Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is sti...Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs,as well as the stress interference patterns between fractures.This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluidsolid coupling discrete element method(DEM),and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance.The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30%and that fracture pressure increases with saturation.The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance.The distribution uniformity index(DUI)reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time,with fracturing efficiency depending on the spacing between injection points and the distance between wells.This work may provide reference for the commercial exploitation of natural gas hydrates.展开更多
Nonuniform track support and differential settlements are commonly observed in bridge approaches where the ballast layer can develop gaps at crosstie-ballast interfaces often referred to as a hanging crosstie conditio...Nonuniform track support and differential settlements are commonly observed in bridge approaches where the ballast layer can develop gaps at crosstie-ballast interfaces often referred to as a hanging crosstie condition.Hanging crossties usually yield unfavorable dynamic effects such as higher wheel loads,which negatively impact the serviceability and safety of railway operations.Hence,a better understanding of the mechanisms that cause hanging crossties and their effects on the ballast layer load-deformation characteristics is necessary.Since the ballast layer is a particulate medium,the discrete element method(DEM),which simulates ballast particle interactions individually,is ideal to explore the interparticle contact forces and ballast movements under dynamic wheel loading.Accurate representations of the dynamic loads from the train and track superstructure are needed for high-fidelity DEM modeling.This paper introduces an integrated modeling approach,which couples a single-crosstie DEM ballast model with a train–track–bridge(TTB)model using a proportional–integral–derivative control loop.The TTB–DEM model was validated with field measurements,and the coupled model calculates similar crosstie displacements as the TTB model.The TTB–DEM provided new insights into the ballast particle-scale behavior,which the TTB model alone cannot explore.The TTB–DEM coupling approach identified detrimental effects of hanging crossties on adjacent crossties,which were found to experience drastic vibrations and large ballast contact force concentrations.展开更多
Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression an...Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression and permeability tests to investigate the mechanical and seepage properties of tight sandstone.A digital core of tight sandstone was built using Computed Tomography(CT)scanning,which was divided into matrix and pore phases by a pore equivalent diameter threshold.A fluid-solid coupling model was established to investigate the seepage characteristics at micro-scale.The results showed that increasing the confining pressure decreased porosity,permeability,and flow velocity,with the pore phase becoming the dominant seepage channel.Cracks and large pores closed first under increasing pressure,resulted in a steep drop in permeability.However,permeability slightly decreased under high confining pressure,which followed a first-order exponential function.Flow velocity increased with seepage pressure.And the damage mainly occurred in stress-concentration regions under low seepage pressure.Seepage behavior followed linear Darcy flow,the damage emerged at seepage entrances under high pressure,which decreased rock elastic modulus and significantly increased permeability.展开更多
A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution t...A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution terms between the cold fluid and the hot rock are derived.Heat transfer obeys Fourier's law,and porosity is used to relate the thermodynamic parameters of the fracture and matrix domains.The net pressure difference between the fracture and the matrix is neglected,and thus the fluid flow is modeled by the unified fluid-governing equations.The evolution equations of porosity and Biot's coefficient during hydraulic fracturing are derived from their definitions.The effect of coal cleats is considered and modeled by Voronoi polygons,and this approach is shown to have high accuracy.The accuracy of the proposed model is verified by two sets of fracturing experiments in multilayer coal seams.Subsequently,the differences in fracture morphology,fluid pressure response,and fluid pressure distribution between direct fracturing of coal seams and indirect fracturing of shale interlayers are explored,and the effects of the cluster number and cluster spacing on fracture morphology for multi-cluster fracturing are also examined.The numerical results show that the proposed model is expected to be a powerful tool for the fracturing design and optimization of deep coalbed methane.展开更多
In the context of global warming and intensified human activities,glacier instability in plateau regions has increased,and glacier debris flows have become active,which poses a significant threat to the lives and prop...In the context of global warming and intensified human activities,glacier instability in plateau regions has increased,and glacier debris flows have become active,which poses a significant threat to the lives and property of people and socioeconomic development.The mass movement process of glacier debris flows is extremely complex,so this paper uses the 2018 Sedongpu glacier debris flow event on the Qinghai-Tibet Plateau as an example and applies a numerical simulation method to invert the whole process of mass movement.In view of the interaction between phases in the process of motion,we use the fluid-solid coupling method to describe the mass movement.The granular-flow model and drift-flux model are employed in FLOW3D software to study the mass movement process of glacier debris flows and explore their dynamic characteristics.The results indicate that the glacier debris flow lasted for 700 s,and the movement process was roughly divided into four stages,including initiation,scraping,surging and deposition;the depositional characteristics calculated by the fluid-solid coupling model are consistent with the actual survey results and have good reliability;strong erosion occurs during the mass movement,the clear volume amplification effect,and the first wave climbs 17.8 m across the slope.The fluid-solid coupling method can better simulate glacier debris flows in plateau regions,which is helpful for the study of the mechanism and dynamic characteristics of such disasters.展开更多
Deep underground excavation causes considerable unloading effects,leading to a pronounced bias pressure phenomenon.The deformation and seepage characteristics of rock masses under different gas and confining pressures...Deep underground excavation causes considerable unloading effects,leading to a pronounced bias pressure phenomenon.The deformation and seepage characteristics of rock masses under different gas and confining pressures were investigated via triaxial loading and unloading seepage tests.When the influential coefficient of effective confining pressure(β)is less than 0.065,the seepage force considerably weakens the strength of fractured rock masses.Conversely,whenβis greater than 0.065,the opposite is true.Moreover,the increase in the axial load leads to an increase in the precast fracture volumetric strain,which is the main reason for the increase in fracture permeability.This effect is particularly significant during the unloading stage.Based on the test results,a method for calculating the dynamic seepage evolution of rock masses,considering the effects of rock mass damage and fracture deformation,is introduced,and the effectiveness of the calculation is validated.The entire description of the seepage under loading and unloading was accomplished.The equivalent relationship between the lateral and normal stresses on fracture surfaces ranges from 0.001 to 0.1,showing an exponential variation between the lateral stress influence coefficient on normal deformation(χ)and seepage pressure.Before the failure of the rock mass,the seepage in the fractures was in a linear laminar flow state.However,after the failure,when the gas pressure reached 2 MPa,the flow state in the fractures transitioned to nonlinear laminar flow.The results are important for predicting hazardous gas leaks during deep underground engineering excavation.展开更多
Shallow water infrastructure needs to support increased activity on the shores of Semarang.This study chooses several pontoons because of their good stability,rolling motion,and more expansive space.A coupled simulati...Shallow water infrastructure needs to support increased activity on the shores of Semarang.This study chooses several pontoons because of their good stability,rolling motion,and more expansive space.A coupled simulation method consisting of hydrodynamic and structural calculations has been used to evaluate a catamaran pontoon’s motion and structural integrity.Four different space sizes are set for the pontoon system:5 m,5.5 m,6 m,and 6.5 m.The frequency domain shows that the pontoon space affects the RAO in wave periods ranging from 3 s to 5 s.At wave periods of 3 s,4 s,and 5 s,the pontoon space significantly affects the maximum motion and chain tension parameter values,which are evaluated via time domain simulation.The critical stress of the pontoon is shown at a wave period of 5 s for 5 m and 5.5 m of pontoon space,which shows that the stress can reach 248 MPa.展开更多
The Boussinesq equations,pivotal in the analysis of water wave dynamics,effectively model weakly nonlinear and long wave approximations.This study utilizes the complete discriminant system within a polynomial approach...The Boussinesq equations,pivotal in the analysis of water wave dynamics,effectively model weakly nonlinear and long wave approximations.This study utilizes the complete discriminant system within a polynomial approach to derive exact traveling wave solutions for the coupled Boussinesq equation.The solutions are articulated through soliton,trigonometric,rational,and Jacobi elliptic functions.Notably,the introduction of Jacobi elliptic function solutions for this model marks a pioneering advancement.Contour plots of the solutions obtained by assigning values to various parameters are generated and subsequently analyzed.The methodology proposed in this study offers a systematic means to tackle nonlinear partial differential equations in mathematical physics,thereby enhancing comprehension of the physical attributes and dynamics of water waves.展开更多
This paper introduces a bond-based peridynamics(BB-PD)algorithm for crack identification,integrating the Delaunay triangulation method to accurately identify the structural characteristics of threedimensional(3D)crack...This paper introduces a bond-based peridynamics(BB-PD)algorithm for crack identification,integrating the Delaunay triangulation method to accurately identify the structural characteristics of threedimensional(3D)cracks in rocks.A bond-based crack quantification standard is proposed to analyze the evolution of cracks of various sizes.A multi-attribute peridynamic model,developed using a multilayer algorithm,was employed to simulate the fracturing process of sandstone disks and semi-disks under varying temperatures,with the model calibrated and validated against experimental results.The simulation results show that temperature induces nonlinear degradation in the tensile strength and fracture toughness of sandstone,with 500℃ identified as the threshold temperature.Thermal cracks exhibit varying degrees of influence on Mode I cracks across different temperature ranges.Thermal damage significantly promotes the initiation and propagation of Mode I cracks in sandstone,thereby reducing its tensile strength and fracture toughness.Under applied loads,crack propagation in sandstone predominantly occurs during the failure stage,characterized by the rapid growth of longer cracks and a slow increase or reduction in shorter cracks.展开更多
Arsenic speciation in freshwater fish is crucial for providing meaningful consumption guidelines that allow the public to make informed decisions regarding its consumption.While marine fish have attractedmuch research...Arsenic speciation in freshwater fish is crucial for providing meaningful consumption guidelines that allow the public to make informed decisions regarding its consumption.While marine fish have attractedmuch research interest due to their higher arsenic content,research on freshwater fish is limited due to the challenges in quantifying and identifying arsenic species present at trace levels.We describe here a sensitivemethod and its application to the quantification of arsenic species in freshwater fish.Arsenic species from fish tissues were extracted using a methanol/water mixture(1:1 vol.ratio)and ultrasound sonication.Anion-exchange high-performance liquid chromatography(HPLC)enabled separation of arsenobetaine(AsB),inorganic arsenite(iAs^(Ⅲ)),dimethylarsinic acid(DMA),monomethylarsonic acid(MMA),inorganic arsenate(iAs^(Ⅴ)),and three new arsenic species.Inductively coupled plasma mass spectrometry(ICPMS)provided highly sensitive and specific detection of arsenic.A limit of detection of 0.25μg/kg(wet weight fish tissue)was achieved for the five target arsenic species:AsB,iAs^(Ⅲ),DMA,MMA,and iAs^(Ⅴ).A series of experimentswere conducted to ensure the accuracy and validity of the analytical method.The method was successfully applied to the determination of arsenic species in lakewhitefish,northern pike,and walleye,with AsB,DMA,and iAs^(Ⅴ) being frequently detected.Three new arsenic species were detected,but their chromatographic retention times did not match with those of any available arsenic standards.Future research is necessary to elucidate the identity of these new arsenic species detected in freshwater fish.展开更多
Spurious forces are a significant challenge for multi-scale methods,e.g.,the coupled atomistic/discrete dislocation(CADD)method.The assumption of isotropic matter in the continuum domain is a critical factor leading t...Spurious forces are a significant challenge for multi-scale methods,e.g.,the coupled atomistic/discrete dislocation(CADD)method.The assumption of isotropic matter in the continuum domain is a critical factor leading to such forces.This study aims to minimize spurious forces,ensuring that atomic dislocations experience more precise forces from the continuum domain.The authors have already implemented this idea using a simplified and unrealistic slipping system.To create a comprehensive and realistic model,this paper considers all possible slip systems in the face center cubic(FCC)lattice structure,and derives the required relationships for the displacement fields.An anisotropic version of the three-dimensional CADD(CADD3D)method is presented,which generates the anisotropic displacement fields for the partial dislocations in all the twelve slip systems of the FCC lattice structure.These displacement fields are tested for the most probable slip systems of aluminum,nickel,and copper with different anisotropic levels.Implementing these anisotropic displacement fields significantly reduces the spurious forces on the slip systems of FCC materials.This improvement is particularly pronounced at greater distances from the interface and in more anisotropic materials.Furthermore,the anisotropic CADD3D method enhances the spurious stress difference between the slip systems,particularly for materials with higher anisotropy.展开更多
The properties of the magnetic mold in magnetic mold casting directly determine the quality of the final cast parts.In this study,the magnetic mold properties in magnetic mold casting,were studied utilizing a coupled ...The properties of the magnetic mold in magnetic mold casting directly determine the quality of the final cast parts.In this study,the magnetic mold properties in magnetic mold casting,were studied utilizing a coupled electromagnetic-structural method through numerical simulation.This study investigated key factors including equivalent stress,the distribution of tensile and compressive stresses,and the area ratio of tensile stress.It compared molds made entirely of magnetic materials with those made partially of magnetic materials.Simulation results indicate that as current increases from 4 A to 8 A,both the initial magnetic mold and the material-replaced magnetic mold initially show an increasing trend in equivalent stress,tensile-compressive stress,and the area ratio of tensile stress,peaking at 6 A before declining.After material replacement,the area ratio of tensile stress at 6 A decreases to 19.84%,representing a reduction of 29.72%.Magnetic molds comprising a combination of magnetic and non-magnetic materials exhibit sufficient strength and a reduced area ratio of tensile stress compared to those made entirely from magnetic materials.This study provides valuable insights for optimizing magnetic mold casting processes and offers practical guidance for advancing the application of magnetic molds.展开更多
42CrMo steel has the characteristics of high strength,high wear resistance,high impact resistance,and fatigue resistance.Therefore,drilling 42CrMo steel has always been a challenging task.The indexable drill bit has t...42CrMo steel has the characteristics of high strength,high wear resistance,high impact resistance,and fatigue resistance.Therefore,drilling 42CrMo steel has always been a challenging task.The indexable drill bit has the advantages of high processing efficiency and low processing cost and has been widely used in the field of aerospace hole processing.To better understand the machining mechanism of the indexable drill bit,this paper uses the Coupled EulerianLagrangian method(CEL)to simulate the three-dimensional drilling model for the first time.The simulation results of the drilling force obtained by the CEL method and Lagrangian method are compared with the experimental results.It is verified that the CEL method is easy to converge and can avoid the problem of program interruption caused by mesh distortion,and the CEL simulation value is more consistent with the actual value.Secondly,the simulation results of cutting force and blade cutting edge node temperature under different process parameters are extracted.The variation of time domain cutting force,frequency domain cutting force and tool temperature with process parameters are obtained.This study provides a new method for the prediction of cutting performance and the optimization of process parameters of indexable drills.展开更多
In this paper,two types of fractional nonlinear equations in Caputo sense,time-fractional Newell–Whitehead equation(FNWE)and time-fractional generalized Hirota–Satsuma coupled KdV system(HS-cKdVS),are investigated b...In this paper,two types of fractional nonlinear equations in Caputo sense,time-fractional Newell–Whitehead equation(FNWE)and time-fractional generalized Hirota–Satsuma coupled KdV system(HS-cKdVS),are investigated by means of the q-homotopy analysis method(q-HAM).The approximate solutions of the proposed equations are constructed in the form of a convergent series and are compared with the corresponding exact solutions.Due to the presence of the auxiliary parameter h in this method,just a few terms of the series solution are required in order to obtain better approximation.For the sake of visualization,the numerical results obtained in this paper are graphically displayed with the help of Maple.展开更多
The Laguerre polynomial method has been successfully used to investigate the dynamic responses of a half-space.However,it fails to obtain the correct stress at the interfaces in a layered half-space,especially when th...The Laguerre polynomial method has been successfully used to investigate the dynamic responses of a half-space.However,it fails to obtain the correct stress at the interfaces in a layered half-space,especially when there are significant differences in material properties.Therefore,a coupled Legendre-Laguerre polynomial method with analytical integration is proposed.The Rayleigh waves in a one-dimensional(1D)hexagonal quasicrystal(QC)layered half-space with an imperfect interface are investigated.The correctness is validated by comparison with available results.Its computation efficiency is analyzed.The dispersion curves of the phase velocity,displacement distributions,and stress distributions are illustrated.The effects of the phonon-phason coupling and imperfect interface coefficients on the wave characteristics are investigated.Some novel findings reveal that the proposed method is highly efficient for addressing the Rayleigh waves in a QC layered half-space.It can save over 99%of the computation time.This method can be expanded to investigate waves in various layered half-spaces,including earth-layered media and surface acoustic wave(SAW)devices.展开更多
In this paper,a simple direct space-time semi-analytical meshless scheme is proposed for the numerical approximation of the coupled Burgers'equations.During the whole solution procedure,two different schemes are c...In this paper,a simple direct space-time semi-analytical meshless scheme is proposed for the numerical approximation of the coupled Burgers'equations.During the whole solution procedure,two different schemes are considered in terms of radial and non-radial basis functions.The time-dependent variable in the first radial scheme is directly considered as the normal space variables to formulate an"isotropic"space-time radial basis function.The second non-radial scheme considered relationship between time-dependent and spacedependent variables.Under such circumstance,we can get a one-step space-time meshless scheme.The numerical findings demonstrate that the proposed meshless schemes are precise,user-friendly,and effective in solving the coupled Burgers'equations.展开更多
This paper presents a new approach to synthesize admittance function polynomials and coupling matrices for coupled resonator filters. The N + 2 transversal network method is applied to study a coupled resonator f...This paper presents a new approach to synthesize admittance function polynomials and coupling matrices for coupled resonator filters. The N + 2 transversal network method is applied to study a coupled resonator filter. This method allowed us to determine the polynomials of the reflection and transmission coefficients. A study is made for a 4 poles filter with 2 transmission zeros between the N + 2 transversal network method and the one found in the literature. A MATLAB code was designed for the numerical simulation of these coefficients for the 6, 8, and 10 pole filter with 4 transmission zeros.展开更多
An integrated fluid-thermal-structural analysis approach is presented. In this approach, the heat conduction in a solid is coupled with the heat convection in the viscous flow of the fluid resulting in the thermal str...An integrated fluid-thermal-structural analysis approach is presented. In this approach, the heat conduction in a solid is coupled with the heat convection in the viscous flow of the fluid resulting in the thermal stress in the solid. The fractional four-step finite element method and the streamline upwind Petrov-Galerkin （SUPG） method are used to analyze the viscous thermal flow in the fluid. Analyses of the heat transfer and the thermal stress in the solid axe performed by the Galerkin method. The second-order semi- implicit Crank-Nicolson scheme is used for the time integration. The resulting nonlinear equations are lineaxized to improve the computational efficiency. The integrated analysis method uses a three-node triangular element with equal-order interpolation functions for the fluid velocity components, the pressure, the temperature, and the solid displacements to simplify the overall finite element formulation. The main advantage of the present method is to consistently couple the heat transfer along the fluid-solid interface. Results of several tested problems show effectiveness of the present finite element method, which provides insight into the integrated fluid-thermal-structural interaction phenomena.展开更多
In this paper,the multi-body coupled dynamic characteristics of a semisubmersible platform and an HYSY 229 barge were investigated.First,coupled hydrodynamic analysis of the HYSY 229 barge and the semisubmersible plat...In this paper,the multi-body coupled dynamic characteristics of a semisubmersible platform and an HYSY 229 barge were investigated.First,coupled hydrodynamic analysis of the HYSY 229 barge and the semisubmersible platform was performed.Relevant hydrodynamic parameters were obtained using the retardation function method of three-dimensional frequency-domain potential flow theory.The results of the hydrodynamic analysis were highly consistent with the test findings,verifying the accuracy of the multifloating hydrodynamic coupling analysis,and key hydrodynamic parameters were solved for different water depths and the coupling effect.According to the obtained results,the hydrodynamic influence was the largest in shallow waters when the coupling effect was considered.Furthermore,the coupled motion equation combined with viscous damping,fender system,and mooring system was established,and the hydrodynamics,floating body motion,and dynamic response of the fender system were analyzed.Motion analysis revealed good agreement among the surge,sway,and yaw motions of the two floating bodies.However,when the wave period reached 10 s,the motion of the two floating bodies showed severe shock,and a relative motion was also observed.Therefore,excessive constraints should be added between the two floating bodies during construction to ensure construction safety.The numerical analysis and model test results of the semisubmersible platform and HYSY 229 barge at a water depth of 42 m and sea conditions of 0°,45°,and 90° were in good agreement,and the error was less than 5%.The maximum movement of the HYSY 229 barge reached 2.61 m in the sway direction,whereas that of the semisubmersible platform was 2.11 m.During construction,excessive constraints should be added between the two floating bodies to limit their relative movement and ensure construction safety.展开更多
The electrical performance of radomes on high-speed aircraft can be influenced by the thermal and mechanical loads produced during high-speed flight,which can affect the detection dis-tance and accuracy of the guidanc...The electrical performance of radomes on high-speed aircraft can be influenced by the thermal and mechanical loads produced during high-speed flight,which can affect the detection dis-tance and accuracy of the guidance system.This paper presents a new method that uses the Finite Difference Time Domain(FDTD)method to calculate the electrical performance of radomes under Thermo-Mechanical-Electrical(TME)coupling.This method can accurately characterize the effects of material dielectric temperature drift and structural deformation on the electrical performance of the radome under flight conditions,enabling high-precision full-wave calculations of the broadband electrical performance of the radome.The method initiates by utilizing a Finite Element Grid Model(FE-GM)of the radome to sequentially acquire the radome's response temperature field and structural deformation field through thermal and mechanical simulations.Subsequently,spatial mapping techniques are developed to accurately incorporate the dielectric temperature drift and structural deformation of the radome into its Yee grid Electromagnetic(EM)simulation model.A verification case was designed to test the proposed method,and the results confirmed its high computational accuracy.Additionally,the effectiveness and necessity of the method were further demonstrated by analyzing the electrical performance of a fused silica ceramic radome used on a high-speed aircraft.展开更多
基金financially supported by the National Key Research and Development Plan(2023YFC2811001)the National Natural Science Foundation of China(42206233)the Taishan Scholars Program(tsqn202312280,tsqn202306297)。
文摘Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs,as well as the stress interference patterns between fractures.This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluidsolid coupling discrete element method(DEM),and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance.The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30%and that fracture pressure increases with saturation.The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance.The distribution uniformity index(DUI)reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time,with fracturing efficiency depending on the spacing between injection points and the distance between wells.This work may provide reference for the commercial exploitation of natural gas hydrates.
基金a U.S. Federal Railroad Administration (FRA)BAA project,titled “Mitigation of Differential Movement at Railway Transitions for High-Speed Passenger Rail and Joint Passenger/Freight Corridors”the financial support provided by the China Scholarship Council (CSC),which funded Zhongyi Liu’s and Wenjing Li’s time and research efforts for this study
文摘Nonuniform track support and differential settlements are commonly observed in bridge approaches where the ballast layer can develop gaps at crosstie-ballast interfaces often referred to as a hanging crosstie condition.Hanging crossties usually yield unfavorable dynamic effects such as higher wheel loads,which negatively impact the serviceability and safety of railway operations.Hence,a better understanding of the mechanisms that cause hanging crossties and their effects on the ballast layer load-deformation characteristics is necessary.Since the ballast layer is a particulate medium,the discrete element method(DEM),which simulates ballast particle interactions individually,is ideal to explore the interparticle contact forces and ballast movements under dynamic wheel loading.Accurate representations of the dynamic loads from the train and track superstructure are needed for high-fidelity DEM modeling.This paper introduces an integrated modeling approach,which couples a single-crosstie DEM ballast model with a train–track–bridge(TTB)model using a proportional–integral–derivative control loop.The TTB–DEM model was validated with field measurements,and the coupled model calculates similar crosstie displacements as the TTB model.The TTB–DEM provided new insights into the ballast particle-scale behavior,which the TTB model alone cannot explore.The TTB–DEM coupling approach identified detrimental effects of hanging crossties on adjacent crossties,which were found to experience drastic vibrations and large ballast contact force concentrations.
基金financially supported by the National Natural Science Foundation of China(Nos.42272153 and 42472195)the Research Fund of PetroChina Tarim Oilfield Company(No.671023060003)the Research Fund of China National Petroleum Corporation Limited(No.2023ZZ16YJ04).
文摘Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression and permeability tests to investigate the mechanical and seepage properties of tight sandstone.A digital core of tight sandstone was built using Computed Tomography(CT)scanning,which was divided into matrix and pore phases by a pore equivalent diameter threshold.A fluid-solid coupling model was established to investigate the seepage characteristics at micro-scale.The results showed that increasing the confining pressure decreased porosity,permeability,and flow velocity,with the pore phase becoming the dominant seepage channel.Cracks and large pores closed first under increasing pressure,resulted in a steep drop in permeability.However,permeability slightly decreased under high confining pressure,which followed a first-order exponential function.Flow velocity increased with seepage pressure.And the damage mainly occurred in stress-concentration regions under low seepage pressure.Seepage behavior followed linear Darcy flow,the damage emerged at seepage entrances under high pressure,which decreased rock elastic modulus and significantly increased permeability.
基金Project supported by the National Natural Science Foundation of China(No.42202314)。
文摘A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution terms between the cold fluid and the hot rock are derived.Heat transfer obeys Fourier's law,and porosity is used to relate the thermodynamic parameters of the fracture and matrix domains.The net pressure difference between the fracture and the matrix is neglected,and thus the fluid flow is modeled by the unified fluid-governing equations.The evolution equations of porosity and Biot's coefficient during hydraulic fracturing are derived from their definitions.The effect of coal cleats is considered and modeled by Voronoi polygons,and this approach is shown to have high accuracy.The accuracy of the proposed model is verified by two sets of fracturing experiments in multilayer coal seams.Subsequently,the differences in fracture morphology,fluid pressure response,and fluid pressure distribution between direct fracturing of coal seams and indirect fracturing of shale interlayers are explored,and the effects of the cluster number and cluster spacing on fracture morphology for multi-cluster fracturing are also examined.The numerical results show that the proposed model is expected to be a powerful tool for the fracturing design and optimization of deep coalbed methane.
基金supported by the National Natural Science Foundation of China(Nos.U20A20111,41977229)the Sichuan Youth Science and Technology Innovation Research Team Project(No.2020JDTD0006).
文摘In the context of global warming and intensified human activities,glacier instability in plateau regions has increased,and glacier debris flows have become active,which poses a significant threat to the lives and property of people and socioeconomic development.The mass movement process of glacier debris flows is extremely complex,so this paper uses the 2018 Sedongpu glacier debris flow event on the Qinghai-Tibet Plateau as an example and applies a numerical simulation method to invert the whole process of mass movement.In view of the interaction between phases in the process of motion,we use the fluid-solid coupling method to describe the mass movement.The granular-flow model and drift-flux model are employed in FLOW3D software to study the mass movement process of glacier debris flows and explore their dynamic characteristics.The results indicate that the glacier debris flow lasted for 700 s,and the movement process was roughly divided into four stages,including initiation,scraping,surging and deposition;the depositional characteristics calculated by the fluid-solid coupling model are consistent with the actual survey results and have good reliability;strong erosion occurs during the mass movement,the clear volume amplification effect,and the first wave climbs 17.8 m across the slope.The fluid-solid coupling method can better simulate glacier debris flows in plateau regions,which is helpful for the study of the mechanism and dynamic characteristics of such disasters.
基金supported by the National Natural Science Foundation of China(Grant No.52374079)Chongqing Graduate Research Innovation Project(Grant No.CYB22032)Chongqing Talents and Outstanding Scientists Project(Grant No.cstc2024ycjhbgzxm0032).
文摘Deep underground excavation causes considerable unloading effects,leading to a pronounced bias pressure phenomenon.The deformation and seepage characteristics of rock masses under different gas and confining pressures were investigated via triaxial loading and unloading seepage tests.When the influential coefficient of effective confining pressure(β)is less than 0.065,the seepage force considerably weakens the strength of fractured rock masses.Conversely,whenβis greater than 0.065,the opposite is true.Moreover,the increase in the axial load leads to an increase in the precast fracture volumetric strain,which is the main reason for the increase in fracture permeability.This effect is particularly significant during the unloading stage.Based on the test results,a method for calculating the dynamic seepage evolution of rock masses,considering the effects of rock mass damage and fracture deformation,is introduced,and the effectiveness of the calculation is validated.The entire description of the seepage under loading and unloading was accomplished.The equivalent relationship between the lateral and normal stresses on fracture surfaces ranges from 0.001 to 0.1,showing an exponential variation between the lateral stress influence coefficient on normal deformation(χ)and seepage pressure.Before the failure of the rock mass,the seepage in the fractures was in a linear laminar flow state.However,after the failure,when the gas pressure reached 2 MPa,the flow state in the fractures transitioned to nonlinear laminar flow.The results are important for predicting hazardous gas leaks during deep underground engineering excavation.
基金financially supported by the Riset Pengembangan dan Penerapan(RPP),Diponegoro University 2023 research scheme with contract number 609-18/UN7.D2/PP/VIII/2023.
文摘Shallow water infrastructure needs to support increased activity on the shores of Semarang.This study chooses several pontoons because of their good stability,rolling motion,and more expansive space.A coupled simulation method consisting of hydrodynamic and structural calculations has been used to evaluate a catamaran pontoon’s motion and structural integrity.Four different space sizes are set for the pontoon system:5 m,5.5 m,6 m,and 6.5 m.The frequency domain shows that the pontoon space affects the RAO in wave periods ranging from 3 s to 5 s.At wave periods of 3 s,4 s,and 5 s,the pontoon space significantly affects the maximum motion and chain tension parameter values,which are evaluated via time domain simulation.The critical stress of the pontoon is shown at a wave period of 5 s for 5 m and 5.5 m of pontoon space,which shows that the stress can reach 248 MPa.
基金supported by the National Natural Science Foundation of China(Grant No.11925204).
文摘The Boussinesq equations,pivotal in the analysis of water wave dynamics,effectively model weakly nonlinear and long wave approximations.This study utilizes the complete discriminant system within a polynomial approach to derive exact traveling wave solutions for the coupled Boussinesq equation.The solutions are articulated through soliton,trigonometric,rational,and Jacobi elliptic functions.Notably,the introduction of Jacobi elliptic function solutions for this model marks a pioneering advancement.Contour plots of the solutions obtained by assigning values to various parameters are generated and subsequently analyzed.The methodology proposed in this study offers a systematic means to tackle nonlinear partial differential equations in mathematical physics,thereby enhancing comprehension of the physical attributes and dynamics of water waves.
基金financially supported by the National Natural Science Foundation of China(Grant No.42077231).
文摘This paper introduces a bond-based peridynamics(BB-PD)algorithm for crack identification,integrating the Delaunay triangulation method to accurately identify the structural characteristics of threedimensional(3D)cracks in rocks.A bond-based crack quantification standard is proposed to analyze the evolution of cracks of various sizes.A multi-attribute peridynamic model,developed using a multilayer algorithm,was employed to simulate the fracturing process of sandstone disks and semi-disks under varying temperatures,with the model calibrated and validated against experimental results.The simulation results show that temperature induces nonlinear degradation in the tensile strength and fracture toughness of sandstone,with 500℃ identified as the threshold temperature.Thermal cracks exhibit varying degrees of influence on Mode I cracks across different temperature ranges.Thermal damage significantly promotes the initiation and propagation of Mode I cracks in sandstone,thereby reducing its tensile strength and fracture toughness.Under applied loads,crack propagation in sandstone predominantly occurs during the failure stage,characterized by the rapid growth of longer cracks and a slow increase or reduction in shorter cracks.
基金supported by Alberta Health,Alberta Innovates,the Canada Research Chairs Program,the Canadian Institutes of Health Research,and the Natural Sciences and Engineering Research Council of Canada。
文摘Arsenic speciation in freshwater fish is crucial for providing meaningful consumption guidelines that allow the public to make informed decisions regarding its consumption.While marine fish have attractedmuch research interest due to their higher arsenic content,research on freshwater fish is limited due to the challenges in quantifying and identifying arsenic species present at trace levels.We describe here a sensitivemethod and its application to the quantification of arsenic species in freshwater fish.Arsenic species from fish tissues were extracted using a methanol/water mixture(1:1 vol.ratio)and ultrasound sonication.Anion-exchange high-performance liquid chromatography(HPLC)enabled separation of arsenobetaine(AsB),inorganic arsenite(iAs^(Ⅲ)),dimethylarsinic acid(DMA),monomethylarsonic acid(MMA),inorganic arsenate(iAs^(Ⅴ)),and three new arsenic species.Inductively coupled plasma mass spectrometry(ICPMS)provided highly sensitive and specific detection of arsenic.A limit of detection of 0.25μg/kg(wet weight fish tissue)was achieved for the five target arsenic species:AsB,iAs^(Ⅲ),DMA,MMA,and iAs^(Ⅴ).A series of experimentswere conducted to ensure the accuracy and validity of the analytical method.The method was successfully applied to the determination of arsenic species in lakewhitefish,northern pike,and walleye,with AsB,DMA,and iAs^(Ⅴ) being frequently detected.Three new arsenic species were detected,but their chromatographic retention times did not match with those of any available arsenic standards.Future research is necessary to elucidate the identity of these new arsenic species detected in freshwater fish.
文摘Spurious forces are a significant challenge for multi-scale methods,e.g.,the coupled atomistic/discrete dislocation(CADD)method.The assumption of isotropic matter in the continuum domain is a critical factor leading to such forces.This study aims to minimize spurious forces,ensuring that atomic dislocations experience more precise forces from the continuum domain.The authors have already implemented this idea using a simplified and unrealistic slipping system.To create a comprehensive and realistic model,this paper considers all possible slip systems in the face center cubic(FCC)lattice structure,and derives the required relationships for the displacement fields.An anisotropic version of the three-dimensional CADD(CADD3D)method is presented,which generates the anisotropic displacement fields for the partial dislocations in all the twelve slip systems of the FCC lattice structure.These displacement fields are tested for the most probable slip systems of aluminum,nickel,and copper with different anisotropic levels.Implementing these anisotropic displacement fields significantly reduces the spurious forces on the slip systems of FCC materials.This improvement is particularly pronounced at greater distances from the interface and in more anisotropic materials.Furthermore,the anisotropic CADD3D method enhances the spurious stress difference between the slip systems,particularly for materials with higher anisotropy.
基金the National Natural Science Foundation of China(No.51875062,No.52205336)the China Postdoctoral Science Foundation(No.2021M700567).
文摘The properties of the magnetic mold in magnetic mold casting directly determine the quality of the final cast parts.In this study,the magnetic mold properties in magnetic mold casting,were studied utilizing a coupled electromagnetic-structural method through numerical simulation.This study investigated key factors including equivalent stress,the distribution of tensile and compressive stresses,and the area ratio of tensile stress.It compared molds made entirely of magnetic materials with those made partially of magnetic materials.Simulation results indicate that as current increases from 4 A to 8 A,both the initial magnetic mold and the material-replaced magnetic mold initially show an increasing trend in equivalent stress,tensile-compressive stress,and the area ratio of tensile stress,peaking at 6 A before declining.After material replacement,the area ratio of tensile stress at 6 A decreases to 19.84%,representing a reduction of 29.72%.Magnetic molds comprising a combination of magnetic and non-magnetic materials exhibit sufficient strength and a reduced area ratio of tensile stress compared to those made entirely from magnetic materials.This study provides valuable insights for optimizing magnetic mold casting processes and offers practical guidance for advancing the application of magnetic molds.
基金supported by the Natural Science Foundation of Heilongjiang Province(No.TD2022E003)the National Natural Science Foundation of China(No.52175393)。
文摘42CrMo steel has the characteristics of high strength,high wear resistance,high impact resistance,and fatigue resistance.Therefore,drilling 42CrMo steel has always been a challenging task.The indexable drill bit has the advantages of high processing efficiency and low processing cost and has been widely used in the field of aerospace hole processing.To better understand the machining mechanism of the indexable drill bit,this paper uses the Coupled EulerianLagrangian method(CEL)to simulate the three-dimensional drilling model for the first time.The simulation results of the drilling force obtained by the CEL method and Lagrangian method are compared with the experimental results.It is verified that the CEL method is easy to converge and can avoid the problem of program interruption caused by mesh distortion,and the CEL simulation value is more consistent with the actual value.Secondly,the simulation results of cutting force and blade cutting edge node temperature under different process parameters are extracted.The variation of time domain cutting force,frequency domain cutting force and tool temperature with process parameters are obtained.This study provides a new method for the prediction of cutting performance and the optimization of process parameters of indexable drills.
基金supported by the National Natural Science Foundation of China(Grant No.12271433)。
文摘In this paper,two types of fractional nonlinear equations in Caputo sense,time-fractional Newell–Whitehead equation(FNWE)and time-fractional generalized Hirota–Satsuma coupled KdV system(HS-cKdVS),are investigated by means of the q-homotopy analysis method(q-HAM).The approximate solutions of the proposed equations are constructed in the form of a convergent series and are compared with the corresponding exact solutions.Due to the presence of the auxiliary parameter h in this method,just a few terms of the series solution are required in order to obtain better approximation.For the sake of visualization,the numerical results obtained in this paper are graphically displayed with the help of Maple.
基金Project supported by the National Natural Science Foundation of China(No.12102131)the Natural Science Foundation of Henan Province of China(No.242300420248)the International Science and Technology Cooperation Project of Henan Province of China(No.242102521010)。
文摘The Laguerre polynomial method has been successfully used to investigate the dynamic responses of a half-space.However,it fails to obtain the correct stress at the interfaces in a layered half-space,especially when there are significant differences in material properties.Therefore,a coupled Legendre-Laguerre polynomial method with analytical integration is proposed.The Rayleigh waves in a one-dimensional(1D)hexagonal quasicrystal(QC)layered half-space with an imperfect interface are investigated.The correctness is validated by comparison with available results.Its computation efficiency is analyzed.The dispersion curves of the phase velocity,displacement distributions,and stress distributions are illustrated.The effects of the phonon-phason coupling and imperfect interface coefficients on the wave characteristics are investigated.Some novel findings reveal that the proposed method is highly efficient for addressing the Rayleigh waves in a QC layered half-space.It can save over 99%of the computation time.This method can be expanded to investigate waves in various layered half-spaces,including earth-layered media and surface acoustic wave(SAW)devices.
基金the Science and Technology Research Project of Henan Province (242102231052)the Key Scientific Research Plan of Colleges and Universities in Henan Province (23B140006)the Natural Science Foundation of Jiangxi Province (20224BAB201018)。
文摘In this paper,a simple direct space-time semi-analytical meshless scheme is proposed for the numerical approximation of the coupled Burgers'equations.During the whole solution procedure,two different schemes are considered in terms of radial and non-radial basis functions.The time-dependent variable in the first radial scheme is directly considered as the normal space variables to formulate an"isotropic"space-time radial basis function.The second non-radial scheme considered relationship between time-dependent and spacedependent variables.Under such circumstance,we can get a one-step space-time meshless scheme.The numerical findings demonstrate that the proposed meshless schemes are precise,user-friendly,and effective in solving the coupled Burgers'equations.
文摘This paper presents a new approach to synthesize admittance function polynomials and coupling matrices for coupled resonator filters. The N + 2 transversal network method is applied to study a coupled resonator filter. This method allowed us to determine the polynomials of the reflection and transmission coefficients. A study is made for a 4 poles filter with 2 transmission zeros between the N + 2 transversal network method and the one found in the literature. A MATLAB code was designed for the numerical simulation of these coefficients for the 6, 8, and 10 pole filter with 4 transmission zeros.
基金the National Metal and Materials Technology Centerthe Thailand Research Fund+1 种基金the Office of Higher Education Commissionthe Chulalongkorn University for supporting the present research
文摘An integrated fluid-thermal-structural analysis approach is presented. In this approach, the heat conduction in a solid is coupled with the heat convection in the viscous flow of the fluid resulting in the thermal stress in the solid. The fractional four-step finite element method and the streamline upwind Petrov-Galerkin （SUPG） method are used to analyze the viscous thermal flow in the fluid. Analyses of the heat transfer and the thermal stress in the solid axe performed by the Galerkin method. The second-order semi- implicit Crank-Nicolson scheme is used for the time integration. The resulting nonlinear equations are lineaxized to improve the computational efficiency. The integrated analysis method uses a three-node triangular element with equal-order interpolation functions for the fluid velocity components, the pressure, the temperature, and the solid displacements to simplify the overall finite element formulation. The main advantage of the present method is to consistently couple the heat transfer along the fluid-solid interface. Results of several tested problems show effectiveness of the present finite element method, which provides insight into the integrated fluid-thermal-structural interaction phenomena.
基金the National Natural Science Foundation of China(No.U20A20328).
文摘In this paper,the multi-body coupled dynamic characteristics of a semisubmersible platform and an HYSY 229 barge were investigated.First,coupled hydrodynamic analysis of the HYSY 229 barge and the semisubmersible platform was performed.Relevant hydrodynamic parameters were obtained using the retardation function method of three-dimensional frequency-domain potential flow theory.The results of the hydrodynamic analysis were highly consistent with the test findings,verifying the accuracy of the multifloating hydrodynamic coupling analysis,and key hydrodynamic parameters were solved for different water depths and the coupling effect.According to the obtained results,the hydrodynamic influence was the largest in shallow waters when the coupling effect was considered.Furthermore,the coupled motion equation combined with viscous damping,fender system,and mooring system was established,and the hydrodynamics,floating body motion,and dynamic response of the fender system were analyzed.Motion analysis revealed good agreement among the surge,sway,and yaw motions of the two floating bodies.However,when the wave period reached 10 s,the motion of the two floating bodies showed severe shock,and a relative motion was also observed.Therefore,excessive constraints should be added between the two floating bodies during construction to ensure construction safety.The numerical analysis and model test results of the semisubmersible platform and HYSY 229 barge at a water depth of 42 m and sea conditions of 0°,45°,and 90° were in good agreement,and the error was less than 5%.The maximum movement of the HYSY 229 barge reached 2.61 m in the sway direction,whereas that of the semisubmersible platform was 2.11 m.During construction,excessive constraints should be added between the two floating bodies to limit their relative movement and ensure construction safety.
文摘The electrical performance of radomes on high-speed aircraft can be influenced by the thermal and mechanical loads produced during high-speed flight,which can affect the detection dis-tance and accuracy of the guidance system.This paper presents a new method that uses the Finite Difference Time Domain(FDTD)method to calculate the electrical performance of radomes under Thermo-Mechanical-Electrical(TME)coupling.This method can accurately characterize the effects of material dielectric temperature drift and structural deformation on the electrical performance of the radome under flight conditions,enabling high-precision full-wave calculations of the broadband electrical performance of the radome.The method initiates by utilizing a Finite Element Grid Model(FE-GM)of the radome to sequentially acquire the radome's response temperature field and structural deformation field through thermal and mechanical simulations.Subsequently,spatial mapping techniques are developed to accurately incorporate the dielectric temperature drift and structural deformation of the radome into its Yee grid Electromagnetic(EM)simulation model.A verification case was designed to test the proposed method,and the results confirmed its high computational accuracy.Additionally,the effectiveness and necessity of the method were further demonstrated by analyzing the electrical performance of a fused silica ceramic radome used on a high-speed aircraft.
