condensate gases with oil contents of 175.3 and 505.5 g/cm3 were prepared by mixing methane, ethane, hexane, and decane in specific proportions. Pore structures were extracted from thin sections of real core casts, and microfluidic chips with a minimum pore diameter of 20 μm and an areal porosity of 20.75% were fabricated by using a chemical wet etching method. Subsequently, microfluidic condensate gas depletion experiments were conducted with chip images recorded during the depletion process. Grayscale analysis of the depletion images was performed using ImageJ software to quantitatively calculate condensate oil saturation and recovery rates, analyzing the effects of different condensate oil contents on condensate gas depletion, and comparing the differences between depletion in porous media and in a PVT cell. The conclusions drawn are as follows: the dew points of high and low in the porous media are 3.15% and 1.85% higher than those in the PVT cell, respectively. In the early stages of depletion, condensate oil saturation in porous media is higher than that in the PVT cell, while in the middle to late stages, condensate oil saturation in porous media is lower than that in the PVT cell. The condensate oil recovery rate in porous media is significantly higher than the depletion recovery rate in the PVT cell. Condensate oil tends to precipitate and disperse at blind ends and corners, while it easily forms patches in mainstream large pores.

Effect of combined parametric impacts on collapsing the wall quality of WAAM Al5356 component

Even though Wire and Arc Additive Manufacturing (WAAM) of the Al5356 component has garnered attention for making affordable, large-scale components, problems with porosity, humping, and undercut still exist. Therefore, optimising process parameters is crucial to achieving flawless products with consistent layer deposition. Hence in this research, the most important WAAM parameters including travel speed (TS), wire feed speed (WFS), and torch angle (TA), were examined in order to determine how they affected structural integrity while taking into account key responses such as porosity, pore diameter, and tensile strength. The Significance of Criteria Weighted Aggregated Sum Product Assessment (WASPAS) in conjunction with Intercriteria Correlation (CRITIC) was used to investigate the favourable circumstances and confirm that the TA is the most important parameter in the nucleation of pores. The verification studies demonstrate that a 58.2 % reduction in pore diameter results in a 31.8 % increase in tensile strength. An ideal TS and WFS of 65 cm/min and 5 m/min, with a maximum TA of 90°, were found to be the favorable conditions for printing Al5356 wall with a minimum porosity of 0.037 %, enhanced ultimate tensile strength of 278 MPa, and minimum pore diameter of 93 µm, according to the CRITIC associated WASPAS approach. Additionally, using the fractography, the damage process based on the porosity creation was investigated. The optimal parameters for generating a defect-free multi-layer structure were identified, hence enhancing the structure’s suitability for industrial use.

Investigations of Water Transport in Shale Reservoir with Dual-Wettability by Using Monte Carlo Method.

How liquids transport in the shale system has been the focus because of fracturing fluid loss. In this study, a single-nanopore model is established for liquid transport in shale while considering the slip effect and effective viscosity of confined fluids. Then, the fractal Monte Carlo (FMC) model is proposed to upscale the single-pore model into shale porous media. The effects of different transport mechanisms, shale wettability, and pore characteristic parameters on confined liquid flow in shale rock are investigated. Results show that FMC permeabilities are 2-3 orders of magnitude larger than intrinsic and slip-corrected permeabilities in organic matter. However, the slip effect and effective viscosity have little influence on water flow in inorganic matter. With the contact angle of organic pore (θom) increasing and contact angle of inorganic pore (θin) decreasing, the effective permeability of the whole shale matrix grows in number. The enhancement factor in the situation of θom = 170° and θin = 20° is 4 orders of magnitude larger than the case of θom = 130° and θin = 40°, although the close effective macroscopic contact angle (θeff = 80°) occurs in these two cases, which indicates that shale microscopic wettability has a significant impact on the confined liquid transport. Moreover, with the increase of porosity and maximum pore diameters, shale permeability increases rapidly, but the enhancement factor has the opposite trend. Compared with the tiny impact of the variance of minimum inorganic pore diameters, minimum organic pore diameters have more significant impacts on liquid flow in shale systems, and the enhancement factor also rapidly increases up to 30 times for the case of 0.5 nm because of the strong slip effect.

Multifractal approach for a biological porous media: Human dentin case.

A multifractal characterization to human dentin porosity is made. Micrographs of human dentin samples gotten from scanning electron microscopy (SEM) were studied in order to characterize porosity. We got the generalized dimensions (multifractal moments) for pore space and matrix skeleton on gray scale and binary images for samples of both gender. For the case, we found that superficial porosity is linked to mass fractal dimension in an approximately linear relationship as for binary images. In addition, probability density distribution (PDD) for pore diameters is found a normal PDD type. Other quantities of interest like mean, standard deviation, maximum and minimum pore diameters, voit ratios, and percentage of chemical composition are reported. RESEARCH HIGHLIGHTS: SEM sample, images and procedure for multifractal analysis are detailed. Micro patterns in grayscale are multifractal and in binary scale are monofractals. Superficial porosity is relate to mass fractal dimension approximately linearly. From the porosity values, voit ratios are determined. Pores diameters obey a normal PDD.

Pore Permeability Model Based on Fractal Geometry Theory and Effective Stress

AbstractA reasonable coal seam permeability model should be established to accurately estimate the extraction effectiveness of coalbed methane (CBM). Existing permeability models typically ignore the influence of pore structure parameters on the permeability, leading to an overestimation of the measured permeability, and consequently, the CBM production cannot be effectively predicted. This paper presents a novel permeability model based on discrete pore structures at the micro–nano scale. The model considers the interaction between the pore fractal geometry parameters, coal deformation, and CBM transport inside these pores. The contributions of key pore geometry parameters, including the maximum pore diameter, minimum pore diameter, porosity, and fractal dimensions, to the initial permeability were investigated. A numerical analysis showed that the influence of fractal dimension on the permeability is finally reflected in the influence of pore structure parameters. The initial permeability is exponential to the minimum pore diameter and proportional to the maximum pore diameter and porosity. In addition, the macroscopic permeability of the coal is positively correlated with the maximum pore diameter, minimum pore diameter, and porosity, with the minimum pore diameter having the most significant influence on the permeability evolution process. This research provides a theoretical foundation for revealing the gas flow mechanism within coal seams and enhancing the extraction effectiveness of CBM.

A microporous MgO-MgAl2O4 functional refractory for small inclusions removal of tundish: Preparation and parameters optimization

A microporous MgO–MgAl2O4 gas-permeable brick was fabricated for use in tundish to remove small inclusions in liquid steel using argon bubbles, based on the optimization of particle gradation. The effect of activated alumina addition on the properties and pore size distribution of microporous MgO–MgAl2O4 bricks was investigated. The flow rate parameters of argon for inclusion removal were optimized. The results showed that the microporous MgO–MgAl2O4 permeable brick, prepared by adding 5 wt% activated alumina, had a minimum average pore diameter of 10.9 μm and greater air permeability compared to no introduction of activated alumina. The thermal stability was significantly improved due to the long cone-shaped magnesium-rich spinels generated by the solid-state reaction between magnesium oxide and activated alumina distributed in the pores; this further remodeled the structure of the pores. The addition of more activated alumina caused a sharp drop in the volume density and strength and formed more spinels, with the morphology of spinels changing from long cone to octahedron with larger average pore size; these are not beneficial to the production and application of gas-permeable brick. When the flow rate was 60 L/min, the total oxygen content (T.[O]) in the billet was reduced by 7 ppm, the content of pores and cracks in the billet decreased dramatically, and the removal rates of inclusion size distributions of 20–50 μm, 50–100 μm, and >100 μm in the billets increased by 15%, 20%, and 61%, respectively.

High performance porous carbon derived from Platanus leaves for a solid-state supercapacitor

Porous carbons materials have attracted immense interest on account of the well-developed porosity and adjustable surface chemistry. In this study, a Platanus leaves-based porous carbons (PLPCs) with a large specific surface area were prepared by the simple pre‑carbonization and KOH activation method. The morphology and structure of the PLPCs were systematically characterized by TGA, SEM, TEM, XRD, Raman, and N2 adsorption/desorption techniques. The effects of the amount of KOH and the activation temperature on the pore structure and electrochemical property of the samples were discussed. The produced PLPCs have a large specific surface area (up to 1709.82 m2 g−1) and a minimum average pore diameter (1.89 nm). The as-prepared electrode exhibits a specific capacitance of 379 F g−1 at a current density of 1 A g−1 and an excellent cycling stability of 117% over 5000 charge/discharge cycles. The PLPCs samples are employed to fabricate a solid-state supercapacitor (SSCs) and exhibit superior specific capacitance of 186 F g−1 and high energy density of 25.8 Wh kg−1.

Single nucleotide discrimination with sub-two nanometer monolayer graphene pore

The effective sensing area is the key point of solid-state nanopore single-molecule detection, which is determined by the diameter of the hole and the thickness of the membrane. High spatial resolution can be achieved by using single-atom thickness two-dimensional materials, such as single-layer graphene and molybdenum disulfide. Helium ion beam microscopy provides an effective technique for manufacturing small-sized nanopores. Here, we show that the precise fabrication of sub-2 nanometer nanopores has been successfully achieved on a single-layer graphene film, which provides the best spatial resolution in room-temperature ionic liquid-assisted single-molecule detection. Many graphene nanopores of different sizes have been fabricated, with a minimum pore diameter of 1.4 nm. The application of these graphene nanopores manufactured by HIM shows that single-layer graphene nanopores can distinguish different homopolymer single-stranded DNA lengths and types, and can even identify four single nucleotides.

Utilization of Citrus aurantium peels for sustainable production of high surface area type I microporous nano activated carbons

Orange (Citrus aurantium) peel was investigated for producing microporous nano activated carbons (OPAC). One-step chemical activation process by zinc chloride as an activating agent and a carbonization temperatures ranging from 500 to 900 °C was used to produce OPAC having high surface area of type I. The effects of carbonization temperature, impregnation ratio, and impregnation time on the properties of the OPAC were studied. The prepared activated carbons were characterized by FTIR; Brunauer–Emmett–Teller (BET); TGA; TEM, SEM, and EDAX analyses; the point of zero charge; and Boehm titration method. The maximal surface area of OPAC was activated by using the impregnation (orange peel/ZnCl2) ratio of 2:1, 700 °C carbonization temperature, and a 30-min holding time. The BET surface area, the total pore volume, and the micropore volume were 1228.2 m2/g, 0.5516, and 0.5482 cm3/g, respectively. The total pore volume increased with the increase of the activation temperature. The minimum pore diameter was 0.7 nm and the mean pore diameter was 1.797 nm. The results proved that the ZnCl2 chemical activation is a useful technique to prepare high surface area activated carbon from Citrus aurantium peels with nano pore size structure.

A study on the flowability of gas displacing water in low-permeability coal reservoir based on NMR technology

Flowability of gas and water through low-permeability coal plays crucial roles in coalbed methane (CBM) recovery from coal reservoirs. To better understand this phenomenon, experiments examining the displacement of water by gas under different displacement pressures were systematically carried out based on nuclear magnetic resonance (NMR) technology using low-permeability coal samples of medium-high coal rank from Yunnan and Guizhou, China. The results reveal that both the residual water content (Wr) and residual water saturation (Sr) of coal gradually decrease as the displacement pressure (P) decreases. When P is 0–2 MPa, the decline rates of Wr and Sr are fastest, beyond which they slow down gradually. Coal samples with higher permeability exhibit higher water flowability and larger decreases in Wr and Sr. Compared with medium-rank coal, high-rank coal shows weaker fluidity and a higher proportion of irreducible water. The relationship between P and the cumulative displaced water content (Wc) can be described by a Langmuir-like equation, Wc = WLP/(PL + P), showing an increase in Wc in coal with an increase in P. In the low-pressure stage from 0 to 2 MPa, Wc increases most rapidly, while in the high-pressure stage (P > 2 MPa), Wc tends to be stable. The minimum pore diameter (d′) at which water can be displaced under different displacement pressures was also calibrated. The d′ value decreases as P increases in a power relationship; i.e., d′ the coal gradually decreases with the gradual increase in P. Furthermore, the d′ values of most of the coal samples are close to 20 nm under a P of 10 MPa.

FRACTAL ANALYSIS OF SURFACE ROUGHNESS EFFECTS ON GAS DIFFUSION IN POROUS NANOFIBERS

Fractal model of gas diffusion in porous nanofibers with rough surfaces is derived, in which the porous structure is assumed to be composed of a bundle of tortuous capillaries whose pore size distribution and surface roughness follow the fractal scaling laws. The analytical expression for gas relative diffusion coefficient is a function of the relative roughness and the other microstructural parameters (porosity, the fractal dimension for pore size distribution and tortuosity, the maximum and minimum pore diameter and the characteristic length). The proposed fractal model is validated by comparison with available experimental data and correlations. At the same time, the effect of microstructural parameters of porous fibrous materials on gas diffusion has been studied in detail. It is believed that the current model may be extended to porous materials other than fibrous materials.

Preparation and Component Optimization of Resin-Based Permeable Brick

The present study aims to prepare resin-based permeable bricks with micron-sized pores using fine aggregate with a particle diameter of 0.08–0.6 mm and bisphenol-A epoxy resin, a polymer binder. The properties of the binder, the characteristic parameters of the aggregate, and the micro pore structure of the brick were studied in order to break through the limitations of traditional porous permeable materials. The dynamic mechanical properties of resin were analyzed by dynamic mechanical analysis (DMA). The frequency parameter of particle size of 10 kinds of aggregate from different regions were obtained by digital image processing, and the characteristic parameter (aggregate distribution coefficient α) was obtained by modified Gaussian distribution. The microstructure of porous brick was analyzed by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). The test results show: (1) the glass transition temperature (Tg) of the resin is 61 °C; (2) the parameters of aggregate particle group will affect the performance of porous permeable materials; (3) the minimum effective pore diameter of the permeable brick is 30 μm, the maximum permeable rate is and the compressive strength is 41.08 MPa. The conclusions of this study will provide an important reference for permeable materials in the micron-scale pore range and the selection of binder and aggregate materials.

Revealing pore connectivity across scales and resolutions with X‐ray CT

AbstractConnectivity is one of the most important parameters to quantify pore structure and link it to soil functions. One of the great challenges in quantifying connectivity with X‐ray microtomography (X‐ray μCT) is that high resolution, as required for small pores, can only be achieved in small samples in which the connectivity of larger pores can no longer be quantified in a meaningful way. The objective of this study was to investigate the changes in pore connectivity with changing sample size, covering a range of analysed pore diameters of more than three orders of magnitude. With this approach, we wanted to address whether pore types formed by different processes in an agricultural chronosequence leave characteristic traces in certain connectivity metrics. The Euler number, χ, and the connection probability of two random points within the pore system, that is, the Γ‐indicator, were determined as a function of minimum pore diameter. The results show that characteristic signatures of certain pore types overlap with scale artifacts in the connectivity functions. The Γ‐indicator, gives highly biased information in small samples. Therefore, we developed a new method for a joint‐Γ‐curve that merges information from three samples sizes. However, χ does not require such a scale fusion. It can be used to define characteristic size ranges for pore types and is very sensitive to the occurrence of bottle necks. Our findings suggest a joint evaluation of both connectivity metrics to disentangle different pore types with χ and to identify the contribution of different pore types to the overall pore connectivity with Γ. This evaluation on the chronosequence showed that biopores mainly connect pores of diameters between 0.5 and 0.1 mm. This was not coupled with an increase in pore volume. In contrast, tillage led to a shift of pores of diameter >0.05 mm towards pores of diameter >0.20 mm and thus increased connectivity of pores >0.20 mm. This work underlines the importance of accounting for the scale dependence of connectivity measures and provides a methodological approach for doing so.Highlights Scale dependence of connectivity metrics needs to be accounted for. Connectivity metrics can be used to disentangle different pore types across scales. Roots mainly connect the pore system between 0.1 and 0.5 mm. A joint Γ‐connectivity function can be constructed that is free of scale artifacts.

Scale and REV analyses for porosity and pore connectivity measures in undisturbed soil

Soil samples with a volume of approximately 100 mL are commonly used for measuring soil properties needed to parameterize continuum models of transport processes in soils. The necessary assumption that the sampled soil volume corresponds to a representative elementary volume (REV) has only been occasionally tested. Furthermore, the few studies so far have focused on bulk properties such as porosity and bulk density and have not investigated the scale-dependence of pore-space connectivity, which is fundamental for transport properties such as the permeability of soil. In this study, we investigated the scale-dependence of morphologic properties of the soil pore-space in 25 undisturbed soil columns sampled from five different depths (8, 23, 33, 53 and 73 cm) from a field site in southern Norway (Skuterud). We conducted the analyses of scale-dependence on regions of interests of 40 × 40 × 40 mm3 from binarized X-ray images with a resolution of 40 µm. We focused our evaluation on imaged porosity and three measures of pore-space connectivity (the connection probability, the Euler-Poincaré number and the critical pore diameter). As pore network connectivity is scale-dependent and because the connectivity of large pores has a very strong impact on the soil permeability, we conducted our analyses considering three contrasting minimum pore diameters, namely 80, 250 and 500 µm.We found that the pore connectivity improved with scale, predominantly due to the presence of pores with diameters of less than 0.25 mm. This stresses the importance of image resolution in scale analyses. We moreover observed that both the mean and the standard deviation of the critical pore diameter increased with scale, which may explain why the mean and standard deviation of the saturated hydraulic conductivity are often found to increase with scale. We detected an REV range for the macroporosity between approximately 15 and 65 mm. This range decreased with an increase in the minimum pore diameter considered. However, we also found evidence contradicting the existence of the detected REV range for the macroporosity due to a lack of statistical homogeneity. No REV range could be found for the three investigated connectivity measures, probably because the evaluated scales were too small. Based on our results we conclude that larger soil samples should be used to measure soil properties and investigate processes that depend on the pore network connectivity, such as permeability or water flow and long-range solute transport. We recommend that future studies should investigate REVs for connectivity measures and investigate which REV criteria are most meaningful in a continuum modelling context. Such studies are needed to evaluate whether REVs for transport properties are common in soils. If not, flow and transport models that explicitly account for heterogeneity are necessary.

Control of the pore size of honeycomb polymer film from micrometers to nanometers via substrate-temperature regulation and its application to photovoltaic and heat-resistant polymer films

Honeycomb porous polystyrene (PS) films with an aspect ratio of pore depth to pore diameter at approximately 1.0 were fabricated using the breath figure (BF) method. Two modes of water droplet coalescence in the pore growth were observed in real-time by optical microscopy. Pore size significantly increases with the increase in humidity and the decrease in substrate temperature. The porous pattern could emerge even at room temperature under high humidity of 80%. Boiling point and solvent density significantly influence the pore distribution and pore depth. Chloroform and tetrahydrofuran achieve more uniform hexagonal patterns than benzene and dichloromethane. Subsequently, to obtain nanometer porous PS film, the fast-evaporation BF process was designed by regulating the gradient substrate temperature and evaporation time, and porous mesoscopic PS film was obtained. The minimum pore diameter and corresponding pore depth are about 120 nm and 27 nm, respectively. Finally, the fast-evaporation BF process was applied to the honeycomb film formation of photovoltaic polymer poly(3-hexylthiophene) (P3HT), and the heat-resistant polymers polysulfone (PSF) and polyimide (PI).

Relative Permeability Model Taking the Roughness and Actual Fluid Distributions into Consideration for Water Flooding Reservoirs

Reservoir relative permeability is greatly important to the development of water flooding reservoirs. Currently, most researches on relative permeability have not taken the roughness of pore surface and actual fluid distributions into consideration. In this paper, a novel relative permeability model for water flooding reservoirs taking the roughness and actual fluid distributions into consideration has been proposed by using the fractal theory. The novel model contains some key parameters, all of which have clear physical meanings, such as the immobile liquid film thickness, relative roughness, tortuosity fractal dimension $$ D_{\text{T}} $$ and pore fractal dimension $$ D_{\text{f}} $$ . The predicted results of the novel fractal relative permeability model are consistent with published experimental data. That verifies the correctness of the novel fractal relative permeability model. Finally, sensitive factor analysis of novel relative permeability model is conducted. We can find that the wetting fluid relative permeability decreases as the immobile wetting fluid film thickness or relative roughness increases. When the tortuosity fractal dimension or pore fractal dimension increases, the wetting relative permeability and non-wetting relative permeability will both decrease. An increase in maximum pore diameter or the decreasing of minimum pore diameter results in the reduction in fractal dimension of flow channel and discontinuous saturation. The increasing of maximum pore diameter results in an increase in the relative permeability of wetting fluid. The minimum pore diameter has tiny effect on the relative permeability.

Characterization of Mechanical and Micro-Architectural Properties of Porous Hydroxyapatite Bone Scaffold Using Green MicroAlgae as Binder

Novel Hydroxyapatite (HA)-based porous bone scaffold is developed using green microalgae as binding as well as pore-forming agent. The composite scaffolds are developed at 1:2, 2:1 and 1:1 (w/w) compositions of HA and binder, respectively, using solvent-casting technique and their mechanical and micro-architectural properties are investigated. Material characterization of the scaffold shows improved mechanical strength with a maximum compressive strength of 2.89 MPa and maximum interconnected porosity of 65.29%. FT-IR and XRD results confirm formation of crystalline nano-HA in the scaffolds. SEM and TEM micrographs of the scaffolds show pore morphology with a maximum pore diameter of 258 microns and minimum pore diameter of 6 microns and uniformly dispersed rod-shaped nano-HA particles of length 3.95–99.11 nm, respectively. TG/DTG analysis shows high thermal stability of scaffolds with high HA content. Comparative study of the three types of scaffolds shows composites with equal weight ratio of HA, and binder yields the highest porosity and mechanical strength desired for cell growth and support. XRF analysis confirms Ca and P as the major constituent elements of the scaffold. The study highlights the potential of natural biomass as an alternative to synthetic and naturally derived polymeric binders for development of HA-based bone scaffolds.

Modelling imbibition data for determining size distribution of organic and inorganic pores in unconventional rocks

Recent studies show that the pore network of unconventional rocks generally consists of inorganic and organic parts, forming a dual-wet medium. The organic part has high wetting affinity to oleic phase but low wetting affinity to aqueous phase. In contrast, the inorganic part has high wetting affinity to both oleic and aqueous phases. The objective of this study is to estimate the organic and inorganic pore size distributions (PSDs) of the unconventional rocks by analyzing the comparative oil and brine imbibition data. A previously-proposed fractal model which considers the non-piston-like imbibition front is used to achieve this objective. We use a history matching technique to fit the measured imbibition data with the proposed fractal model, and determine unknown parameters such as fractal dimension (FD), minimum pore diameter (Dmin), and tortuosity (τ) that control the imbibition profile. The determined parameters are then used to estimate PSD. The PSD of inorganic and organic pores (PSDinorg+org) is calculated by oil imbibition data and the PSD of inorganic pores (PSDinorg) is calculated by brine imbibition data. The PSD of organic pores (PSDorg) is calculated by decoupling of PSDinorg+org and PSDinorg.Comparing the estimated PSDorg and PSDinorg shows that organic pores are generally smaller than inorganic pores, consistent with the results of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses, indicating the abundance of nanopores within the organic matter. Moreover, compared with the PSD from mercury injection capillary pressure (MICP) test, PSD estimated by oil imbibition shows very small pores (< 3 nm in diameter) which are not accessible by mercury, especially for the low-permeability rock samples. The method proposed in this study can complement the conventional MICP technique for a more comprehensive characterization of the pore network of unconventional rocks with dual-wet pore network.

FRACTAL MODEL OF GAS DIFFUSION THROUGH POROUS FIBROUS MATERIALS WITH ROUGH SURFACES

Fractal model of gas diffusion through porous fibrous materials with rough surfaces is derived, in which the porous structure is simplified to be composed of a bundle of tortuous capillaries whose pore size distribution and surface roughness follow the fractal scaling laws. The analytical expression for gas relative diffusion coefficient is a function of the relative roughness, fiber radius and the other microstructural parameters (porosity, the fractal dimension for pore size distribution and tortuosity, the maximum and minimum pore diameter and the characteristic length). The proposed fractal model is validated by comparison with available experimental data and correlations. At the same time, the effect of microstructural parameters of porous fibrous materials on gas diffusion has been studied in detail. It is believed that the current model may be extended to porous materials other than fibrous materials.

Predicting the soil water retention curve from the particle size distribution based on a pore space geometry containing slit-shaped spaces

Abstract. Traditional models employed to predict the soil water retention curve (SWRC) from the particle size distribution (PSD) always underestimate the water content in the dry range of the SWRC. Using the measured physical parameters of 48 soil samples from the UNSODA unsaturated soil hydraulic property database, these errors were proven to originate from an inaccurate estimation of the pore size distribution. A method was therefore proposed to improve the estimation of the water content at high suction heads using a pore model comprising a circle-shaped central pore connected to slit-shaped spaces. In this model, the pore volume fraction of the minimum pore diameter range and the corresponding water content were accordingly increased. The predicted SWRCs using the improved method reasonably approximated the measured SWRCs, which were more accurate than those obtained using the traditional method and the scaling approach in the dry range of the SWRC.