Rock is geometrically and mechanically multiscale in nature,and the traditional phenomenological laws at the macroscale cannot render a quantitative relationship between microscopic damage of rocks and overall rock st...Rock is geometrically and mechanically multiscale in nature,and the traditional phenomenological laws at the macroscale cannot render a quantitative relationship between microscopic damage of rocks and overall rock structural degradation.This may lead to problems in the evaluation of rock structure stability and safe life.Multiscale numerical modeling is regarded as an effective way to gain insight into factors affecting rock properties from a cross-scale view.This study compiles the history of theoretical developments and numerical techniques related to rock multiscale issues according to different modeling architectures,that is,the homogenization theory,the hierarchical approach,and the concurrent approach.For these approaches,their benefits,drawbacks,and application scope are underlined.Despite the considerable attempts that have been made,some key issues still result in multiple challenges.Therefore,this study points out the perspectives of rock multiscale issues so as to provide a research direction for the future.The review results show that,in addition to numerical techniques,for example,high-performance computing,more attention should be paid to the development of an advanced constitutive model with consideration of fine geometrical descriptions of rock to facilitate solutions to multiscale problems in rock mechanics and rock engineering.展开更多
Software systems are vulnerable to security breaches as they expand in complexity and functionality.The confidentiality,integrity,and availability of data are gravely threatened by flaws in a system’s design,implemen...Software systems are vulnerable to security breaches as they expand in complexity and functionality.The confidentiality,integrity,and availability of data are gravely threatened by flaws in a system’s design,implementation,or configuration.To guarantee the durability&robustness of the software,vulnerability identification and fixation have become crucial areas of focus for developers,cybersecurity experts and industries.This paper presents a thorough multi-phase mathematical model for efficient patch management and vulnerability detection.To uniquely model these processes,the model incorporated the notion of the learning phenomenon in describing vulnerability fixation using a logistic learning function.Furthermore,the authors have used numerical methods to approximate the solution of the proposed framework where an analytical solution is difficult to attain.The suggested systematic architecture has been demonstrated through statistical analysis using patch datasets,which offers a solid basis for the research conclusions.According to computational research,learning dynamics improves security response and results in more effective vulnerability management.The suggested model offers a systematic approach to proactive vulnerability mitigation and has important uses in risk assessment,software maintenance,and cybersecurity.This study helps create more robust software systems by increasing patch management effectiveness,which benefits developers,cybersecurity experts,and sectors looking to reduce security threats in a growing digital world.展开更多
With the increasing development of deepburied engineering projects,rockburst disasters have become a frequent concern.Studies have indicated that tunnel diameter is a critical factor influencing the occurrence of rock...With the increasing development of deepburied engineering projects,rockburst disasters have become a frequent concern.Studies have indicated that tunnel diameter is a critical factor influencing the occurrence of rockbursts.To investigate the influence of tunnel diameter on the deformation and failure characteristics of surrounding rock,large-sized rocklike gypsum specimens were tested using a selfdeveloped true triaxial rockburst loading system containing circular tunnels with three different diameters(D=0.07 m,0.11 m,and 0.15 m).Acoustic emission monitoring,together with a miniature intelligent camera,was employed to analyze the entire process,focusing on macroscopic failure patterns,fragment characteristics,and underlying failure mechanisms.In addition,theoretical analyses were carried out and combined with numerical simulations to investigate the differences in energy evolution associated with rockburst physical models.The results indicate that:(1)The rockburst process with different tunnel diameters consistently evolved through three distinct stages—initial particle ejection,crack propagation accompanied by flake spalling,and,finally,fragment ejection leading to the formation of a‘V'-shaped notch.(2)Increasing tunnel diameter reduces rockburst failure load while increasing surrounding rock damage extent,total mass and average size of ejected fragments.Additionally,shear failure proportion decreases with tensile failure becoming increasingly dominant.(3)Larger tunnel diameters reduce the attenuation rate of elastic strain energy,thereby expanding the zone of elastic strain energy accumulation and disturbance and creating conditions for larger volume rockburst.(4)Larger tunnel diameters result in a smaller principal stress ratio at equivalent distances in the surrounding rock,indicating a higher likelihood of tensile failure.(5)Numerical analyses further reveal that larger tunnel diameters reduce the maximum elastic strain energy density around the tunnel,lowering the energy released per unit volume of rockburst fragments and their ejection velocities.However,both the total failure volume and overall energy release from rockburst increase.Model experiments with different tunnel diameters are of great significance for optimizing engineering design and parameter selection,as well as guiding tunnel construction under complex geological conditions.展开更多
The nozzle is a critical component responsible for generating most of the net thrust in a scramjet engine.The quality of its design directly affects the performance of the entire propulsion system.However,most turbule...The nozzle is a critical component responsible for generating most of the net thrust in a scramjet engine.The quality of its design directly affects the performance of the entire propulsion system.However,most turbulence models struggle to make accurate predictions for subsonic and supersonic flows in nozzles.In this study,we explored a novel model,the algebraic stress model k-kL-ARSM+J,to enhance the accuracy of turbulence numerical simulations.This new model was used to conduct numerical simulations of the design and off-design performance of a 3D supersonic asymmetric truncated nozzle designed in our laboratory,with the aim of providing a realistic pattern of changes.The research indicates that,compared to linear eddy viscosity turbulence models such as k-kL and shear stress transport(SST),the k-kL-ARSM+J algebraic stress model shows better accuracy in predicting the performance of supersonic nozzles.Its predictions were identical to the experimental values,enabling precise calculations of the nozzle.The performance trends of the nozzle are as follows:as the inlet Mach number increases,both thrust and pitching moment increase,but the rate of increase slows down.Lift peaks near the design Mach number and then rapidly decreases.With increasing inlet pressure,the nozzle thrust,lift,and pitching moment all show linear growth.As the flight altitude rises,the internal flow field within the nozzle remains relatively consistent due to the same supersonic nozzle inlet flow conditions.However,external to the nozzle,the change in external flow pressure results in the nozzle exit transitioning from over-expanded to under-expanded,leading to a shear layer behind the nozzle that initially converges towards the nozzle center and then diverges.展开更多
Systematic bias is a type of model error that can affect the accuracy of data assimilation and forecasting that must be addressed.An online bias correction scheme called the sequential bias correction scheme(SBCS),was...Systematic bias is a type of model error that can affect the accuracy of data assimilation and forecasting that must be addressed.An online bias correction scheme called the sequential bias correction scheme(SBCS),was developed using the6 h average bias to correct the systematic bias during model integration.The primary purpose of this study is to investigate the impact of the SBCS in the high-resolution China Meteorological Administration Meso-scale(CMA-MESO)numerical weather prediction(NWP)model to reduce the systematic bias and to improve the data assimilation and forecast results through this method.The SBCS is improved upon and applied to the CMA-MESO 3-km model in this study.Four-week sequential data assimilation and forecast experiments,driven by rapid update and cycling(RUC),were conducted for the period from 2–29 May 2022.In terms of the characteristics of systematic bias,both the background and analysis show diurnal bias,and these large biases are affected by complex underlying surfaces(e.g.,oceans,coasts,and mountains).After the application of the SBCS,the results of the data assimilation show that the SBCS can reduce the systematic bias of the background and yield a neutral to slightly positive result for the analysis fields.In addition,the SBCS can reduce forecast errors and improve forecast results,especially for surface variables.The above results indicate that this scheme has good prospects for high-resolution regional NWP models.展开更多
Oilfields worldwide are increasingly grappling with challenges such as early water breakthrough and high water production,yet direct,targeted solutions remain elusive.In recent years,chemical flooding techniques desig...Oilfields worldwide are increasingly grappling with challenges such as early water breakthrough and high water production,yet direct,targeted solutions remain elusive.In recent years,chemical flooding techniques designed for tertiary oil recovery have garnered significant attention,with microgel flooding emerging as a particularly prominent area of research.Despite its promise,the complex mechanisms underlying microgel flooding have been rarely investigated numerically.This study aims to address these gaps by characterizing the distribution of microgel concentration and viscosity within different pore structures.To enhance the accuracy of these characterizations,the viscosity of microgels is adjusted to account for the shear effects induced by flow rate and the swelling effects driven by salinity variations.The absolute permeability of the rock and the relative permeability of both oil and microgel are also analyzed to elucidate the mechanisms of microgel flooding.Additionally,a connectivity model is employed to achieve a quantitative representation of fluid flow capacity.The proposed model is validated through conceptual examples and applied to real oilfield blocks,demonstrating its accuracy and practical applicability.展开更多
Polymer flooding is an important means of improving oil recovery and is widely used in Daqing,Xinjiang,and Shengli oilfields,China.Different from conventional injection media such as water and gas,viscoelastic polymer...Polymer flooding is an important means of improving oil recovery and is widely used in Daqing,Xinjiang,and Shengli oilfields,China.Different from conventional injection media such as water and gas,viscoelastic polymer solutions exhibit non-Newtonian and nonlinear flow behavior including shear thinning and shear thickening,polymer convection,diffusion,adsorption,retention,inaccessible pore volume,and reduced effective permeability.However,available well test model of polymer flooding wells generally simplifies these characteristics on pressure transient response,which may lead to inaccurate results.This work proposes a novel two-phase numerical well test model to better describe the polymer viscoelasticity and nonlinear flow behavior.Different influence factors that related to near-well blockage during polymer flooding process,including the degree of blockage(inner zone permeability),the extent of blockage(composite radius),and polymer flooding front radius are explored to investigate these impacts on bottom hole pressure responses.Results show that polymer viscoelasticity has a significant impact on the transitional flow segment of type curves,and the effects of near-well formation blockage and polymer concentration distribution on well test curves are very similar.Thus,to accurately interpret the degree of near-well blockage in injection wells,it is essential to first eliminate the influence of polymer viscoelasticity.Finally,a field case is comprehensively analyzed and discussed to illustrate the applicability of the proposed model.展开更多
The multi-scale modeling combined with the cohesive zone model(CZM)and the molecular dynamics(MD)method were preformed to simulate the crack propagation in NiTi shape memory alloys(SMAs).The metallographic microscope ...The multi-scale modeling combined with the cohesive zone model(CZM)and the molecular dynamics(MD)method were preformed to simulate the crack propagation in NiTi shape memory alloys(SMAs).The metallographic microscope and image processing technology were employed to achieve a quantitative grain size distribution of NiTi alloys so as to provide experimental data for molecular dynamics modeling at the atomic scale.Considering the size effect of molecular dynamics model on material properties,a reasonable modeling size was provided by taking into account three characteristic dimensions from the perspective of macro,meso,and micro scales according to the Buckinghamπtheorem.Then,the corresponding MD simulation on deformation and fracture behavior was investigated to derive a parameterized traction-separation(T-S)law,and then it was embedded into cohesive elements of finite element software.Thus,the crack propagation behavior in NiTi alloys was reproduced by the finite element method(FEM).The experimental results show that the predicted initiation fracture toughness is in good agreement with experimental data.In addition,it is found that the dynamics initiation fracture toughness increases with decreasing grain size and increasing loading velocity.展开更多
A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of ...A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of shielding gases with varying He-Ar ratios,and the coupling between arc plasma and laser-induced metal plume.The accuracy of the model is validated using a high-speed camera.The effects of varying He contents in the shielding gas on both the temperature and flow velocity of hybrid plasma,as well as the distribu-tion of laser-induced metal vapor mass,were investigated separately.The maximum temperature and size of arc plasma decrease as the He volume ratio increases,the arc distribution becomes more concentrated,and its flow velocity initially decreases and then sharply increases.At high helium content,both the flow velocity of hybrid plasma and metal vapor are high,the metal vapor is con-centrated on the right side of keyhole,and its flow appears chaotic.The flow state of arc plasma is most stable when the shielding gas consists of 50%He+50%Ar.展开更多
A process-based 3D numerical model for surfzone hydrodynamics and beach evolution was established. Comparisons between the experimental data and model results proved that the model could effectively describe the hydro...A process-based 3D numerical model for surfzone hydrodynamics and beach evolution was established. Comparisons between the experimental data and model results proved that the model could effectively describe the hydrodynamics, sediment transport feature and sandbar migration process in the surfzone with satisfactory precision. A series of numerical simulations on the wave breaking and shoaling up to a barred beach were carried out based on the model system. Analyzed from the model results, the wave-induced current system in the surfzone consists of two major processes, which are the phase-averaged undertow caused by wave breaking and the net drift caused by both of the nonlinear wave motion and surface roller effect. When storm waves come to the barred beach, the strong offshore undertow along the beach suppresses the onshore net drift, making the initial sandbar migrate to the seaside. Under the condition of calm wave environment, both the undertow and net drift flow to the shoreline at the offshore side of the sandbar, and then push the initial sandbar to the shoreline. The consideration of surface roller has significant impact on the modeling results of the sandbar migration. As the roller transfer rate increases, the sandbar moves onshore especially under the storm wave condition.展开更多
In order to investigate the fatigue behavior of asphalt concrete, a new numerical approach based on a bi-linear cohesive zone model （CZM） is developed. Integrated with the CZM, a fatigue damage evolution model is es...In order to investigate the fatigue behavior of asphalt concrete, a new numerical approach based on a bi-linear cohesive zone model （CZM） is developed. Integrated with the CZM, a fatigue damage evolution model is established to indicate the gradual degradation of cohesive properties of asphalt concrete under cyclic loading. Then the model is implemented in the finite element software ABAQUS through a user-defined subroutine. Based on the proposed model, an indirect tensile fatigue test is finally simulated. The fatigue lives obtained through numerical analysis show good agreement with laboratory results. Fatigue damage accumulates in a nonlinear manner during the cyclic loading process and damage initiation phase is the major part of fatigue failure. As the stress ratio increases, the time of the steady damage growth stage decreases significantly. It is found that the proposed fatigue damage evolution model can serve as an accurate and efficient tool for the prediction of fatigue damage of asphalt concrete.展开更多
Biot-flow and squirt-flow are the two most important fluid flow mechanisms in porous media containing fluids. Based on the BISQ （Biot-Squirt） model where the two mechanisms are treated simultaneously, the elastic wa...Biot-flow and squirt-flow are the two most important fluid flow mechanisms in porous media containing fluids. Based on the BISQ （Biot-Squirt） model where the two mechanisms are treated simultaneously, the elastic wave-field simulation in the porous medium is limited to two-dimensions and two-components （2D2C） or two-dimensions and three-components （2D3C）. There is no previous report on wave simulation in three- dimensions and three-components. Only through three dimensional numerical simulations can we have an overall understanding of wave field coupling relations and the spatial distribution characteristics between the solid and fluid phases in the dual-phase anisotropic medium. In this paper, based on the BISQ equation, we present elastic wave propagation in a three dimensional dual-phase anisotropic medium simulated by the staggered-grid high-order finite-difference method. We analyze the resulting wave fields and show that the results are an improvement.展开更多
To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional （2D） time- domain transient electromagnetic secondary field of t...To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional （2D） time- domain transient electromagnetic secondary field of the line source based on the DuFort- Frankel finite-difference method. In the proposed method, we included the treatment of the earth-air boundary conductivity, calculated the normalized partial derivative of the induced electromotive force （Emf）, and determined the forward time step. By extending upward the earth-air interface to the air grid nodes and the zero-value boundary conditions, not only we have a method that is more efficient but also simpler than the total field solution. We computed and analyzed the homogeneous half-space model and the fiat layered model with high precision--the maximum relative error is less than 0.01% between our method and the analytical method--and the solution speed is roughly three times faster than the total-field solution. Lastly, we used the model of a thin body embedded in a homogeneous half-space at different delay times to depict the downward and upward spreading characteristics of the induced eddy current, and the physical interaction processes between the electromagnetic field and the underground low-resistivity body.展开更多
This study focuses on the factors that may affect the feasibility of performing elliptical anisotropy analysis on azimuthal PP and PS-wave data in HTI media, with the aim of using the modeling results as guidance in r...This study focuses on the factors that may affect the feasibility of performing elliptical anisotropy analysis on azimuthal PP and PS-wave data in HTI media, with the aim of using the modeling results as guidance in real seismic data application. Our results reveal that there is an offset limitation for both PP- and PS-waves in elliptical anisotropy fitting, and that PS-waves show a wider applicable offset range and larger observable azimuthal anisotropy than PP-waves. The major axis of the elliptical fit to the amplitudes of the R-component is perpendicular to the fracture strike, which is opposite to that in PP-wave analysis. The azimuthal interval travel time of PS-waves shows a nearly elliptical distribution and the major axis of the fit ellipse is perpendicular to the fracture strike, which is same as that in PP-wave analysis. For data within the applicable offset range, the anisotropic magnitude obtained from amplitude and travel time attributes of PP- and PS-waves exhibits a dependence on fracture density, and the major to minor axis ratio of the fit ellipse may be used to infer the relative distribution of fracture densities.展开更多
In order to reasonably simulate tidal currents around small structures such as piles in a large-scale model domain, a 2-D hydrodynamic integrated model for Bohai Sea is established with the finite element method. The ...In order to reasonably simulate tidal currents around small structures such as piles in a large-scale model domain, a 2-D hydrodynamic integrated model for Bohai Sea is established with the finite element method. The grid can be discretionarily refined as a non-structure triangle or quadrilateral so that piers can be treated as one or several impermeable elements with an area of 20 to 30 km^2 in a model domain over 85 700 km^2. The computational results of tidal levels and horizontal velocities are in good agreement with the field data. Based on the computed results by the model, the layout of an open 105 DWT liquefied natural gas （LNG）terminal in Caofeidian, Bohal Sea is effectively and reasonably optimized. It can be concluded that the model is suitable and reasonable for direct simulation of tidal currents around small structures in projects.展开更多
To improve the accuracy of the conventional finite-difference method, finitedifference numerical modeling methods of any even-order accuracy are recommended. We introduce any even-order accuracy difference schemes of ...To improve the accuracy of the conventional finite-difference method, finitedifference numerical modeling methods of any even-order accuracy are recommended. We introduce any even-order accuracy difference schemes of any-order derivatives derived from Taylor series expansion. Then, a finite-difference numerical modeling method with any evenorder accuracy is utilized to simulate seismic wave propagation in two-phase anisotropic media. Results indicate that modeling accuracy improves with the increase of difference accuracy order number. It is essential to find the optimal order number, grid size, and time step to balance modeling precision and computational complexity. Four kinds of waves, static mode in the source point, SV wave cusps, reflection and transmission waves are observed in two-phase anisotropic media through modeling.展开更多
Haihua Islands is a large artificial island in Danzhou, Hainan. The construction of Haihua Islands changes the hYdrodynamic environment of Yangpu waters, and further affects its morphological change. Delft3D is used t...Haihua Islands is a large artificial island in Danzhou, Hainan. The construction of Haihua Islands changes the hYdrodynamic environment of Yangpu waters, and further affects its morphological change. Delft3D is used to set up a two dimensional nested hydrodynamic and sediment model for Yangpu waters in this paper, and this paper focuses on simulating the velocity and morphological change due to the construction of Haihua Islands after the verification of the model. The seabed deposition is small because of low suspended sediment concentration and less sand source near Yangpu waters. The bed level erodes in the south area of Xiaochan Reef and the Yangpu channel due to the velocity increase in the area.展开更多
A mathematical model of resin flow and temperature variation in the filling stage of the resin transfer molding (RTM) is developed based on the control volume/finite element method (CV/FEM). The effects of the heat tr...A mathematical model of resin flow and temperature variation in the filling stage of the resin transfer molding (RTM) is developed based on the control volume/finite element method (CV/FEM). The effects of the heat transfer and chemical reaction of the resin on the flow and temperature are considered. The numerical algorithm of the resin flow and temperature variation in the process of RTM are studied. Its accuracy and convergence are analyzed. The comparison of temperature variations between experimental results and model predictions is carried out for two RTM cases. Result shows that the model is efficient for evaluating the flow and temperature variation in the filling stage of RTM and there is a good coincidence between theory and experiment.展开更多
Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the invest...Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the investigated powder Distaloy AE were determined as functions of relative density through typical mechanical property tests of powder. The model was implemented as a user subroutine USDFLD. Single sided compaction of a d20 ram^5 mm disk green compact of Distaloy AE was simulated, and the residual stress of the disk after ejection was predicted with FEA. The FEA results of the compaction process and the residual stress of the disk show good agreement with compaction experiments and X-ray diffraction measurements, which validates the model and its parameters. The results indicate that the compressive residual stresses exist mainly in a thin layer on the side surface, but the residual stresses are very small on the top and bottom surfaces.展开更多
This review summarizes the scientific and technical progress in atmospheric modeling in China since 2011,including the dynamical core,model physics,data assimilation,ensemble forecasting,and model evaluation strategie...This review summarizes the scientific and technical progress in atmospheric modeling in China since 2011,including the dynamical core,model physics,data assimilation,ensemble forecasting,and model evaluation strategies.In terms of the dynamical core,important efforts have been made in the improvement of the existing model formulations and in exploring new modeling approaches that can better adapt to massively parallel computers and global multiscale modeling.With regard to model physics,various achievements in physical representations have been made,especially a trend toward scale-aware parameterization for accommodating the increase of model resolution.In the field of data assimilation,a 4D-Var system has been developed and is operationally used by the National Meteorological Center of China,and its performance is promising.Furthermore,ensemble forecasting has played a more important role in operational forecast systems and progressed in many fundamental techniques.Model evaluation strategies,including key performance metrics and standardized experimental protocols,have been proposed and widely applied to better understand the strengths and weaknesses of the systems,offering key routes for model improvement.The paper concludes with a concise summary of the status quo and a brief outlook in terms of future development.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:52192691,52192690。
文摘Rock is geometrically and mechanically multiscale in nature,and the traditional phenomenological laws at the macroscale cannot render a quantitative relationship between microscopic damage of rocks and overall rock structural degradation.This may lead to problems in the evaluation of rock structure stability and safe life.Multiscale numerical modeling is regarded as an effective way to gain insight into factors affecting rock properties from a cross-scale view.This study compiles the history of theoretical developments and numerical techniques related to rock multiscale issues according to different modeling architectures,that is,the homogenization theory,the hierarchical approach,and the concurrent approach.For these approaches,their benefits,drawbacks,and application scope are underlined.Despite the considerable attempts that have been made,some key issues still result in multiple challenges.Therefore,this study points out the perspectives of rock multiscale issues so as to provide a research direction for the future.The review results show that,in addition to numerical techniques,for example,high-performance computing,more attention should be paid to the development of an advanced constitutive model with consideration of fine geometrical descriptions of rock to facilitate solutions to multiscale problems in rock mechanics and rock engineering.
基金supported by grants received by the first author and third author from the Institute of Eminence,Delhi University,Delhi,India,as part of the Faculty Research Program via Ref.No./IoE/2024-25/12/FRP.
文摘Software systems are vulnerable to security breaches as they expand in complexity and functionality.The confidentiality,integrity,and availability of data are gravely threatened by flaws in a system’s design,implementation,or configuration.To guarantee the durability&robustness of the software,vulnerability identification and fixation have become crucial areas of focus for developers,cybersecurity experts and industries.This paper presents a thorough multi-phase mathematical model for efficient patch management and vulnerability detection.To uniquely model these processes,the model incorporated the notion of the learning phenomenon in describing vulnerability fixation using a logistic learning function.Furthermore,the authors have used numerical methods to approximate the solution of the proposed framework where an analytical solution is difficult to attain.The suggested systematic architecture has been demonstrated through statistical analysis using patch datasets,which offers a solid basis for the research conclusions.According to computational research,learning dynamics improves security response and results in more effective vulnerability management.The suggested model offers a systematic approach to proactive vulnerability mitigation and has important uses in risk assessment,software maintenance,and cybersecurity.This study helps create more robust software systems by increasing patch management effectiveness,which benefits developers,cybersecurity experts,and sectors looking to reduce security threats in a growing digital world.
基金funded by the National Natural Science Foundation of China(Nos.42077228,52174085)。
文摘With the increasing development of deepburied engineering projects,rockburst disasters have become a frequent concern.Studies have indicated that tunnel diameter is a critical factor influencing the occurrence of rockbursts.To investigate the influence of tunnel diameter on the deformation and failure characteristics of surrounding rock,large-sized rocklike gypsum specimens were tested using a selfdeveloped true triaxial rockburst loading system containing circular tunnels with three different diameters(D=0.07 m,0.11 m,and 0.15 m).Acoustic emission monitoring,together with a miniature intelligent camera,was employed to analyze the entire process,focusing on macroscopic failure patterns,fragment characteristics,and underlying failure mechanisms.In addition,theoretical analyses were carried out and combined with numerical simulations to investigate the differences in energy evolution associated with rockburst physical models.The results indicate that:(1)The rockburst process with different tunnel diameters consistently evolved through three distinct stages—initial particle ejection,crack propagation accompanied by flake spalling,and,finally,fragment ejection leading to the formation of a‘V'-shaped notch.(2)Increasing tunnel diameter reduces rockburst failure load while increasing surrounding rock damage extent,total mass and average size of ejected fragments.Additionally,shear failure proportion decreases with tensile failure becoming increasingly dominant.(3)Larger tunnel diameters reduce the attenuation rate of elastic strain energy,thereby expanding the zone of elastic strain energy accumulation and disturbance and creating conditions for larger volume rockburst.(4)Larger tunnel diameters result in a smaller principal stress ratio at equivalent distances in the surrounding rock,indicating a higher likelihood of tensile failure.(5)Numerical analyses further reveal that larger tunnel diameters reduce the maximum elastic strain energy density around the tunnel,lowering the energy released per unit volume of rockburst fragments and their ejection velocities.However,both the total failure volume and overall energy release from rockburst increase.Model experiments with different tunnel diameters are of great significance for optimizing engineering design and parameter selection,as well as guiding tunnel construction under complex geological conditions.
基金supported by the Zhejiang Provincial Key Research and Development Program of China(No.2020C01020).
文摘The nozzle is a critical component responsible for generating most of the net thrust in a scramjet engine.The quality of its design directly affects the performance of the entire propulsion system.However,most turbulence models struggle to make accurate predictions for subsonic and supersonic flows in nozzles.In this study,we explored a novel model,the algebraic stress model k-kL-ARSM+J,to enhance the accuracy of turbulence numerical simulations.This new model was used to conduct numerical simulations of the design and off-design performance of a 3D supersonic asymmetric truncated nozzle designed in our laboratory,with the aim of providing a realistic pattern of changes.The research indicates that,compared to linear eddy viscosity turbulence models such as k-kL and shear stress transport(SST),the k-kL-ARSM+J algebraic stress model shows better accuracy in predicting the performance of supersonic nozzles.Its predictions were identical to the experimental values,enabling precise calculations of the nozzle.The performance trends of the nozzle are as follows:as the inlet Mach number increases,both thrust and pitching moment increase,but the rate of increase slows down.Lift peaks near the design Mach number and then rapidly decreases.With increasing inlet pressure,the nozzle thrust,lift,and pitching moment all show linear growth.As the flight altitude rises,the internal flow field within the nozzle remains relatively consistent due to the same supersonic nozzle inlet flow conditions.However,external to the nozzle,the change in external flow pressure results in the nozzle exit transitioning from over-expanded to under-expanded,leading to a shear layer behind the nozzle that initially converges towards the nozzle center and then diverges.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2242213,U2142213,42305167,42175105)。
文摘Systematic bias is a type of model error that can affect the accuracy of data assimilation and forecasting that must be addressed.An online bias correction scheme called the sequential bias correction scheme(SBCS),was developed using the6 h average bias to correct the systematic bias during model integration.The primary purpose of this study is to investigate the impact of the SBCS in the high-resolution China Meteorological Administration Meso-scale(CMA-MESO)numerical weather prediction(NWP)model to reduce the systematic bias and to improve the data assimilation and forecast results through this method.The SBCS is improved upon and applied to the CMA-MESO 3-km model in this study.Four-week sequential data assimilation and forecast experiments,driven by rapid update and cycling(RUC),were conducted for the period from 2–29 May 2022.In terms of the characteristics of systematic bias,both the background and analysis show diurnal bias,and these large biases are affected by complex underlying surfaces(e.g.,oceans,coasts,and mountains).After the application of the SBCS,the results of the data assimilation show that the SBCS can reduce the systematic bias of the background and yield a neutral to slightly positive result for the analysis fields.In addition,the SBCS can reduce forecast errors and improve forecast results,especially for surface variables.The above results indicate that this scheme has good prospects for high-resolution regional NWP models.
基金supported by the National Natural Science Foundation project“Micro-Scale Effect of Oil-Gas Flow and the Mechanism of Enhancing Shale Oil Recovery by Natural Gas Injection”(No.52074317)。
文摘Oilfields worldwide are increasingly grappling with challenges such as early water breakthrough and high water production,yet direct,targeted solutions remain elusive.In recent years,chemical flooding techniques designed for tertiary oil recovery have garnered significant attention,with microgel flooding emerging as a particularly prominent area of research.Despite its promise,the complex mechanisms underlying microgel flooding have been rarely investigated numerically.This study aims to address these gaps by characterizing the distribution of microgel concentration and viscosity within different pore structures.To enhance the accuracy of these characterizations,the viscosity of microgels is adjusted to account for the shear effects induced by flow rate and the swelling effects driven by salinity variations.The absolute permeability of the rock and the relative permeability of both oil and microgel are also analyzed to elucidate the mechanisms of microgel flooding.Additionally,a connectivity model is employed to achieve a quantitative representation of fluid flow capacity.The proposed model is validated through conceptual examples and applied to real oilfield blocks,demonstrating its accuracy and practical applicability.
基金supported by the National Natural Science Foundation of China(52104049)the Young Elite Scientist Sponsorship Program by Beijing Association for Science and Technology(BYESS2023262)。
文摘Polymer flooding is an important means of improving oil recovery and is widely used in Daqing,Xinjiang,and Shengli oilfields,China.Different from conventional injection media such as water and gas,viscoelastic polymer solutions exhibit non-Newtonian and nonlinear flow behavior including shear thinning and shear thickening,polymer convection,diffusion,adsorption,retention,inaccessible pore volume,and reduced effective permeability.However,available well test model of polymer flooding wells generally simplifies these characteristics on pressure transient response,which may lead to inaccurate results.This work proposes a novel two-phase numerical well test model to better describe the polymer viscoelasticity and nonlinear flow behavior.Different influence factors that related to near-well blockage during polymer flooding process,including the degree of blockage(inner zone permeability),the extent of blockage(composite radius),and polymer flooding front radius are explored to investigate these impacts on bottom hole pressure responses.Results show that polymer viscoelasticity has a significant impact on the transitional flow segment of type curves,and the effects of near-well formation blockage and polymer concentration distribution on well test curves are very similar.Thus,to accurately interpret the degree of near-well blockage in injection wells,it is essential to first eliminate the influence of polymer viscoelasticity.Finally,a field case is comprehensively analyzed and discussed to illustrate the applicability of the proposed model.
基金Funded by the National Natural Science Foundation of China Academy of Engineering Physics and Jointly Setup"NSAF"Joint Fund(No.U1430119)。
文摘The multi-scale modeling combined with the cohesive zone model(CZM)and the molecular dynamics(MD)method were preformed to simulate the crack propagation in NiTi shape memory alloys(SMAs).The metallographic microscope and image processing technology were employed to achieve a quantitative grain size distribution of NiTi alloys so as to provide experimental data for molecular dynamics modeling at the atomic scale.Considering the size effect of molecular dynamics model on material properties,a reasonable modeling size was provided by taking into account three characteristic dimensions from the perspective of macro,meso,and micro scales according to the Buckinghamπtheorem.Then,the corresponding MD simulation on deformation and fracture behavior was investigated to derive a parameterized traction-separation(T-S)law,and then it was embedded into cohesive elements of finite element software.Thus,the crack propagation behavior in NiTi alloys was reproduced by the finite element method(FEM).The experimental results show that the predicted initiation fracture toughness is in good agreement with experimental data.In addition,it is found that the dynamics initiation fracture toughness increases with decreasing grain size and increasing loading velocity.
基金supported by the National Natural Science Foundation of China(Grant No.52375340,51975263,52405366).
文摘A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of shielding gases with varying He-Ar ratios,and the coupling between arc plasma and laser-induced metal plume.The accuracy of the model is validated using a high-speed camera.The effects of varying He contents in the shielding gas on both the temperature and flow velocity of hybrid plasma,as well as the distribu-tion of laser-induced metal vapor mass,were investigated separately.The maximum temperature and size of arc plasma decrease as the He volume ratio increases,the arc distribution becomes more concentrated,and its flow velocity initially decreases and then sharply increases.At high helium content,both the flow velocity of hybrid plasma and metal vapor are high,the metal vapor is con-centrated on the right side of keyhole,and its flow appears chaotic.The flow state of arc plasma is most stable when the shielding gas consists of 50%He+50%Ar.
基金financially supported by the National Key Research and Development Program of China(Grant No.2016YFC0402603)the National Natural Science Foundation of China(Grant Nos.51779112,51509119,and 51609029)+2 种基金the Project of Tianjin Natural Science Foundation(Grant No.16JCQNJC06900)the Open Project of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2014492211)the Fundamental Research Funds for the Central Public Welfare Research Institutes(Grant Nos.TKS170101and TKS170202)
文摘A process-based 3D numerical model for surfzone hydrodynamics and beach evolution was established. Comparisons between the experimental data and model results proved that the model could effectively describe the hydrodynamics, sediment transport feature and sandbar migration process in the surfzone with satisfactory precision. A series of numerical simulations on the wave breaking and shoaling up to a barred beach were carried out based on the model system. Analyzed from the model results, the wave-induced current system in the surfzone consists of two major processes, which are the phase-averaged undertow caused by wave breaking and the net drift caused by both of the nonlinear wave motion and surface roller effect. When storm waves come to the barred beach, the strong offshore undertow along the beach suppresses the onshore net drift, making the initial sandbar migrate to the seaside. Under the condition of calm wave environment, both the undertow and net drift flow to the shoreline at the offshore side of the sandbar, and then push the initial sandbar to the shoreline. The consideration of surface roller has significant impact on the modeling results of the sandbar migration. As the roller transfer rate increases, the sandbar moves onshore especially under the storm wave condition.
基金The Open Research Fund of Key Laboratory of Highway Engineering of Sichuan Province of Southw est Jiaotong University (No.LHTE002201102)
文摘In order to investigate the fatigue behavior of asphalt concrete, a new numerical approach based on a bi-linear cohesive zone model （CZM） is developed. Integrated with the CZM, a fatigue damage evolution model is established to indicate the gradual degradation of cohesive properties of asphalt concrete under cyclic loading. Then the model is implemented in the finite element software ABAQUS through a user-defined subroutine. Based on the proposed model, an indirect tensile fatigue test is finally simulated. The fatigue lives obtained through numerical analysis show good agreement with laboratory results. Fatigue damage accumulates in a nonlinear manner during the cyclic loading process and damage initiation phase is the major part of fatigue failure. As the stress ratio increases, the time of the steady damage growth stage decreases significantly. It is found that the proposed fatigue damage evolution model can serve as an accurate and efficient tool for the prediction of fatigue damage of asphalt concrete.
基金National Natural Science Foundation (Project number 40604013).
文摘Biot-flow and squirt-flow are the two most important fluid flow mechanisms in porous media containing fluids. Based on the BISQ （Biot-Squirt） model where the two mechanisms are treated simultaneously, the elastic wave-field simulation in the porous medium is limited to two-dimensions and two-components （2D2C） or two-dimensions and three-components （2D3C）. There is no previous report on wave simulation in three- dimensions and three-components. Only through three dimensional numerical simulations can we have an overall understanding of wave field coupling relations and the spatial distribution characteristics between the solid and fluid phases in the dual-phase anisotropic medium. In this paper, based on the BISQ equation, we present elastic wave propagation in a three dimensional dual-phase anisotropic medium simulated by the staggered-grid high-order finite-difference method. We analyze the resulting wave fields and show that the results are an improvement.
基金supported by the National High Technology Research and Development Program (863 Program)(2009AA06Z108)
文摘To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional （2D） time- domain transient electromagnetic secondary field of the line source based on the DuFort- Frankel finite-difference method. In the proposed method, we included the treatment of the earth-air boundary conductivity, calculated the normalized partial derivative of the induced electromotive force （Emf）, and determined the forward time step. By extending upward the earth-air interface to the air grid nodes and the zero-value boundary conditions, not only we have a method that is more efficient but also simpler than the total field solution. We computed and analyzed the homogeneous half-space model and the fiat layered model with high precision--the maximum relative error is less than 0.01% between our method and the analytical method--and the solution speed is roughly three times faster than the total-field solution. Lastly, we used the model of a thin body embedded in a homogeneous half-space at different delay times to depict the downward and upward spreading characteristics of the induced eddy current, and the physical interaction processes between the electromagnetic field and the underground low-resistivity body.
文摘This study focuses on the factors that may affect the feasibility of performing elliptical anisotropy analysis on azimuthal PP and PS-wave data in HTI media, with the aim of using the modeling results as guidance in real seismic data application. Our results reveal that there is an offset limitation for both PP- and PS-waves in elliptical anisotropy fitting, and that PS-waves show a wider applicable offset range and larger observable azimuthal anisotropy than PP-waves. The major axis of the elliptical fit to the amplitudes of the R-component is perpendicular to the fracture strike, which is opposite to that in PP-wave analysis. The azimuthal interval travel time of PS-waves shows a nearly elliptical distribution and the major axis of the fit ellipse is perpendicular to the fracture strike, which is same as that in PP-wave analysis. For data within the applicable offset range, the anisotropic magnitude obtained from amplitude and travel time attributes of PP- and PS-waves exhibits a dependence on fracture density, and the major to minor axis ratio of the fit ellipse may be used to infer the relative distribution of fracture densities.
文摘In order to reasonably simulate tidal currents around small structures such as piles in a large-scale model domain, a 2-D hydrodynamic integrated model for Bohai Sea is established with the finite element method. The grid can be discretionarily refined as a non-structure triangle or quadrilateral so that piers can be treated as one or several impermeable elements with an area of 20 to 30 km^2 in a model domain over 85 700 km^2. The computational results of tidal levels and horizontal velocities are in good agreement with the field data. Based on the computed results by the model, the layout of an open 105 DWT liquefied natural gas （LNG）terminal in Caofeidian, Bohal Sea is effectively and reasonably optimized. It can be concluded that the model is suitable and reasonable for direct simulation of tidal currents around small structures in projects.
文摘To improve the accuracy of the conventional finite-difference method, finitedifference numerical modeling methods of any even-order accuracy are recommended. We introduce any even-order accuracy difference schemes of any-order derivatives derived from Taylor series expansion. Then, a finite-difference numerical modeling method with any evenorder accuracy is utilized to simulate seismic wave propagation in two-phase anisotropic media. Results indicate that modeling accuracy improves with the increase of difference accuracy order number. It is essential to find the optimal order number, grid size, and time step to balance modeling precision and computational complexity. Four kinds of waves, static mode in the source point, SV wave cusps, reflection and transmission waves are observed in two-phase anisotropic media through modeling.
文摘Haihua Islands is a large artificial island in Danzhou, Hainan. The construction of Haihua Islands changes the hYdrodynamic environment of Yangpu waters, and further affects its morphological change. Delft3D is used to set up a two dimensional nested hydrodynamic and sediment model for Yangpu waters in this paper, and this paper focuses on simulating the velocity and morphological change due to the construction of Haihua Islands after the verification of the model. The seabed deposition is small because of low suspended sediment concentration and less sand source near Yangpu waters. The bed level erodes in the south area of Xiaochan Reef and the Yangpu channel due to the velocity increase in the area.
文摘A mathematical model of resin flow and temperature variation in the filling stage of the resin transfer molding (RTM) is developed based on the control volume/finite element method (CV/FEM). The effects of the heat transfer and chemical reaction of the resin on the flow and temperature are considered. The numerical algorithm of the resin flow and temperature variation in the process of RTM are studied. Its accuracy and convergence are analyzed. The comparison of temperature variations between experimental results and model predictions is carried out for two RTM cases. Result shows that the model is efficient for evaluating the flow and temperature variation in the filling stage of RTM and there is a good coincidence between theory and experiment.
基金Project(2009ZX04004-031-04) supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China
文摘Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the investigated powder Distaloy AE were determined as functions of relative density through typical mechanical property tests of powder. The model was implemented as a user subroutine USDFLD. Single sided compaction of a d20 ram^5 mm disk green compact of Distaloy AE was simulated, and the residual stress of the disk after ejection was predicted with FEA. The FEA results of the compaction process and the residual stress of the disk show good agreement with compaction experiments and X-ray diffraction measurements, which validates the model and its parameters. The results indicate that the compressive residual stresses exist mainly in a thin layer on the side surface, but the residual stresses are very small on the top and bottom surfaces.
基金supported by the National Key R&D Program of China(Grant No.2017YFC1502202)the National Science Foundation of China(Grant Nos.41675075 and41875135)the National Key R&D Program of China(Grant No.2016YFA0602101)
文摘This review summarizes the scientific and technical progress in atmospheric modeling in China since 2011,including the dynamical core,model physics,data assimilation,ensemble forecasting,and model evaluation strategies.In terms of the dynamical core,important efforts have been made in the improvement of the existing model formulations and in exploring new modeling approaches that can better adapt to massively parallel computers and global multiscale modeling.With regard to model physics,various achievements in physical representations have been made,especially a trend toward scale-aware parameterization for accommodating the increase of model resolution.In the field of data assimilation,a 4D-Var system has been developed and is operationally used by the National Meteorological Center of China,and its performance is promising.Furthermore,ensemble forecasting has played a more important role in operational forecast systems and progressed in many fundamental techniques.Model evaluation strategies,including key performance metrics and standardized experimental protocols,have been proposed and widely applied to better understand the strengths and weaknesses of the systems,offering key routes for model improvement.The paper concludes with a concise summary of the status quo and a brief outlook in terms of future development.
