Simulation Method Research Articles

Experimental and Numerical Investigation on Group Anchor Performance of Wooden Bolts in Rammed Earthen Sites

ABSTRACT Challenges remain in understanding the interaction mechanisms and influencing factors of multi-anchor systems. To investigate this matter, this study conducted nine full-scale model experiments examining the pulling resistance and failure modes of wood bolts embedded in rammed earth. These experiments varied bolt numbers (2, 3, 4), spacings (500 mm, 1000 mm, 1500 mm), and embedment depths (200 mm, 300 mm, 400 mm). Key factors and their levels for the group anchoring effect in the model tests were determined through orthogonal analysis. Among these factors, embedment depth exerted the most significant influence on pulling resistance, followed by bolt spacing and number. Furthermore, a numerical simulation method for wooden anchor group systems was developed using the “contact surface” element in FLAC 3D finite difference simulation software. This method considered factors such as bolt number, spacing, edges, embedment depth, and the layered nature of the compacted soil. It analyzed stress distribution and transmission laws across various interfaces within the anchoring system and the compacted soil, thereby supplementing and expanding upon the findings of the model experiments. These findings enhance understanding of the complex interplay between multi-anchor systems and soil, providing a scientific foundation for analyzing mechanical behavior in similar anchoring applications.

Donnan equilibrium in charged slit-pores from a hybrid nonequilibrium molecular dynamics/Monte Carlo method with ions and solvent exchange.

Ion partitioning between different compartments (e.g., a porous material and a bulk solution reservoir), known as Donnan equilibrium, plays a fundamental role in various contexts such as energy, environment, or water treatment. The linearized Poisson-Boltzmann (PB) equation, capturing the thermal motion of the ions with mean-field electrostatic interactions, is practically useful to understand and predict ion partitioning, despite its limited applicability to conditions of low salt concentrations and surface charge densities. Here, we investigate the Donnan equilibrium of coarse-grained dilute electrolytes confined in charged slit-pores in equilibrium with a reservoir of ions and solvent. We introduce and use an extension to confined systems of a recently developed hybrid nonequilibrium molecular dynamics/grand canonical Monte Carlo simulation method ("H4D"), which enhances the efficiency of solvent and ion-pair exchange via a fourth spatial dimension. We show that the validity range of linearized PB theory to predict the Donnan equilibrium of dilute electrolytes can be extended to highly charged pores by simply considering renormalized surface charge densities. We compare with simulations of implicit solvent models of electrolytes and show that in the low salt concentrations and thin electric double layer limit considered here, an explicit solvent has a limited effect on the Donnan equilibrium and that the main limitations of the analytical predictions are not due to the breakdown of the mean-field description but rather to the charge renormalization approximation, because it only focuses on the behavior far from the surfaces.

Muonium state exchange dynamics in n -type GaAs

Muonium (Mu), a pseudoisotope of hydrogen with a positively charged muon in place of the proton, takes the form Mu+,0,− (like isolated hydrogen, i.e., H+,0,−) in semiconductors. The specifics of the charge state depend on the local electronic environment of the host. After initial muon implantation, generated Mu centers interact with free charge carriers and electronic spins, transition between sites, and form a dynamic network of state exchange. We identified the model of Mu dynamics in n-type GaAs using the density matrix simulation method and photoexcited muon spin spectroscopy technique. Fitting to the dark and illuminated μSR data provided transition rates between Mu states, revealing the underlying mechanisms at play between the Mu centers (cf. isolated H) and the host. Deduced capture/scattering cross sections of the Mu states reflected the microscopic dynamics of Mu. Illumination studies enabled us to measure interactions between Mu and minority carriers, which would be unavailable in dark measurements without heating. The methodology developed in this study may be applied to other semiconductor systems for a deeper understanding of the Mu state exchange dynamics. Published by the American Physical Society 2024

Street Community-Level Urban Flood Risk Assessment Based on Numerical Simulation

Urban waterlogging is a serious urban disaster, which brings huge losses to the social economy and environment of the city. As an important means of urban rainfall inundation analysis, numerical simulation plays an important role in promoting the risk assessment of urban waterlogging. Scientific and accurate assessment of waterlogging disaster losses is of scientific significance for the formulation of disaster prevention and mitigation measures and the guidance of post-disaster recovery and reconstruction. In this study, the SCS-CN hydrological model and GIS coupling numerical simulation method were used to simulate the inundation of urban waterlogging under four different rainfall return periods and to realize the visualization of the inundation range and waterlogging depth in Zhengzhou. At the same time, based on the numerical simulation results, the building is used as the basic assessment unit to construct a refined assessment framework for urban waterlogging risk at the street community level based on hazard, exposure, and vulnerability analysis. The refined risk assessment results have an important reference value for optimizing the working ideas of waterlogging control and providing a reference for local management departments to effectively deal with waterlogging disasters.

Analysis of Fracturing Expansion Law of Shale Reservoir by Supercritical CO2 Fracturing and Mechanism Revealing

The rapid expansion of reservoir fractures and the enlargement of the area affected by working fluids can be accomplished solely through fracturing operations of oilfield working fluids in geological reservoirs. Supercritical CO2 is regarded as an ideal medium for shale reservoir fracturing owing to the inherent advantages of environmental friendliness, excellent capacity, and high stability. However, CO2 gas channeling and complex propagation of fractures in shale reservoirs hindered the commercialization of Supercritical CO2 fracturing technology. Herein, a simulation method for Supercritical CO2 fracturing based on cohesive force units is proposed to investigate the crack propagation behavior of CO2 fracturing technology under different construction parameters. Furthermore, the shale fracture propagation mechanism of Supercritical CO2 fracturing fluid is elucidated. The results indicated that the propagation ability of reservoir fractures and Mises stress are influenced by the fracturing fluid viscosity, fracturing azimuth angle, and reservoir conditions (temperature and pressure). An azimuth angle of 30° can achieve a maximum Mises stress of 3.213 × 107 Pa and a crack width of 1.669 × 10−2 m. However, an apparent viscosity of 14 × 10−6 Pa·s results in a crack width of only 2.227 × 10−2 m and a maximum Mises stress of 4.459 × 107 Pa. Additionally, a weaker fracture propagation ability and reduced Mises stress are exhibited at the fracturing fluid injection rate. As a straightforward model to synergistically investigate the fracture propagation behavior of shale reservoirs, this work provides new insights and strategies for the efficient extraction of shale reservoirs.

Movement characteristics of coal powders at bottom of coalbed methane well under jet flow

AbstractThe removal and discharge of coal powders from coalbed methane wellbore is the key to maintaining continuous production. For this reason, based on the submerged jet theory, the force and migration starting conditions of coal powder particles deposited at the bottom of the coalbed methane well are analyzed by analyzing the cohesiveness of coal powders, and a model for the starting and migration of coal powders at the bottom of the well under submerged jet conditions is established; Considering the adhesion between coal dust, the adhesion coefficient is used to characterize the adhesion between particles, a mechanical model of coal dust particles deposited at the bottom of the well is established, and the corresponding calculation formula for the outlet flow rate of the coal dust cleaning nozzle is derived. The fluid mechanics parameters of the bottom of the well coal dust cleaning under different conditions are obtained, and the numerical simulation method is used to simulate the whole process of jet flushing of the bottom of the well coal dust deposited, and the effect of the bottom of the well jet flushing of coal dust deposits is analyzed, providing a theoretical basis for the bottom of the well coal dust flushing process.

Assessing the Efficiency of Fully Two-Dimensional Hydraulic HEC-RAS Models in Rivers of Cyprus

Floods are among the most widespread and recurrent natural disasters globally. In the European region, climate change leads to an increase in the incidence and intensity of flooding. For effective management of the phenomenon, the European Union instituted Directive 2007/60/EC for the assessment and management of flood risks in order to reduce the negative consequences of flooding on human health, economic activities, the environment, and cultural heritage. Cyprus, as a member of the European Union, had to comply with the provisions of the directive. Within the second implementation of the directive, combined 1D/2D hydraulic models were conducted. These data served as a benchmark for the present research, in which the differences in the inundated area, depths, and simulation time are investigated using a full 2D hydraulic simulation. The present research examines two Areas of Potentially Significant Flood Risk, one in an urban and one in a rural area. Overall, the proposed 2D methodology was found to represent inundated areas to a good extent with almost zero deviation in comparison to the 1D/2D method. This study demonstrated the adequacy of the 2D hydraulic simulation method, which offers greater flexibility in modeling a variety of hydraulic scenarios, enabling planning and flood risk management that is vital for protecting communities, infrastructure and the environment from the devastating impacts of floods.

Low-Carbon Supply Chain Decision-Making and CSR Strategy Evolution Analysis Considering Heterogeneous Consumer Preferences

Decision-making regarding the low-carbon supply chain, considering corporate social responsibility (CSR) and the heterogeneous preferences of consumers, has become an urgent topic to be explored. This paper explores the decision-making problem of a low-carbon supply chain considering the heterogeneous preferences of consumers under different CSR situations, analyzes the influence of important parameters on each equilibrium solution, compares the size relationship of each equilibrium solution under different CSR situations, and verifies the conclusions obtained through numerical simulation. Then, based on the obtained equilibrium solution, a CSR evolutionary game model of the low-carbon supply chain is constructed, and the evolutionary stability strategies of the two sides on the CSR game are solved. Finally, the evolutionary trajectory of the game system is intuitively presented using a simulation method, and the influence of the main parameters on the evolutionary trends of the two sides is analyzed. The findings are as follows: (1) When both manufacturers and retailers undertake CSR, the retail price and wholesale price are their lowest, while carbon emission reduction, total market demand, manufacturer utility, retailer utility, and supply chain total utility are the highest. (2) When a company undertakes CSR, carbon emission reduction, total market demand, manufacturer utility, retailer utility, and supply chain total utility all increase with the increase in the CSR degree of the company and the ratio of the potential scale of low-carbon consumers to the potential scale of ordinary consumers. (3) The evolutionary stability strategy for both manufacturers and retailers is to undertake CSR. In addition, the initial proportion of manufacturers and retailers that undertake CSR, the low-carbon preference of low-carbon consumers, and the increase in the ratio of the potential scale of low-carbon consumers to the potential scale of ordinary consumers can encourage both members of the supply chain to undertake CSR.

Fractal evolution characteristics of fracture meso-damage in uniaxial compression rock masses using bonded block model

With regard to deep mining in metal mines, an investigation into the failure mode of deep fractured rock masses and their corresponding acoustic emission signal characteristics is conducted via uniaxial compression tests. Subsequently, a fractal damage renormalization group mechanical model is developed to explain the behavior of those fractured rock masses. Employing the bonded block model (BBM) numerical simulation method, fracture process in synthetic rock samples is analyzed, thereby validating the efficacy of the mechanical model. The numerical simulations highlight the critical role of fractures expansion in underlying the deterioration of rock mass strength. As the peak load decreases, the fracture fractal dimension increases, leading to a significant 14.2% reduction in compressive strength accompanied by an approximate 8.7% rise in average fracture fractal dimension. A comparative analysis of tetrahedral and voronoi block synthetic rock samples reveals the tetrahedral block samples exhibit a superior ability to depict the fracture behavior of fractured rock masses. Specifically, they offer a more accurate simulation of acoustic emission characteristics and failure modes. Furthermore, variations in the fracture fractal dimension with respect to the hole defect’s position are observed, with the maximum value occurring along the vertical axis of the hole defect. This observation underscores the potential utility of visually monitoring deep rock fracture dynamics as an effective mean for quantitatively evaluating fracture damage and strength degradation in deep rock formations.

Energy performance and pressure fluctuation in multi-stage centrifugal pump with floating impellers under various axial oscillation frequencies

A novel multi-stage centrifugal pump with floating impellers is gaining traction in energy systems because it easily links stages in series for varying high head requirements. However, the axial oscillation frequency of the floating impeller introduces uncertainties in the pump's energy performance and pressure fluctuation. To address these issues, a comprehensive analysis of multi-stage centrifugal pumps was conducted, utilizing a computational fluid dynamics simulation method that incorporats dynamic mesh and multiple reference frame techniques, validated through three experimental trials. The findings show that average head coefficient and average efficiency are not significantly affected by the axial oscillation of impeller, but that pressure fluctuations, efficiency, and head coefficient all show periodic variations that are connected to the frequency of impeller oscillation. The amplitude of variations in the head coefficient and efficiency could increase by as much as 112.3 % and 172.4 %, respectively, under the influence of impeller oscillations, thereby heightening the instability of pump operation. Trigonometric functions for the energy performance during impeller oscillations are proposed to facilitate rapid assessment of pump stability. This study offers valuable insights into the unsteady characteristics of novel multi-stage centrifugal pumps and serves as a reference for further understanding their dynamic behavior.

Ground-to-air aircraft infrared image deblurring based on imaging degradation simulation

The issue of infrared image deblurring has been a significant concern. However, in some specific scenes, the current mainstream deblurring algorithms based on optimization or deep learning fail to provide satisfactory results. Aiming to address the ineffectiveness of deep learning methods due to the low-cost datasets' unavailability for specific scenes, we innovatively propose a relatively simple full-chain imaging degradation simulation method using ground-to-air aircraft infrared imaging scene as an example, which considers the effects of blur and noise caused by the atmosphere, imaging system, target motion and detector. Through this method, we could generate abundant blur-clear image pairs by altering various parameters. To enhance the neural network’s generalization ability and the deblurring performance in the specific scenes, we employ a two-step approach: pretraining on the public GoPro dataset and subsequent finetuning on the simulation dataset. After testing on the simulation dataset and some real-world images, we have discovered the importance of selecting a pretraining dataset that closely matches the scene degradation mode. Additionally, regardless of whether the model is pre-trained on the UIRD or GoPro dataset, there are significant enhancements in the deblurring effect following finetuning with our constructed simulation dataset. In summary, compared to the traditional deconvolution methods and the methods trained on a general dataset, our approach not only exhibits superior deblurring capabilities but also effectively mitigates noise and prevents the occurrence of artifactual textures such as ringing artifact.

An improved delayed detached-eddy study on the aerodynamic braking technique based on blunting the streamlined section of the high-speed train

This paper utilizes the improved delayed detached-eddy simulation method to investigate an aerodynamic braking technique involving blunting the streamlined portion of a high-speed train (HST) at Re = 5.0 × 105. The accuracy of the numerical simulation method was validated through reduced-scale wind tunnel experiments at the same Reynolds number level. The study compares aerodynamic drag, pressure distribution, boundary layer, and wake flow characteristics between the original configuration and the braking configuration of the HST. Additionally, the impact of aerodynamic braking plates on the flow characteristics around the key components of the HST has also been discussed. The results indicate a significant increase in the pressure drag experienced by the HST with the application of aerodynamic braking plates to its streamlined sections, while there is a slight decrease in viscous drag. This leads to a remarkable 235.4% rise in the overall aerodynamic drag of the entire HST. The aerodynamic braking plates also have a substantial impact on the turbulent wake flow topology, significantly increasing turbulence levels in the near-wake region. Furthermore, the implementation of aerodynamic braking plates may affect pantograph current collection by significantly altering stream-wise and vertical velocity components, notably increasing velocity fluctuation around the contact position between the pantograph and power supply lines.

Comprehensive study of Kinetic Trajectory Simulation method for multi-component magnetized plasma-wall interaction process

For a wide range of plasma applications across diverse fields, a comprehensive understanding of the plasma-wall interaction mechanism is indispensable due to its inherent connection with confined plasma. This work compilation delves into the Kinetic Trajectory Simulation (KTS) method for the interaction of multi-component magnetized plasma with wall, specifically focusing on its implications for the tungsten wall sputtering model. In the evolution of the 1d3v (one dimensional spatial coordinates and three dimensional velocity coordinates) KTS method, the coupled set of kinetic equations has been solved under specified boundary conditions which yields results of higher accuracy. At the particle injection boundary, we have assumed the velocity distribution function of particle species to be cut-off Maxwellians, meeting essential requirements for plasma-wall transition processes: quasineutrality, sheath edge singularity, continuity of macroscopic fluid variables, and the kinetic Bohm sheath condition. The kinetic Bohm sheath condition, a fundamental criterion for plasma sheath formation, is extended for multi-component plasmas, accounting for the cut-off Maxwellian distribution of negatively charged particles. A comparative study of the kinetic Bohm sheath condition for cut-off and Boltzmann distributions reveals a deviation of less than 2.0% in magnitude. The concentration ratio of positive or negative ion species and the presheath side electron temperature influence various plasma-wall transition characteristics, including wall potential, Debye sheath thickness, particle densities, potential distribution, particle fluxes towards the surface, particle drift velocity, phase-space trajectory evolution, and physical sputtering of the tungsten surface. Although lighter ions possess higher energy when striking the surface, the physical sputtering yield of the tungsten surface is greater for heavier ions due to their lower threshold energy and larger collision cross-section. Furthermore, a comparative study of plasma-wall transition properties using kinetic and fluid approaches demonstrates qualitative similarities, with a notable deviation of approximately 4.0% in the magnitude in the vicinity of the material surface.

Impact of surface-active ionic solutions on the structure and function of laccase from trametes versicolor: Insights from molecular dynamics simulations

Many protein-ionic liquid investigations have examined laccase interactions. Laccases are a class of poly-copper oxidoreductases that retain significant biotechnological relevance owing to their notable oxidative capabilities and their application in the elimination of synthetic dyes, phenolic compounds, insecticides, and various other substances. This study investigates the impact of surface active ionic liquids (SAILs), namely, decyltrimethylammonium bromide [N10111][Br] and 1-decyl-3-methylimidazolium chloride [C10mim][Cl] as cationic surfactant ionic liquids and cholinium decanoate [Chl][Dec], an anionic surfactant ionic liquid, on the structure and function of laccase from the fungus Trametes versicolor (TvL) by the molecular dynamics (MD) simulation method. In summary, this study showed that laccase solvent-accessible surface area increased in the ionic liquid [Chl][Dec] while it decreased in the other two ionic liquids. Interestingly, [Chl][Dec] ionic liquid components formed hydrogen bonds with laccase, while [N10111][Br] and [C10mim][Cl] components were unable to form hydrogen bonds with laccase. The quantity of hydrogen bonds formed between water molecules and the enzyme was also diminished in the presence of [Chl][Dec] in comparison to the other two ionic liquids. especially at a concentration of 250 mM. In 250 mM concentrations of [N10111][Br] and [C10mim][Cl], clusters of long-chain cations are likely to form near the copper T1 site. However, even at low [Chl][Dec] concentrations, long [Dec]- chains were observed to penetrate the enzyme near the copper T1 site, and at 250 mM [Chl][Dec], a large cluster of anions occupied the opening of the active site. The results of the analysis also show that the interaction between the [Dec]- anion and the enzyme is stronger than the interaction between [N10111]+ and [C10mim]+ with laccase; in addition, the [Dec]- anion, compared to [Br]- and [Cl]- has a much greater tendency to bind with the enzyme residues.

A multiblock (MIB) finite element method for accurate and efficient blood flow simulation

We present an efficient and accurate immersed boundary (IB) finite element (FE) method for internal flow problems with complex geometries (e.g. blood flow in the vascular system). In this study, we use a voxelized flow domain (discretized with hexahedral and tetrahedral elements) instead of a box domain, which is frequently used in IB methods. We highlight the applicability and efficiency of the proposed method in generating the flow domain mesh and removing unnecessary portions of the domain, compared to the standard IB methods that rely on a full Cartesian mesh. Our approach is attractive for internal flow problems that use IB methods. The proposed method accurately satisfies the boundary conditions on the immersed object using velocity and pressure correction procedures. The velocity correction applies implicitly such that the velocity on the immersed boundary (Lagrangian points) interpolated from the corrected velocity values computed on the mesh nodes (Eulerian nodes) accurately satisfies the prescribed velocity boundary conditions. The proposed method utilizes the well-established incremental pressure correction scheme (IPCS) FE solver, and the boundary condition-enforced IB (BCE-IB) method to numerically solve the transient, incompressible Navier-Stokes (NS) flow equations. We verify the accuracy of our numerical method using the analytical solution for the Poiseuille flow in a cylinder, and the available experimental data (laser Doppler velocimetry) for the flow in a three-dimensional 90° angle tube bend. We further examine the accuracy and applicability of the proposed method by considering flow within complex geometries, such as blood flow in aneurysmal vessels and the aorta, flow configurations that would otherwise be difficult to solve by most IB methods. Our method offers high accuracy, as demonstrated by the verification examples, and high applicability, as demonstrated through the solution of blood flow within complex geometry. The proposed method is efficient, since it is as fast as the traditional finite element method used to solve the Navier–Stokes flow equations, with a small overhead (not more than 5%) due to the numerical solution of a linear system formulated for the IB method.

A Stochastic Iterative Peer-to-Peer Energy Market Clearing in Smart Energy Communities Considering Participation Priorities of Prosumers

The penetration of distributed energy resources (DERs) has changed the role of a consumer to a prosumer, i.e., producer and consumer. This new role provides the opportunity for peer-to-peer (P2P) energy trading. In this paper, a three-stage iterative framework is proposed to clear the price and quantity of trading in P2P markets while addressing price and DER uncertainties by the Monte Carlo simulation (MCS) method. Initially, bids and offers of customers are determined by implementing an advanced satisfaction-based home energy management system (HEMS) at each home. Subsequently, the market operator prioritizes bids and offers according to the amount of customers’ participation in the market. Finally, the P2P market is cleared by application of the alternating direction method of multipliers (ADMM), and the market clearing prices (MCPs) are determined. MCPs are used as a parameter to repeat the three stages, and the procedure is redone until the stopping rule is met. The proposed method's effectiveness has been investigated in communities with 8, 50, and 100 prosumers. Results indicate a 69.51% cost reduction in a smart energy community with 50 homes through P2P energy market participation. The proposed market clearing method is compared with the common mid-market rate (MMR) and Stackelberg game methods and demonstrates over 25% reduction in community costs.

Development of Node-centered finite-volume diffusion method on triangle mesh for detonation propagation simulation in insensitive high explosives

This study presents a numerical simulation of detonation waves in insensitive high explosives (IHE). A direct numerical simulation (DNS) method of detonation waves propagation was developed. It solves two-dimensional reactive Euler equations by using a semi-discrete node-centered finite-volume (NCFV) scheme on triangle mesh. Employing ZND model analytical solution as the initial condition, the upper and lower boundary conditions were designed as local sonic equilibrium conditions. The DNS method was validated using steady detonation wave propagation experimental results for tri-amino-tri-nitro-benzene (TATB) based explosives. The two-dimensional steady detonation propagation of the circular arc experiments was completed using a non-embedded technique (electric and optical fibre probe velocimetry). The comparison results demonstrate that the numerical method can provide a good prediction of the pseudo-steady-state detonation wave front propagation and the angular speed.

Study of Simulation Method of Porosity and Permeability Parameters of Salt Deposition Reservoir Based on Phase Equilibrium Calculation

Study of Simulation Method of Porosity and Permeability Parameters of Salt Deposition Reservoir Based on Phase Equilibrium Calculation

Stochastic Characteristic Simulation Method of Inertial Devices Based on Allan Variance Matching

Stochastic Characteristic Simulation Method of Inertial Devices Based on Allan Variance Matching

An Improved Numerical Simulation Method for Rockbolt Fracture and Its Application in Deep Extra-Thick Coal Seam Roadways

An Improved Numerical Simulation Method for Rockbolt Fracture and Its Application in Deep Extra-Thick Coal Seam Roadways