Article
Geosciences, Multidisciplinary
Li Fengxia, Zeng Fanhui, Shen Yunqi, Zhang Yu
Summary: A new fractal relative permeability model is proposed in this study, which takes into account multiple factors influencing permeability. The accuracy of the model is verified by comparing with earlier models and experimental data. The research shows that in shale reservoirs, the relative permeability of the gas phase gradually decreases with increasing water saturation, the effect of confined viscosity varying with nanopore diameter is greater on inorganic pores than on organic pores, and the relative permeability of the intersection point in organic pores is higher than that of inorganic pores.
FRONTIERS IN EARTH SCIENCE
(2022)
Article
Computer Science, Interdisciplinary Applications
He Chen, Shi-Jin Feng
Summary: This study evaluates the abilities of fractal-based hydraulic constitutive models in describing two-phase flows and investigates their application in NAPL-contaminated low-permeability sites. Comparison with experimental results shows that the fractal model accurately describes the two-phase flow behavior. The fractal dimension and intrinsic permeability of soils significantly affect the flow, and the lower part of the low-permeability layer is recommended as the main fracturing and injection zone for optimal efficiency.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Computer Science, Interdisciplinary Applications
J. Machacek, W. Fuentes, P. Staubach, H. Zachert, T. Wichtmann, Th. Triantafyllidis
Summary: The Theory of Porous Media (TPM) has been used to derive governing equations for unsaturated soils. However, most works neglect the effects of residual water and entrapped air. This study deduces a set of governing equations that consider these effects and examines the theory's performance in water retention curve simulations and a dynamic analysis of a dam subjected to earthquake loading.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Soil Science
You Gao, Ze Li, De'an Sun, Haihao Yu
Summary: Reliable estimation of unsaturated soil hydraulic properties is crucial for various research and engineering projects. The study evaluated hydraulic hysteresis and permeability of unsaturated soil with different void ratios or bulk densities. Results showed that the proposed hysteresis model effectively describes the drying, wetting, and scanning curves at different void ratios, and the permeability model predicts the relative permeability coefficient accurately.
SOIL & TILLAGE RESEARCH
(2021)
Article
Computer Science, Interdisciplinary Applications
He Chen, Shi-Jin Feng
Summary: This study develops a generalized constitutive model to describe hydraulic properties of soils considering soil heterogeneity and water distribution. The model assumes pore size distribution as a fractal characteristic and includes water retention curve, relative water permeability curve, and relative air permeability curve. Validation results show that the proposed model predicts relative water permeability and relative air permeability of unsaturated soils well. It also outperforms other models for most data sets. The influence of dual-porosity characteristic of structured soils on hydraulic properties is addressed.
COMPUTERS AND GEOTECHNICS
(2022)
Article
Engineering, Geological
Mohamad Chaaban, Yousef Heider, Waiching Sun, Bernd Markert
Summary: The paper investigates the utilization of artificial neural networks (ANNs) in learning models to address the nonlinear anisotropic flow and hysteresis retention behavior of deformable porous materials. Simulations and databases are used to model single-phase and biphasic flow, and two different ML approaches are compared for the accuracy and speed of training. The outcomes demonstrate the capability of ML models in accurately and efficiently representing constitutive relations for permeability and hysteretic retention curves.
INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS
(2023)
Article
Mathematics, Interdisciplinary Applications
Khoa M. Tran, Ha H. Bui, Giang D. Nguyen
Summary: A new hybrid numerical approach is proposed to model unsaturated seepage flows through porous media by combining discrete and continuum methods. The method is capable of describing the nature of flow in unsaturated porous media at the microscale level and simulating water flow through heterogeneous porous media without any ad hoc treatments. The method can be applied to various methods possessing similar features, with a focus on its application to the discrete element method (DEM).
COMPUTATIONAL PARTICLE MECHANICS
(2022)
Article
Construction & Building Technology
Stephane Poyet
Summary: Cement-based materials are increasingly recognized as fractal materials, with fractal scaling laws used to describe the pore size distribution. This study generated virtual fractal porous media based on bundles of parallel cylindrical pores, and estimated their capillary curve and permeability using theoretical and numerical approaches. The results suggest that the van Genuchten equation, although lacking a physical basis, contains fractal information, but may not perfectly fit capillary curves and could introduce errors in inverse analysis. Additionally, there appears to be a relationship between intrinsic permeability and the van Genuchten pressure parameter.
CEMENT AND CONCRETE RESEARCH
(2021)
Article
Geosciences, Multidisciplinary
Nguyen Van Nghia A., Damien Jougnot, Luong Duy Thanh, Phan Van Do, Tran Thi Chung Thuy, Dang Thi Minh Hue, Nguyen Manh Hung
Summary: This study develops a model to predict the permeability of porous media saturated by one or two fluid phases using a fractal upscaling technique. The model takes into account microstructural properties such as fractal dimension and porosity, and performs well compared to existing models.
HYDROGEOLOGY JOURNAL
(2021)
Article
Engineering, Geological
Yousef Heider, Hyoung Suk Suh, WaiChing Sun
Summary: This paper presents a meta-modeling approach that utilizes deep reinforcement learning to automatically discover optimal neural network settings for the machine learning constitutive laws. By replacing the human modeler to handle the optimized choices of setup, the AI agent self-learns from taking a sequence of actions within the selection environment. The resulting ML-generated material models can be integrated into a finite element solver to solve initial-boundary-value problems.
INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS
(2021)
Article
Mathematics, Interdisciplinary Applications
Tongjun Miao, Aimin Chen, Yan Xu, Sujun Cheng, Liwei Zhang, Changbin Yan, Boming Yu
Summary: This study proposes analytical models for the dimensionless relative permeabilities of wetting and non-wetting phases flow in porous-fracture media based on fractal geometry theory. The results reveal that the ratio between porous matrix and fracture significantly affects the relative permeabilities and total saturations of wetting phases.
FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY
(2021)
Article
Mathematics, Interdisciplinary Applications
Zuozhuang Yin, Siliang Duan, Xiuya Guo, Huili Wang, Ruijuan Chen, Qian Zheng
Summary: Gas permeability of fractal porous media with rough surfaces is modeled using a probability model and simulated numerically. The model considers both Poiseuille flow and Knudsen flow mechanisms and can be described by structural parameters such as pore fractal dimension, tortuosity fractal dimension, relative roughness, and porosity. The model is validated by comparing with experimental data and shows good agreement. The predicted results show that gas permeability decreases with increasing relative roughness and tortuosity fractal dimension, and increases with increasing porosity and pore fractal dimension. Our gas permeability model provides insights into the physical mechanisms of gas transport in porous media with rough surfaces.
FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY
(2023)
Article
Water Resources
Stephan K. Matthai, Luat K. Tran
Summary: Performance assessment of CO2 storage sites requires realistic modeling of the impact of heterogeneous aquifer properties on brine-CO2 flow. A new workflow for the computation of equivalent relative permeability is presented using a novel continuum-scale flow solver. The workflow is demonstrated on samples from a potential CO2 storage site in Australia and an outcrop analogue model from Argentina.
ADVANCES IN WATER RESOURCES
(2023)
Article
Engineering, Environmental
Fatma Louati, Houcem Trabelsi, Yahya Alassaf, Mehrez Jamei, Said Taibi
Summary: This paper aims to experimentally study the unsaturated permeability (K-unsat) of a clayey soil during desiccation. It was demonstrated that K-unsat was well related to the initial state in terms of density and moisture content. When the suction reaches the entry suction value, K-unsat decreases when the suction increases without the appearance of desiccation cracks. Otherwise, it increases with the growing intensity of the cracks.
BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT
(2023)
Article
Agronomy
Zhongkui Chen, Viroon Kamchoom, Rui Chen, Lapyote Prasittisopin
Summary: The application of biochar as an environmentally friendly additive for agricultural soils has gained attention, but its impact on unsaturated hydraulic behavior at high suction ranges is understudied. This study investigates the influence of biochar addition on the unsaturated hydraulic properties of biochar amended soil (BAS), considering biochar content, particle size, and soil compaction. Results show that soil compaction has a diminishing effect on BAS's unsaturated hydraulic properties at high suction range. High compaction reduces saturated permeability by minimizing soil macropores. However, incorporating high biochar contents with fine particles enhances the reduction of unsaturated permeability and improves water holding capacity, making biochar an effective application for soil sustainability.
Article
Mathematics, Interdisciplinary Applications
Xianwu Qiao, Yuqing Shen, Xiaohua Tan, Shuxia Qiu, Zhouting Jiang, Agus Pulung Sasmito, Peng Xu
Summary: The dissimilar multi-scale structures of shale make it difficult to understand the fluid flow and heat transfer in unsaturated shale formations. In this study, the pore structure and moisture content of shale samples were measured, and a pore-scale model was developed based on the fractal scaling law. The model successfully predicted the effective and relative permeability, as well as the effective thermal conductivity, and showed the importance of capillary pressure and gas slippage in multiphase flow through unsaturated shale.
FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY
(2022)
Article
Polymer Science
Qun Zhang, Dongqing Shao, Peng Xu, Zhouting Jiang
Summary: This study investigated the effect of pulsed and oscillating electric fields on the conformational properties of all-alpha proteins. Molecular dynamics simulations were used to analyze the structural characteristics of the protein samples. The results showed that higher frequencies of the electric field influenced the rapid response to secondary structural transitions, but had a diminished effect on conformational changes measured by RMSD. The dipole moment analysis revealed a direct relationship between the magnitude and frequency of the dipole moment and the strength and frequency of the external electric field. The type of electric field also played a role, with pulsed electric fields leading to larger average values of RMSD and RMSF for the whole protein. Additionally, the secondary structure analysis showed simultaneous transitions of alpha-helix segments to turns or random coils in a pulsed electric field, while different characteristic times were observed in an oscillating electric field. The study also demonstrated that proteins with fewer charged residues or more residues forming alpha-helical structures exhibited higher conformational stability. These findings have important theoretical implications for understanding the effect of frequency and expression form of external electric fields on conformational changes in all-alpha proteins with charged residues and provide guidance for potential applications.
Article
Engineering, Chemical
Binqi Rao, Gongqin Wang, Peng Xu
Summary: This paper provides a comprehensive review of recent advances in the dewatering and drying of sewage sludge. It covers factors influencing dewatering, conditioning methods to improve performance, and different dewatering and drying technologies. This research is significant for reducing sludge volume, minimizing pollution risks, and improving treatment efficiency.
Article
Polymer Science
Dongqing Shao, Qun Zhang, Peng Xu, Zhouting Jiang
Summary: The effect of temperature and salt solution on the structural characteristics of protein 1BBL was studied using molecular dynamics simulations. Non-bonded energy and structural stability of the protein in salt solutions with varying concentrations and temperatures were investigated. The study demonstrated that the electrostatic potential energy and van der Waals energy of the system changed in opposite directions under the influence of the external environment, with the former exhibiting more significant changes. Structural parameters, such as root mean square deviation and radius of gyration, initially increased and then decreased with increasing salt concentration. The protein exhibited a loose and less stable structure when immersed in a monovalent solution with a salt concentration of 0.8 mol/L. Furthermore, the salt concentration corresponding to the highest structural parameters in the monovalent solution was twice that in the divalent solution. It was concluded that the protein had a compact and stable structure when immersed in salt solutions with a high concentration of 2.3 mol/L. Analysis of root mean square deviation and root mean square fluctuation also revealed that structural stability and chain flexibility were strongly influenced by temperature. These findings contribute to a better understanding of the structural characteristics of proteins in salt solutions with varying concentrations and temperatures.
Article
Computer Science, Interdisciplinary Applications
Ke Chen, Xuzhen He, Fayun Liang, Daichao Sheng
Summary: Estimating capillary pressure's contribution to effective stress is essential for studying mechanical and hydraulic behavior of unsaturated soils. Based on experiments, we find that degree of saturation (Sr) is a better variable than matric suction (s) for modeling Bishop's effective stress parameter (chi). We introduce wet area fraction as an alternative to chi, considering the influence of hydraulic hysteresis and pore size distribution on shear strength through the soil water retention curve (SWRC). This model requires soil material parameters in the reference state and can predict strength characteristics in different mechanical or hydraulic states.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Engineering, Multidisciplinary
Lianlian Xu, Yao Xu, Hailin Gu, Shuxia Qiu, Arun S. S. Mujumdar, Peng Xu
Summary: Inspired by natural bifurcating structures, tree-like microchannels have been utilized for microelectronics cooling. The thermal-hydraulic performance of a flat-plate tree-like microchannel is investigated through the optimization of successive branching ratios based on flow resistance minimization. The study reveals that the optimal successive diameter ratio follows Murray's law and the optimal successive length ratio follows the power law 2(-2/3). A mathematical model is developed for convection in a disc-shaped heat sink with a self-affine rough surface. The optimized flat-plate tree-like microchannel demonstrates enhanced thermal-hydraulic performance and sheds light on the design of micro-channel heat sinks and flow channels in cooling applications.
ENGINEERING APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS
(2023)
Article
Chemistry, Physical
Chao Peng, Hailin Gu, Guangxue Zhang, Kun Luo, Peng Xu, Song Lv, Qiyao Zhang, Guobiao Chen
Summary: A novel cooling channel with dimple structures is designed and a three-dimensional PEMFC numerical model is established in this paper. Comparing to the conventional channels, the dimpled channel exhibits a 10% higher heat transfer performance and almost 13% lower pressure loss. The optimization of dimple structure parameters based on uniformity temperature index and heat transfer evaluation criteria is carried out, and it is recommended to use a diameter-to-depth ratio of 4 when the dimple diameter is less than 0.80 mm. The clock-wise vortex observed inside the dimple is considered as the main factor affecting heat exchange. This study will contribute to the design of cooling channels for high-power density PEMFCs in the future.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Biochemistry & Molecular Biology
Qiaoling Song, Zhenan Wu, Chenghao Jin, Zhichao Yu, Peng Xu, Zhouting Jiang
Summary: The effect of the ratio and consecutive number of hydrophobic residues on the structure of protein chains was investigated by molecular dynamics (MD) simulation. The results showed that proteins with higher ratios or larger numbers of consecutive hydrophobic residues exhibit more oriented and compact structures at low temperatures, leading to the formation of specific ordered structures.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Engineering, Chemical
Shuxia Qiu, Shengjun Xu, Binqi Rao, Arun S. Mujumdar, Peng Xu
Summary: This study presents a mathematical model for the hot air impingement drying of unsaturated porous materials and validates the model with experimental data. By analyzing the relationship between mesoscopic pore structures and macroscopic heat and mass transfer properties, the study provides useful guidance for improving the efficiency of impingement drying of porous materials.
JOURNAL OF FOOD ENGINEERING
(2022)
Article
Chemistry, Physical
Yao Xu, Lianlian Xu, Shuxia Qiu, Zhouting Jiang, Binqi Rao, Peng Xu
Summary: In this paper, a novel pore-scale model based on the equilateral triangle representative unit cell (RUC) and capillary bundle model is developed to understand the fluid flow through anisotropic fibrous porous material. The model considers factors such as fiber column size, porosity, and fractal dimensions, and provides an effective through-plane permeability prediction.
Article
Mathematics, Interdisciplinary Applications
Peng Xu, Jialiang Wang, Yao Xu, Fen Qiao, Zhouting Jiang, Binqi Rao, Shuxia Qiu
Summary: In this paper, a fractal Monte Carlo method (FMCM) is developed to reconstruct the random microstructure of fibrous porous material based on the fractal scaling laws of fiber columns. The effectiveness of the FMCM reconstruction is demonstrated by calculating the two-point correlation function of the reconstructed fibrous material. The finite element method is used to simulate the single-phase fluid flow through the reconstructed random fibrous porous material, and the predicted permeability agrees well with available empirical formulas.
FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY
(2023)
Article
Engineering, Environmental
Chuanrui Xu, Yao Xu, Jialiang Wang, Shuxia Qiu, Binqi Rao, Peng Xu
Summary: In this study, the sludge microstructure was measured and quantitatively characterized using fractal geometry. A new pore-scale physical model for the electroosmotic flow through sludge porous media was developed based on the EDL theory, and the analytical expressions for the electroosmotic flow rate and permeability coefficient were determined. The results show that the electroosmotic flow rate of sludge porous media depends on the sludge microstructure, and the electroosmotic permeability coefficient increases with an increase in porosity.
JOURNAL OF ENVIRONMENTAL ENGINEERING
(2023)
Article
Engineering, Civil
Ke Chen, Chen Wang, Fayun Liang
Summary: This paper presents a fractal-based hydraulic model that accurately describes the evolution of soil water characteristics and hydraulic conductivity during soil deformation.
JOURNAL OF HYDROLOGY
(2023)
Article
Energy & Fuels
Peng Xu, Jin Meng, Jialiang Wang, Boming Yu, Shuxia Qiu
Summary: A novel pore-scale physical model for effective thermal conductivity (ETC) of multiscale unsaturated porous media is developed, which shows acceptable agreement with experimental results. It is found that increasing tortuosity leads to higher thermal resistance and reduced ETC, while rough surfaces and Knudsen effect enhance and reduce ETC, respectively.
Article
Mathematics, Interdisciplinary Applications
Cheng Li, Yao Xu, Zhouting Jiang, Boming Yu, Peng Xu
Summary: A fractal pore-scale model with capillary bundle is used to investigate fluid flow, heat conduction, and gas diffusion in saturated porous material, and calculate conductivity properties. The results demonstrate the correlation between conductivity properties and changes in pore structure, which is validated through experiments and numerical simulations. This mapping method offers a new approach to understanding transport processes in porous materials.
FRACTAL AND FRACTIONAL
(2022)
