This study aims to develop a chloride diffusion simulation method that considers the hydration microstructure and pore solution properties during the hydration of tricalcium silicate(C3S).The method combines the hydra...This study aims to develop a chloride diffusion simulation method that considers the hydration microstructure and pore solution properties during the hydration of tricalcium silicate(C3S).The method combines the hydration simulation,thermodynamic calculation,and finite element analysis to examine the effects of pore solution,including effect of electrochemical potential,effect of chemical activity,and effect of mechanical interactions between ions,on the chloride effective diffusion coefficient of hydrated C3S paste.The results indicate that the effect of electrochemical potential on chloride diffusion becomes stronger with increasing hydration age due to the increase in the content of hydrated calcium silicate;as the hydration age increases,the effect of chemical activity on chloride diffusion weakens when the number of diffusible elements decreases;the effect of mechanical interactions between ions on chloride diffusion decreases with the increase of hydration age.展开更多
Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) io...Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) ion sources.With this in mind, to measure the emittance of the ion beams produced by the mVINIS ECR, which is part of the FAMA facility at the Vin?a Institute of Nuclear Sciences, we have developed a pepper-pot scintillator screen system combined with a CMOS camera. The application, developed on the Lab VIEW platform, allows us to control the camera's main attribute settings, such as the shutter speed and the gain, record the images in the region of interest, and process and filter the images in real time. To analyze the data from the obtained image, we have developed an algorithm called measurement and analysis of ion beam luminosity(MAIBL) to reconstruct the four-dimensional(4D) beam profile and calculate the root mean square(RMS) emittance. Before measuring emittance, we performed a simulated experiment using the pepper-pot simulation(PPS) program. An exported file(PPS) gives a numerically generated raw image(mock image) of a beam with a predefined emittance value after it has passed through a pepper-pot mask. By analyzing data from mock images instead of the image obtained by the camera and putting it into the MAIBL algorithm, we can compare the calculated emittance with PPS's initial emittance value. In this paper, we present our computational tools and explain the method for verifying the correctness of the calculated emittance values.展开更多
A 3-D digital core describes the pore space microstructure of rocks. An X-ray micro CT scan is the most accurate and direct but costly method to obtain a 3-D digital core. In this study, we propose a hybrid method whi...A 3-D digital core describes the pore space microstructure of rocks. An X-ray micro CT scan is the most accurate and direct but costly method to obtain a 3-D digital core. In this study, we propose a hybrid method which combines sedimentation simulation and simulated annealing （SA） method to generate 3-D digital cores based on 2-D images of rocks. The method starts with the sedimentation simulation to build a 3-D digital core, which is the initial configuration for the SA method. We update the initial digital core using the SA method to match the auto-correlation function of the 2-D rock image and eventually build the final 3-D digital core. Compared with the typical SA method, the hybrid method has significantly reduced the computation time. Local porosity theory is applied to quantitatively compare the reconstructed 3-D digital cores with the X-ray micro CT 3-D images. The results indicate that the 3-D digital cores reconstructed by the hybrid method have homogeneity and geometric connectivity similar to those of the X-ray micro CT image. The formation factors and permeabilities of the reconstructed 3-D digital cores are estimated using the finite element method （FEM） and lattice Boltzmann method （LBM）, respectively. The simulated results are in good agreement with the experimental measurements. Comparison of the simulation results suggests that the digital cores reconstructed by the hybrid method more closely reflect the true transport properties than the typical SA method alone.展开更多
It is difficult to temporally and spatially track and characterize the slurry viscosity in flowing water during grouting simulation.In this study,a sequential flow and solidification(SFS)method considering the spatial...It is difficult to temporally and spatially track and characterize the slurry viscosity in flowing water during grouting simulation.In this study,a sequential flow and solidification(SFS)method considering the spatial-temporal evolution of slurry viscosity in flowing water in karst conduit is proposed.First,a time-dependent model for the threshold function of slurry viscosity is established.During the grouting process,the spatial-temporal evolution of slurry viscosity is revealed by tracking the diffusion behavior of the slurry injected at different times.This method is capable of describing the gradual solidification process of the slurry during grouting.Furthermore,a physical model of grouting in a karst conduit is developed.Second,the effectiveness of the SFS method in grouting simulation is verified by the experiment of grouting conduit in flowing water.The SFS method enables real-time monitoring of fluid velocity and pressure during grouting in flowing water and provides a feasible calculation method for revealing the grouting plugging mechanism in complex karst conduits at different engineering scales.In addition,it can be used to guide the design of grouting tests in flowing water,improve cost efficiency,and provide theoretical basis for optimizing grouting design and slurry selection.展开更多
The particle simulation method is used to study the effects of loading waveforms （i.e. square, sinusoidal and triangle waveforms） on rock damage at mesoscopic scale. Then some influencing factors on rock damage at t...The particle simulation method is used to study the effects of loading waveforms （i.e. square, sinusoidal and triangle waveforms） on rock damage at mesoscopic scale. Then some influencing factors on rock damage at the mesoscopic scale, such as loading frequency, stress amplitude, mean stress, confining pressure and loading sequence, are also investigated with sinusoidal waveform in detail. The related numerical results have demonstrated that： 1） the loading waveform has a certain effect on rock failure processes. The square waveform has the most damage within these waveforms, while the triangle waveform has less damage than sinusoidal waveform. In each cycle, the number of microscopic cracks increases in the loading stage, while it keeps nearly constant in the unloading stage. 2） The loading frequency, stress amplitude, mean stress, confining pressure and loading sequence have considerable effects on rock damage subjected to cyclic loading. The higher the loading frequency, stress amplitude and mean stress, the greater the damage the rock accumulated; in contrast, the lower the confining pressure, the greater the damage the rock has accumulated. 3） There is a threshold value of mean stress and stress amplitude, below which no further damage accumulated after the first few cycle loadings. 4） The high-to-low loading sequence has more damage than the low-to-high loading sequence, suggesting that the rock damage is loading-path dependent.展开更多
One of the most critical and complicated steps in mine design is a selection of suitable mining method based upon geological,geotechnical,geographical,safety and economical parameters.The aim of this study is developi...One of the most critical and complicated steps in mine design is a selection of suitable mining method based upon geological,geotechnical,geographical,safety and economical parameters.The aim of this study is developing a Monte Carlo simulation to selection the optimum mining method by using effective and major criteria and at the same time,taking subjective judgments of decision makers into consideration.Proposed approach is based on the combination of Monte Carlo simulation with conventional Analytic Hierarchy Process(AHP).Monte Carlo simulation is used to determine the confdence level of each alternative’s score,is calculated by AHP,with the respect to the variance of decision makers’opinion.The proposed method is applied for Jajarm Bauxite Mine in Iran and eventually the most appropriate mining methods for this mine are ranked.展开更多
The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,igno...The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,ignoring the influence of multiple motion units and the differences in various features among them,which strongly affect the efficiency and accuracy of the simulations.In this study,we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process.CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action method,and the key meta-actions are identified as the nodes in the flow field simulation.We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results.Compared to traditional simulation methods and real measurements,the simulation method provides advantages in terms of simulation efficiency and accuracy.展开更多
This paper presents a rapid and simple risk calculation method for large and complex engineering systems, the simulated maximum entropy method （SMEM）, which is based on integration of the advantages of the Monte Car...This paper presents a rapid and simple risk calculation method for large and complex engineering systems, the simulated maximum entropy method （SMEM）, which is based on integration of the advantages of the Monte Carlo and maximum entropy methods, thus avoiding the shortcoming of the slow convergence rate of the Monte Carlo method in risk calculation. Application of SMEM in the calculation of reservoir flood discharge risk shows that this method can make full use of the known information under the same conditions and obtain the corresponding probability distribution and the risk value. It not only greatly improves the speed, compared with the Monte Carlo method, but also provides a new approach for the risk calculation in large and complex engineering systems.展开更多
A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulat...A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulation method controls the six degrees of freedom of the impeller using the user-defined functions(UDF)program so that it can only rotate under the impact of fluid.The impeller speed can be calculated in real-time,and the inlet speed can be set with time to obtain the dynamic performance of the turbine flow sensors.Based on this simulation method,three turbine flow sensors with different diameters were simulated,and the reliability of the simulation method was verified by both steady-state and unsteady-state experiments.The results show that the trend of meter factor with flow rate acquired from the simulation is close to the experimental results.The deviation between the simulation and experiment results is low,with a maximum deviation of 2.88%.In the unsteady simulation study,the impeller speed changed with the inlet velocity of the turbine flow sensor,showing good tracking performance.The passive simulation method can be used to predict the dynamic performance of the turbine flow sensor.展开更多
To overcome the default of single search tendency, the ants in the colony are divided into several sub-groups. The ants in different subgroups have different trail information and expectation coefficients. The simulat...To overcome the default of single search tendency, the ants in the colony are divided into several sub-groups. The ants in different subgroups have different trail information and expectation coefficients. The simulated annealing method is introduced to the algorithm. Through setting the temperature changing with the iterations, after each turn of tours, the solution set obtained by the ants is taken as the candidate set. The update set is obtained by adding the solutions in the candidate set to the previous update set with the probability determined by the temperature. The solutions in the candidate set are used to update the trail information. In each turn of updating, the current best solution is also used to enhance the trail information on the current best route. The trail information is reset when the algorithm is in stagnation state. The computer experiments demonstrate that the proposed algorithm has higher stability and convergence speed.展开更多
Interfacial heat transfer behavior between the molten steel and twin-rolls is a key issue in the strip casting process,and it has already attracted wide attention from industrial and academic communities of steel.The ...Interfacial heat transfer behavior between the molten steel and twin-rolls is a key issue in the strip casting process,and it has already attracted wide attention from industrial and academic communities of steel.The research methods and influencing factors on the interfacial heat transfer were summarized.Numerical simulation models,semi-industrial scale,and laboratory equipment have been developed in this field,and these methods were also improved by worldwide researchers based on the development of computer,automatic,and visual technologies.Coating properties,naturally deposited film,and casting parameters are the main factors which affect the heat transfer significantly.Although lots of research has been carried out,the internal relations among these influencing factors,interfacial heat transfer,and the quality of the strip are still worth to be further explored.Keywords Strip casting Interfacial heat transfer Simulation method Coating property Naturally deposited film Casting parameter.展开更多
The investigation was carried out on the technical problems of finishing the inner surface of elbow parts and the action mechanism of particles in elbow precision machining by abrasive flow.This work was analyzed and ...The investigation was carried out on the technical problems of finishing the inner surface of elbow parts and the action mechanism of particles in elbow precision machining by abrasive flow.This work was analyzed and researched by combining theory,numerical and experimental methods.The direct simulation Monte Carlo(DSMC)method and the finite element analysis method were combined to reveal the random collision of particles during the precision machining of abrasive flow.Under different inlet velocity,volume fraction and abrasive particle size,the dynamic pressure and turbulence flow energy of abrasive flow in elbow were analyzed,and the machining mechanism of particles on the wall and the influence of different machining parameters on the precision machining quality of abrasive flow were obtained.The test results show the order of the influence of different parameters on the quality of abrasive flow precision machining and establish the optimal process parameters.The results of the surface morphology before and after the precision machining of the inner surface of the elbow are discussed,and the surface roughness Ra value is reduced from 1.125μm to 0.295μm after the precision machining of the abrasive flow.The application of DSMC method provides special insights for the development of abrasive flow technology.展开更多
In this paper .fatigue strength of T-type tubularjoints subjected to in-planebending or out-of-plane bending load is investigated By, considering material constantsand initial crack sizes as random variables and appl...In this paper .fatigue strength of T-type tubularjoints subjected to in-planebending or out-of-plane bending load is investigated By, considering material constantsand initial crack sizes as random variables and applying Monte Carlo simulation method, we have giyen a statistical analvsis on fatigue life. Simultaneously, linearregression analyses of computed resuldts are performed and compared with that of theknown experimental data.展开更多
An element-free Galerkin method(EFGM) is used to solve the two-dimensional(2D) ground penetrating radar(GPR)modelling problems, due to its simple pre-processing, the absence of elements and high accuracy. Different fr...An element-free Galerkin method(EFGM) is used to solve the two-dimensional(2D) ground penetrating radar(GPR)modelling problems, due to its simple pre-processing, the absence of elements and high accuracy. Different from element-based numerical methods, this approach makes nodes free from the elemental restraint and avoids the explicit mesh discretization. First, we derived the boundary value problem for the 2D GPR simulation problems. Second, a penalty function approach and a boundary condition truncated method were used to enforce the essential and the absorbing boundary conditions, respectively. A three-layered GPR model was used to verify our element-free approach. The numerical solutions show that our solutions have an excellent agreement with solutions of a finite element method(FEM). Then, we used the EFGM to simulate one more complex model to show its capability and limitations. Simulation results show that one obvious advantage of EFGM is the absence of element mesh, which makes the method very flexible. Due to the use of MLS fitting, a key feature of EFM, is that both the dependent variable and its gradient are continuous and have high precision.展开更多
For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is develo...For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.展开更多
[ Objective] The research aimed to study simulated method on the release of sediment pollutants in the Temple Lake. [ Method] For existing pollution status of the Temple Lake, sediments and overlying water were sample...[ Objective] The research aimed to study simulated method on the release of sediment pollutants in the Temple Lake. [ Method] For existing pollution status of the Temple Lake, sediments and overlying water were sampled by the integrated device. Based on the technical route, through the orthogonal test, release processes of nitrogen and phosphorus from sediment were simulated, and their release speeds were estimated under different temperatures, pH and DO in the laboratory. Relationship between environmental factor and pollutant release was explored. [ Result] The integrated device of sediment sampling and test had simple structure, cheap cost and easy operation, and sediment pollution test could be conducted without disturbing sediment after collecting sediment. Among the studied three impact factors, temperature had the maximum influence on contaminant release process, which should be considered as the important factor of future research. [ Conclusion] Compared with routine research method of sediment contaminant release from other lakes, simulated method of contaminant release from sediment in the Temple Lake had many advantaqes, which was favorable for scientific research in latter period and actual lake control.展开更多
The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experi...The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.展开更多
Accurate thermal simulation is the key in the simulation approach to defining the unique microstructure and properties of the HAZ regions. Simulation enables an expansion of the volume of material char- acteristic...Accurate thermal simulation is the key in the simulation approach to defining the unique microstructure and properties of the HAZ regions. Simulation enables an expansion of the volume of material char- acteristic of each H4Z region to a sufficient size for property determination.The combined influence of heat input,preheat temperature, plate thickness, and widing process on HAZ microstructure and properties relics on the accurate simulation of thermal cycles corresponding to different peak temperatures using an HAZ simulator like the Gleeble.Several computer programs have been developed to predict thermal excursions in various HAZ regions during welding. Some were developed based simply on the thermal propertics of a material;whereas, others were generated on the basis of actual experimental data.A suitable HAZ thermal simulation program must be ons that can authntically duplicate an ac- tual thermal cycle experienced during welding within reasonable limies. Therefore, the similarities and differences among the HAZ thermal cycles predicted by various methodologies should be fully under- stood. A total of sts thermal cycle prediction methodologies were compared in this evaluation. It was de- termined that some HAZ simulation programs have sever limitations due to the idealized assumptions considered in their development.According to the experieare at The University of Tennessee and the comparison results in this study, the HAZ thermal simulation programs; ' HAZ Calculator' and F(s, d); are recommended for accurate HAZ thermal cycle duplication.展开更多
To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based...To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based on the Soil Conservation Service curve number(SCS-CN) method. Parameters of the model were selected and determined according to the comprehensive analysis of model evaluation indexes. The first simulation of forest reconstruction scenario,namely a coniferous forest covering 59.35km^2 is replaced by a broad-leaved forest showed no significant impact on the flood reduction in the URTR. The second simulation was added with 61.75km^2 bamboo forest replaced by broad-leaved forest,the reduction of flood peak discharge and flood volume could be improved significantly. Specifically,flood peak discharge of 10-year return period event was reduced to 7-year event,and the reduction rate of small flood was 21%-28%. Moreover,the flood volume was reduced by 9%-14% and 18%-35% for moderate floods and small floods,respectively. The resultssuggest that the bamboo forest reconstruction is an effective control solution for small to moderate flood in the URTR,the effect of forest conversion on flood volume is increasingly reduced as the rainfall amount increases to more extreme magnitude. Using a hydrological model with scenarios analysis is an effective simulation approach in investigating the relationship between forest type change and flood control. This method would provide reliable support for flood control and disaster mitigation in mountainous cities.展开更多
Hydraulic fracturing （HF） technique has been extensively used for the exploitation of unconventional oiland gas reservoirs. HF enhances the connectivity of less permeable oil and gas-bearing rock formationsby fluid ...Hydraulic fracturing （HF） technique has been extensively used for the exploitation of unconventional oiland gas reservoirs. HF enhances the connectivity of less permeable oil and gas-bearing rock formationsby fluid injection, which creates an interconnected fracture network and increases the hydrocarbonproduction. Meanwhile, microseismic （MS） monitoring is one of the most effective approaches to evaluatesuch stimulation process. In this paper, the combined finite-discrete element method （FDEM） isadopted to numerically simulate HF and associated MS. Several post-processing tools, includingfrequency-magnitude distribution （b-value）, fractal dimension （D-value）, and seismic events clustering,are utilized to interpret numerical results. A non-parametric clustering algorithm designed specificallyfor FDEM is used to reduce the mesh dependency and extract more realistic seismic information.Simulation results indicated that at the local scale, the HF process tends to propagate following the rockmass discontinuities; while at the reservoir scale, it tends to develop in the direction parallel to themaximum in-situ stress. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20241529)China Postdoctoral Science Foundation(No.2024M750736)。
文摘This study aims to develop a chloride diffusion simulation method that considers the hydration microstructure and pore solution properties during the hydration of tricalcium silicate(C3S).The method combines the hydration simulation,thermodynamic calculation,and finite element analysis to examine the effects of pore solution,including effect of electrochemical potential,effect of chemical activity,and effect of mechanical interactions between ions,on the chloride effective diffusion coefficient of hydrated C3S paste.The results indicate that the effect of electrochemical potential on chloride diffusion becomes stronger with increasing hydration age due to the increase in the content of hydrated calcium silicate;as the hydration age increases,the effect of chemical activity on chloride diffusion weakens when the number of diffusible elements decreases;the effect of mechanical interactions between ions on chloride diffusion decreases with the increase of hydration age.
基金funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia via the FAMA project (research topic “Physics and chemistry with ion beams”)。
文摘Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) ion sources.With this in mind, to measure the emittance of the ion beams produced by the mVINIS ECR, which is part of the FAMA facility at the Vin?a Institute of Nuclear Sciences, we have developed a pepper-pot scintillator screen system combined with a CMOS camera. The application, developed on the Lab VIEW platform, allows us to control the camera's main attribute settings, such as the shutter speed and the gain, record the images in the region of interest, and process and filter the images in real time. To analyze the data from the obtained image, we have developed an algorithm called measurement and analysis of ion beam luminosity(MAIBL) to reconstruct the four-dimensional(4D) beam profile and calculate the root mean square(RMS) emittance. Before measuring emittance, we performed a simulated experiment using the pepper-pot simulation(PPS) program. An exported file(PPS) gives a numerically generated raw image(mock image) of a beam with a predefined emittance value after it has passed through a pepper-pot mask. By analyzing data from mock images instead of the image obtained by the camera and putting it into the MAIBL algorithm, we can compare the calculated emittance with PPS's initial emittance value. In this paper, we present our computational tools and explain the method for verifying the correctness of the calculated emittance values.
基金sponsored by NSFC(Grant No.40574030)CNPC Research Project(Grant No.06A30102)
文摘A 3-D digital core describes the pore space microstructure of rocks. An X-ray micro CT scan is the most accurate and direct but costly method to obtain a 3-D digital core. In this study, we propose a hybrid method which combines sedimentation simulation and simulated annealing （SA） method to generate 3-D digital cores based on 2-D images of rocks. The method starts with the sedimentation simulation to build a 3-D digital core, which is the initial configuration for the SA method. We update the initial digital core using the SA method to match the auto-correlation function of the 2-D rock image and eventually build the final 3-D digital core. Compared with the typical SA method, the hybrid method has significantly reduced the computation time. Local porosity theory is applied to quantitatively compare the reconstructed 3-D digital cores with the X-ray micro CT 3-D images. The results indicate that the 3-D digital cores reconstructed by the hybrid method have homogeneity and geometric connectivity similar to those of the X-ray micro CT image. The formation factors and permeabilities of the reconstructed 3-D digital cores are estimated using the finite element method （FEM） and lattice Boltzmann method （LBM）, respectively. The simulated results are in good agreement with the experimental measurements. Comparison of the simulation results suggests that the digital cores reconstructed by the hybrid method more closely reflect the true transport properties than the typical SA method alone.
基金financial support from the National Natural Science Foundation of China(Grant Nos.52022053 and 51879153)the China National Postdoctoral Program for Innovative Talents(Grant No.BX2021172)。
文摘It is difficult to temporally and spatially track and characterize the slurry viscosity in flowing water during grouting simulation.In this study,a sequential flow and solidification(SFS)method considering the spatial-temporal evolution of slurry viscosity in flowing water in karst conduit is proposed.First,a time-dependent model for the threshold function of slurry viscosity is established.During the grouting process,the spatial-temporal evolution of slurry viscosity is revealed by tracking the diffusion behavior of the slurry injected at different times.This method is capable of describing the gradual solidification process of the slurry during grouting.Furthermore,a physical model of grouting in a karst conduit is developed.Second,the effectiveness of the SFS method in grouting simulation is verified by the experiment of grouting conduit in flowing water.The SFS method enables real-time monitoring of fluid velocity and pressure during grouting in flowing water and provides a feasible calculation method for revealing the grouting plugging mechanism in complex karst conduits at different engineering scales.In addition,it can be used to guide the design of grouting tests in flowing water,improve cost efficiency,and provide theoretical basis for optimizing grouting design and slurry selection.
基金Projects(11702235,51641905,41472269) supported by the National Natural Science Foundation of ChinaProject(2017JJ3290) supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(17C1540) supported by the Scientific Research Foundation of Education Department of Hunan Province,ChinaProject(16GES07) supported by the Open Research Fund of Hunan Key Laboratory of Geomechanics and Engineering Safety,China
文摘The particle simulation method is used to study the effects of loading waveforms （i.e. square, sinusoidal and triangle waveforms） on rock damage at mesoscopic scale. Then some influencing factors on rock damage at the mesoscopic scale, such as loading frequency, stress amplitude, mean stress, confining pressure and loading sequence, are also investigated with sinusoidal waveform in detail. The related numerical results have demonstrated that： 1） the loading waveform has a certain effect on rock failure processes. The square waveform has the most damage within these waveforms, while the triangle waveform has less damage than sinusoidal waveform. In each cycle, the number of microscopic cracks increases in the loading stage, while it keeps nearly constant in the unloading stage. 2） The loading frequency, stress amplitude, mean stress, confining pressure and loading sequence have considerable effects on rock damage subjected to cyclic loading. The higher the loading frequency, stress amplitude and mean stress, the greater the damage the rock accumulated; in contrast, the lower the confining pressure, the greater the damage the rock has accumulated. 3） There is a threshold value of mean stress and stress amplitude, below which no further damage accumulated after the first few cycle loadings. 4） The high-to-low loading sequence has more damage than the low-to-high loading sequence, suggesting that the rock damage is loading-path dependent.
文摘One of the most critical and complicated steps in mine design is a selection of suitable mining method based upon geological,geotechnical,geographical,safety and economical parameters.The aim of this study is developing a Monte Carlo simulation to selection the optimum mining method by using effective and major criteria and at the same time,taking subjective judgments of decision makers into consideration.Proposed approach is based on the combination of Monte Carlo simulation with conventional Analytic Hierarchy Process(AHP).Monte Carlo simulation is used to determine the confdence level of each alternative’s score,is calculated by AHP,with the respect to the variance of decision makers’opinion.The proposed method is applied for Jajarm Bauxite Mine in Iran and eventually the most appropriate mining methods for this mine are ranked.
基金supported by the National Natural Science Foundation of China (No. 52075350)the Special City School Strategic Cooperation Project of Sichuan University and Zigong (No.2021CDZG-3)
文摘The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,ignoring the influence of multiple motion units and the differences in various features among them,which strongly affect the efficiency and accuracy of the simulations.In this study,we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process.CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action method,and the key meta-actions are identified as the nodes in the flow field simulation.We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results.Compared to traditional simulation methods and real measurements,the simulation method provides advantages in terms of simulation efficiency and accuracy.
基金supported by the National Water Pollution Control and Management Technology Major Projects(Grant No. 2009ZX07423-001)the National Natural Science Foundation of China (Grants No.51179069and 40971300)the Fundamental Research Funds for the Central Universities (Grants No.10QX43,09MG16,and 10QG23)
文摘This paper presents a rapid and simple risk calculation method for large and complex engineering systems, the simulated maximum entropy method （SMEM）, which is based on integration of the advantages of the Monte Carlo and maximum entropy methods, thus avoiding the shortcoming of the slow convergence rate of the Monte Carlo method in risk calculation. Application of SMEM in the calculation of reservoir flood discharge risk shows that this method can make full use of the known information under the same conditions and obtain the corresponding probability distribution and the risk value. It not only greatly improves the speed, compared with the Monte Carlo method, but also provides a new approach for the risk calculation in large and complex engineering systems.
基金The National Natural Science Foundation of China(No.62173122)the Hebei Key Project of Natural Science Foundation(No.F2021201031)。
文摘A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulation method controls the six degrees of freedom of the impeller using the user-defined functions(UDF)program so that it can only rotate under the impact of fluid.The impeller speed can be calculated in real-time,and the inlet speed can be set with time to obtain the dynamic performance of the turbine flow sensors.Based on this simulation method,three turbine flow sensors with different diameters were simulated,and the reliability of the simulation method was verified by both steady-state and unsteady-state experiments.The results show that the trend of meter factor with flow rate acquired from the simulation is close to the experimental results.The deviation between the simulation and experiment results is low,with a maximum deviation of 2.88%.In the unsteady simulation study,the impeller speed changed with the inlet velocity of the turbine flow sensor,showing good tracking performance.The passive simulation method can be used to predict the dynamic performance of the turbine flow sensor.
基金Project supported by the National Natural Science Foundation of China (Grant No.50608069)
文摘To overcome the default of single search tendency, the ants in the colony are divided into several sub-groups. The ants in different subgroups have different trail information and expectation coefficients. The simulated annealing method is introduced to the algorithm. Through setting the temperature changing with the iterations, after each turn of tours, the solution set obtained by the ants is taken as the candidate set. The update set is obtained by adding the solutions in the candidate set to the previous update set with the probability determined by the temperature. The solutions in the candidate set are used to update the trail information. In each turn of updating, the current best solution is also used to enhance the trail information on the current best route. The trail information is reset when the algorithm is in stagnation state. The computer experiments demonstrate that the proposed algorithm has higher stability and convergence speed.
基金The financial support from Hunan Scientific Technology Projects(Grant Nos.2020WK2003 and 2019RS3007)National Natural Science Foundation of China(Grant Nos.52130408 and U1760202)is gratefully acknowledged.
文摘Interfacial heat transfer behavior between the molten steel and twin-rolls is a key issue in the strip casting process,and it has already attracted wide attention from industrial and academic communities of steel.The research methods and influencing factors on the interfacial heat transfer were summarized.Numerical simulation models,semi-industrial scale,and laboratory equipment have been developed in this field,and these methods were also improved by worldwide researchers based on the development of computer,automatic,and visual technologies.Coating properties,naturally deposited film,and casting parameters are the main factors which affect the heat transfer significantly.Although lots of research has been carried out,the internal relations among these influencing factors,interfacial heat transfer,and the quality of the strip are still worth to be further explored.Keywords Strip casting Interfacial heat transfer Simulation method Coating property Naturally deposited film Casting parameter.
基金Projects(51206011,U1937201)supported by the National Natural Science Foundation of ChinaProject(20200301040RQ)supported by the Science and Technology Development Program of Jilin Province,China+1 种基金Project(JJKH20190541KJ)supported by the Education Department of Jilin Province,ChinaProject(18DY017)supported by Changchun Science and Technology Program of Changchun City,China。
文摘The investigation was carried out on the technical problems of finishing the inner surface of elbow parts and the action mechanism of particles in elbow precision machining by abrasive flow.This work was analyzed and researched by combining theory,numerical and experimental methods.The direct simulation Monte Carlo(DSMC)method and the finite element analysis method were combined to reveal the random collision of particles during the precision machining of abrasive flow.Under different inlet velocity,volume fraction and abrasive particle size,the dynamic pressure and turbulence flow energy of abrasive flow in elbow were analyzed,and the machining mechanism of particles on the wall and the influence of different machining parameters on the precision machining quality of abrasive flow were obtained.The test results show the order of the influence of different parameters on the quality of abrasive flow precision machining and establish the optimal process parameters.The results of the surface morphology before and after the precision machining of the inner surface of the elbow are discussed,and the surface roughness Ra value is reduced from 1.125μm to 0.295μm after the precision machining of the abrasive flow.The application of DSMC method provides special insights for the development of abrasive flow technology.
文摘In this paper .fatigue strength of T-type tubularjoints subjected to in-planebending or out-of-plane bending load is investigated By, considering material constantsand initial crack sizes as random variables and applying Monte Carlo simulation method, we have giyen a statistical analvsis on fatigue life. Simultaneously, linearregression analyses of computed resuldts are performed and compared with that of theknown experimental data.
基金Project(41074085)supported by the National Natural Science Foundation of ChinaProject(NCET-12-0551)supported by the Funds for New Century Excellent Talents in University,ChinaProject supported by Shenghua Yuying Program of Central South University,China
文摘An element-free Galerkin method(EFGM) is used to solve the two-dimensional(2D) ground penetrating radar(GPR)modelling problems, due to its simple pre-processing, the absence of elements and high accuracy. Different from element-based numerical methods, this approach makes nodes free from the elemental restraint and avoids the explicit mesh discretization. First, we derived the boundary value problem for the 2D GPR simulation problems. Second, a penalty function approach and a boundary condition truncated method were used to enforce the essential and the absorbing boundary conditions, respectively. A three-layered GPR model was used to verify our element-free approach. The numerical solutions show that our solutions have an excellent agreement with solutions of a finite element method(FEM). Then, we used the EFGM to simulate one more complex model to show its capability and limitations. Simulation results show that one obvious advantage of EFGM is the absence of element mesh, which makes the method very flexible. Due to the use of MLS fitting, a key feature of EFM, is that both the dependent variable and its gradient are continuous and have high precision.
基金financially supported by the Program for New Century Excellent Talents in University(No.NCET-13-0229,NCET-09-0396)the National Science & Technology Key Projects of Numerical Control(No.2012ZX04010-031,2012ZX0412-011)the National High Technology Research and Development Program("863"Program)of China(No.2013031003)
文摘For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.
基金Supported by the Item of Wuhan Science and Technology Bureau,China
文摘[ Objective] The research aimed to study simulated method on the release of sediment pollutants in the Temple Lake. [ Method] For existing pollution status of the Temple Lake, sediments and overlying water were sampled by the integrated device. Based on the technical route, through the orthogonal test, release processes of nitrogen and phosphorus from sediment were simulated, and their release speeds were estimated under different temperatures, pH and DO in the laboratory. Relationship between environmental factor and pollutant release was explored. [ Result] The integrated device of sediment sampling and test had simple structure, cheap cost and easy operation, and sediment pollution test could be conducted without disturbing sediment after collecting sediment. Among the studied three impact factors, temperature had the maximum influence on contaminant release process, which should be considered as the important factor of future research. [ Conclusion] Compared with routine research method of sediment contaminant release from other lakes, simulated method of contaminant release from sediment in the Temple Lake had many advantaqes, which was favorable for scientific research in latter period and actual lake control.
基金supported by National Natural Science Foundation of China(Nos.92066108 and 51277061)。
文摘The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.
文摘Accurate thermal simulation is the key in the simulation approach to defining the unique microstructure and properties of the HAZ regions. Simulation enables an expansion of the volume of material char- acteristic of each H4Z region to a sufficient size for property determination.The combined influence of heat input,preheat temperature, plate thickness, and widing process on HAZ microstructure and properties relics on the accurate simulation of thermal cycles corresponding to different peak temperatures using an HAZ simulator like the Gleeble.Several computer programs have been developed to predict thermal excursions in various HAZ regions during welding. Some were developed based simply on the thermal propertics of a material;whereas, others were generated on the basis of actual experimental data.A suitable HAZ thermal simulation program must be ons that can authntically duplicate an ac- tual thermal cycle experienced during welding within reasonable limies. Therefore, the similarities and differences among the HAZ thermal cycles predicted by various methodologies should be fully under- stood. A total of sts thermal cycle prediction methodologies were compared in this evaluation. It was de- termined that some HAZ simulation programs have sever limitations due to the idealized assumptions considered in their development.According to the experieare at The University of Tennessee and the comparison results in this study, the HAZ thermal simulation programs; ' HAZ Calculator' and F(s, d); are recommended for accurate HAZ thermal cycle duplication.
基金funded by the National Natural Science Foundation of China (Grants No.51278239)
文摘To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based on the Soil Conservation Service curve number(SCS-CN) method. Parameters of the model were selected and determined according to the comprehensive analysis of model evaluation indexes. The first simulation of forest reconstruction scenario,namely a coniferous forest covering 59.35km^2 is replaced by a broad-leaved forest showed no significant impact on the flood reduction in the URTR. The second simulation was added with 61.75km^2 bamboo forest replaced by broad-leaved forest,the reduction of flood peak discharge and flood volume could be improved significantly. Specifically,flood peak discharge of 10-year return period event was reduced to 7-year event,and the reduction rate of small flood was 21%-28%. Moreover,the flood volume was reduced by 9%-14% and 18%-35% for moderate floods and small floods,respectively. The resultssuggest that the bamboo forest reconstruction is an effective control solution for small to moderate flood in the URTR,the effect of forest conversion on flood volume is increasingly reduced as the rainfall amount increases to more extreme magnitude. Using a hydrological model with scenarios analysis is an effective simulation approach in investigating the relationship between forest type change and flood control. This method would provide reliable support for flood control and disaster mitigation in mountainous cities.
基金supported by the Natural Sciences and Engineering Research Council of Canada through Discovery Grant 341275 (G. Grasselli) and Engage EGP 461019-13
文摘Hydraulic fracturing （HF） technique has been extensively used for the exploitation of unconventional oiland gas reservoirs. HF enhances the connectivity of less permeable oil and gas-bearing rock formationsby fluid injection, which creates an interconnected fracture network and increases the hydrocarbonproduction. Meanwhile, microseismic （MS） monitoring is one of the most effective approaches to evaluatesuch stimulation process. In this paper, the combined finite-discrete element method （FDEM） isadopted to numerically simulate HF and associated MS. Several post-processing tools, includingfrequency-magnitude distribution （b-value）, fractal dimension （D-value）, and seismic events clustering,are utilized to interpret numerical results. A non-parametric clustering algorithm designed specificallyfor FDEM is used to reduce the mesh dependency and extract more realistic seismic information.Simulation results indicated that at the local scale, the HF process tends to propagate following the rockmass discontinuities; while at the reservoir scale, it tends to develop in the direction parallel to themaximum in-situ stress. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
