Shock wave caused by a sudden release of high-energy,such as explosion and blast,usually affects a significant range of areas.The utilization of a uniform fine mesh to capture sharp shock wave and to obtain precise re...Shock wave caused by a sudden release of high-energy,such as explosion and blast,usually affects a significant range of areas.The utilization of a uniform fine mesh to capture sharp shock wave and to obtain precise results is inefficient in terms of computational resource.This is particularly evident when large-scale fluid field simulations are conducted with significant differences in computational domain size.In this work,a variable-domain-size adaptive mesh enlargement(vAME)method is developed based on the proposed adaptive mesh enlargement(AME)method for modeling multi-explosives explosion problems.The vAME method reduces the division of numerous empty areas or unnecessary computational domains by adaptively suspending enlargement operation in one or two directions,rather than in all directions as in AME method.A series of numerical tests via AME and vAME with varying nonintegral enlargement ratios and different mesh numbers are simulated to verify the efficiency and order of accuracy.An estimate of speedup ratio is analyzed for further efficiency comparison.Several large-scale near-ground explosion experiments with single/multiple explosives are performed to analyze the shock wave superposition formed by the incident wave,reflected wave,and Mach wave.Additionally,the vAME method is employed to validate the accuracy,as well as to investigate the performance of the fluid field and shock wave propagation,considering explosive quantities ranging from 1 to 5 while maintaining a constant total mass.The results show a satisfactory correlation between the overpressure versus time curves for experiments and numerical simulations.The vAME method yields a competitive efficiency,increasing the computational speed to 3.0 and approximately 120,000 times in comparison to AME and the fully fine mesh method,respectively.It indicates that the vAME method reduces the computational cost with minimal impact on the results for such large-scale high-energy release problems with significant differences in computational domain size.展开更多
The global rapid transition towards sustainable energy systems has heightened the demand for highperformance lithium metal batteries(LMBs),where understanding interfacial phenomena is paramount.In this contribution,we...The global rapid transition towards sustainable energy systems has heightened the demand for highperformance lithium metal batteries(LMBs),where understanding interfacial phenomena is paramount.In this contribution,we present an on-the-fly machine learning molecular dynamics(OTF-MLMD)approach to probe the complex side reactions at lithium metal anode–electrolyte interfaces with exceptional accuracy and computational efficiency.The machine learning force field(MLFF)was firstly validated in a bulk-phase system comprising twenty 1,2-dimethoxyethane(DME)molecules,demonstrating energy fluctuations and structural parameters in close agreement with ab initio molecular dynamics(AIMD)benchmarks.Subsequent simulations of lithium–DME and lithium–electrolyte interfaces revealed minimal discrepancies in energy,bond lengths,and net charge variations(notably in FSI-species),underscoring the method's DFT-level precision of the approach.A further small-scale interfacial model enabled on-the-fly training over a mere of 340 fs,which was then successfully transferred to a large-scale simulation encompassing nearly 300,000 atoms,representing the largest interfacial model in LMB research up to date.The hierarchical validation strategy not only establishes the robustness of the MLFF in capturing both interfacial and bulk-phase chemistry but also paves the way for statistically meaningful simulations of battery interfaces.The fruitful findings highlight the transformative potential of OTF-MLMD in bridging the gap between atomistic accuracy and macroscopic modeling,affording a universal approach to understand interfacial reactions in LMBs.展开更多
As groundwater table declination is an important factor resulting in degradation of eco-environment in the Minqin Basin, China, it is significant to investigate and understand the groundwater table dynamics in this ar...As groundwater table declination is an important factor resulting in degradation of eco-environment in the Minqin Basin, China, it is significant to investigate and understand the groundwater table dynamics in this area. According to the physical and geographical conditions of the Minqin Basin, a hydrogeological conceptual model and a mathematical model were established, and the mathematical model was figured out by using Finite Element subsurface Flow system （Feflow）. Accurate hydrogeological parameters were acquired, and the spatio-temporal distribution dynamics of groundwater table for 1983-2001 were also simulated. The model performed well with a correlation coefficient of 0.977 and a mean error of 0.9768 m. The inflow and outflow of the groundwater system were predicted by time series analysis, and the groundwater table dynamics for 2011 were further acquired. Gen- erally the groundwater table in the Minqin Basin would continue to decline. The groundwater table would decline during spring and summer irrigation, while it would rise during autumn-winter irrigation. The groundwater depression cones would expand with the increase of center depths. Therefore, regulatory measures should be taken to prevent the declination of groundwater table and improve the eco-environment of this area.展开更多
A solution scheme is proposed in this paper for an existing RTDHT system to simulate large-scale finite element （FE） numerical substructures. The analysis of the FE numerical substructure is split into response anal...A solution scheme is proposed in this paper for an existing RTDHT system to simulate large-scale finite element （FE） numerical substructures. The analysis of the FE numerical substructure is split into response analysis and signal generation tasks, and executed in two different target computers in real-time. One target computer implements the response analysis task, wherein a large time-step is used to solve the FE substructure, and another target computer implements the signal generation task, wherein an interpolation program is used to generate control signals in a small time-step to meet the input demand of the controller. By using this strategy, the scale of the FE numerical substructure simulation may be increased significantly. The proposed scheme is initially verified by two FE numerical substructure models with 98 and 1240 degrees of freedom （DOFs）. Thereafter, RTDHTs of a single frame-foundation structure are implemented where the foundation, considered as the numerical substructure, is simulated by the FE model with 1240 DOFs. Good agreements between the results of the RTDHT and those from the FE analysis in ABAQUS are obtained.展开更多
The analytical solution of the convection diffusion equation is considered by two-dimensional Fourier transform and the inverse Fourier transform. To get the numerical solution, the Crank-Nicolson finite difference me...The analytical solution of the convection diffusion equation is considered by two-dimensional Fourier transform and the inverse Fourier transform. To get the numerical solution, the Crank-Nicolson finite difference method is constructed, which is second-order accurate in time and space. Numerical simulation shows excellent agreement with the analytical solution. The dynamic visualization of the simulating results is realized on ArcGIS platform. This work provides a quick and intuitive decision-making basis for water resources protection, especially in dealing with water pollution emergencies.展开更多
Based on MATLAB, a new model-BRF network model is founded to be used in groundwater dynamic simulation and prediction. It is systematically studied about the training sample set, testing sample set, the pretreatment o...Based on MATLAB, a new model-BRF network model is founded to be used in groundwater dynamic simulation and prediction. It is systematically studied about the training sample set, testing sample set, the pretreatment of the original data, neural network construction, training, testing and evaluating the entire process. A favorable result is achieved by applying the model to simulate and predict groundwater dynamics, which shows this new method is precise and scientific.展开更多
We analyze a large-scale molecular dynamics simulation of work hardening in a model system of a ductile solid. With tensile loading, we observe emission of thousands of dislocations from two sharp cracks. The dislocat...We analyze a large-scale molecular dynamics simulation of work hardening in a model system of a ductile solid. With tensile loading, we observe emission of thousands of dislocations from two sharp cracks. The dislocations interact in a complex way, revealing three fundamental mechanisms of work-hardening in this ductile material. These are (1) dislocation cutting processes, jog formation and generation of trails of point defects; (2) activation of secondary slip systems by Frank-Read and cross-slip mechanisms; and (3) formation of sessile dislocations such as Lomer-Cottrell locks. We report the discovery of a new class of point defects referred to as trail of partial point defects, which could play an important role in situations when partial dislocations dominate plasticity. Another important result of the present work is the rediscovery of the Fleischer-mechanism of cross-slip of partial dislocations that was theoretically proposed more than 50 years ago, and is now, for the first time, confirmed by atomistic simulation. On the typical time scale of molecular dynamics simulations, the dislocations self-organize into a complex sessile defect topology. Our analysis illustrates numerous mechanisms formerly only conjectured in textbooks and observed indirectly in experiments. It is the first time that such a rich set of fundamental phenomena have been revealed in a single computer simulation, and its dynamical evolution has been studied. The present study exemplifies the simulation and analysis of the complex nonlinear dynamics of a many-particle system during failure using ultra-large scale computing.展开更多
As the rapid growth of population and social economy, the situation of water resources shortage in Beijing city becomes more and more serious. Karst groundwater in Beijing has great potential for development. The reas...As the rapid growth of population and social economy, the situation of water resources shortage in Beijing city becomes more and more serious. Karst groundwater in Beijing has great potential for development. The reasonable exploitation of karst groundwater can enhance the water-supply stability of Beijing city. Firstly, the distribution of springs has been investigated in Fangshan, Beijing, and the characteristics of these springs have also been analyzed. Secondly, the hydrogeological conceptual model has been built, based on this, the groundwater flow numerical simulation model was established, and the parameter identification and validation of the model were performed under groundwater level and spring discharge. The results shows that the simulated values of groundwater level and spring discharge are very close to measured values, and the model can be used for groundwater resources evaluation and spring discharge prediction. Finally, a reasonable exploitation design has been developed with three exploitation scenarios considering the spring discharge protection; meanwhile, the quantity of groundwater resources was evaluated in the karst aquifer. The simulation results indicate that different exploitation yields have a significant impact on spring discharge; and the effective measures should be taken to protect the spring discharge.展开更多
At Kuwana illegal dumping site in Japan, where hazardous waste was illegally dumped, groundwater was severely contaminated by Volatile Organic Compounds (VOCs). Groundwater was already remedied by conducting Pump-and-...At Kuwana illegal dumping site in Japan, where hazardous waste was illegally dumped, groundwater was severely contaminated by Volatile Organic Compounds (VOCs). Groundwater was already remedied by conducting Pump-and-Treat (P&T) after containment of all the waste by vertical slurry walls from 2002 to 2007. However, 1,4-dioxane was detected in both waste and groundwater outside of slurry walls after it was newly added into Japan environmental standards in late 2009, which suggested that the walls did not contain 1,4-dioxane completely. Our previous study developed a model to predict the 1,4-dioxane distribution in groundwater after the previous remediation at the site. In this study, numerical simulation was applied for remediation planning at the site based on the concept of Verified Follow Up (VF-UP) that had been proposed as a new approach to complete remediation effectively with consideration of future risks. The amount of waste to be removed and pumping plans were discussed by numerical simulation to achieve the remedial objective in which 1,4-dioxane in groundwater outside of walls is remedied within 10 years and 1,4-dioxane spreading throughout the walls is prevented in the case where a portion of waste is remained. Firstly, the amount of waste to be removed considering pumping plans for P&T was determined by scenario analysis. As a result, at least two-third of waste should be removed by combining with P&T. However, if the waste is remained, future risks of 1,4-dioxane spreading through the slurry walls may occur. Our simulation suggested that groundwater within the remaining waste must be pumped up at least 20 m3/d for containment of 1,4-dioxane within the remaining waste. In conclusion, our numerical simulation determined the amount of waste to be removed and the pumping plans for P&T to achieve the remedial objective effectively considering future risks based on the concept of VF-UP.展开更多
The desire to increase spatial and temporal resolution in modeling groundwater system has led to the requirement for intensive computational ability and large memory space. In the course of satisfying such requirement...The desire to increase spatial and temporal resolution in modeling groundwater system has led to the requirement for intensive computational ability and large memory space. In the course of satisfying such requirement, parallel computing has played a core role over the past several decades. This paper reviews the parallel algebraic linear solution methods and the parallel implementation technologies for groundwater simulation. This work is carried out to provide guidance to enable modelers of groundwater systems to make sensible choices when developing solution methods based upon the current state of knowledge in parallel computing.展开更多
The changes of development and utilization of karst groundwater in Sangu Spring Basin have made the original groundwater resource evaluation unable to meet the needs of future economic development.Based on analysis of...The changes of development and utilization of karst groundwater in Sangu Spring Basin have made the original groundwater resource evaluation unable to meet the needs of future economic development.Based on analysis of existing data,combined with the characteristics of supplement,runoff and draining of regional karst groundwater,the Visual Modelflow software was used to build a numerical simulation model of Sangu spring Basin.The amount of karst groundwater resource and groundwater environment of the Basin were evaluated under different exploitation schemes,and the changes of karst groundwater environment in the future ten years were also predicted.The fitting error which is less than 0.5 m between the calculated value and measured value of the water level in the fitted borehole accounts for 93%.For the lithologically and structurally complex Sangu Spring Basin,the fitting effect of numerical simulation model was ideal.On the basis of the current mining amount of 111.80 million m3/a,the total redistributed exploited amount in the spring region was 61.79 million m3/a.Under the condition that the quantity of recoverable resources reached 173.59 million m3/a and under different precipitation schemes,all constraint conditions were satisfied,such as regional water level drawdown,maximum allowable water level drawdown in every simulated water source area and the flow rate of Guobi Spring.The results will provide a scientific basis for the rational development and utilization of karst groundwater in Sangu Spring Basin.展开更多
With the purpose of making calculation more efficient in practical hydraulic simulations, an improved algorithm was proposed and was applied in the practical water distribution field. This methodology was developed by...With the purpose of making calculation more efficient in practical hydraulic simulations, an improved algorithm was proposed and was applied in the practical water distribution field. This methodology was developed by expanding the traditional loop-equation theory through utilization of the advantages of the graph theory in efficiency. The utilization of the spanning tree technique from graph theory makes the proposed algorithm efficient in calculation and simple to use for computer coding. The algorithms for topological generation and practical implementations are presented in detail in this paper. Through the application to a practical urban system, the consumption of the CPU time and computation memory were decreased while the accuracy was greatly enhanced compared with the present existing methods.展开更多
Groundwater is a vital component of the hydrological cycle and essential for the sustainable development of ecosystems.Numerical simulation methods are key tools for addressing scientific challenges in groundwater res...Groundwater is a vital component of the hydrological cycle and essential for the sustainable development of ecosystems.Numerical simulation methods are key tools for addressing scientific challenges in groundwater research.This study uses bibliometric visualization analysis to examine the progress and trends in groundwater numerical simulation methods.By analyzing literature indexed in the Web of Science database from January 1990 to February 2023,and employing tools such as Citespace and VOSviewer,we assessed publication volume,research institutions and their collaborations,prolific scholars,keyword clustering,and emerging trends.The findings indicate an overall upward trend in both the number of publications and citations concerning groundwater numerical simulations.Since 2010,the number of publications has tripled compared to the total before 2010,underscoring the increasing significance and potential of numerical simulation methods in groundwater science.China,in particular,has shown remarkable growth in this field over the past decade,surpassing the United States,Canada,and Germany.This progress is closely linked to strong national support and active participation from research institutions,especially the contributions from teams at Hohai University,China University of Geosciences,and the University of Science and Technology of China.Collaboration between research teams is primarily seen between China and the United States,with less noticeable cooperation among other countries,resulting in a diverse and dispersed development pattern.Keyword analysis highlights that international research hotspots include groundwater recharge,karst water,geothermal water migration,seawater intrusion,variable density flow,contaminant and solute transport,pollution remediation,and land subsidence.Looking ahead,groundwater numerical simulations are expected to play a more prominent role in areas such as climate change,surface water-groundwater interactions,the impact of groundwater nitrates on the environment and health,submarine groundwater discharge,ecological water use,groundwater management,and risk prevention.展开更多
BTEX contaminants in groundwater seriously impact the ecological environment and human health that has become one of the urgent problems needed to be solved.Due to its low density,low solubility and strong volatility,...BTEX contaminants in groundwater seriously impact the ecological environment and human health that has become one of the urgent problems needed to be solved.Due to its low density,low solubility and strong volatility,BTEX in groundwater usually form non-aqueous phase liquid(NAPL) contaminants and exist in three phases:gas,aqueous and oil phase.Air sparging(AS) is an in situ treatment technology展开更多
Based on random theory, fluid dynamics , porous media and soil mechanics, the porosity and random characteristic of the two-layer soft soil in Wuhan region were studied in this paper. The random seepage coefficient on...Based on random theory, fluid dynamics , porous media and soil mechanics, the porosity and random characteristic of the two-layer soft soil in Wuhan region were studied in this paper. The random seepage coefficient on the two-layer soft soil was analyzed, and the seepage model and its random distribution Junction mere given. The groundwater flow differential equations related to the two layer soft soil structure were also established. The evaluation procedure of effect boundary on the pumping water in deep foundation pit was put forward. Moreover , with an engineering example, the probability distribution on random boundary prediction for pumping water of foundation pit was computed.展开更多
Through the study of mutual process between groundwater systems and eco-environmental water demand, the eco-environmental water demand is brought into groundwater systems model as the important water consumption item ...Through the study of mutual process between groundwater systems and eco-environmental water demand, the eco-environmental water demand is brought into groundwater systems model as the important water consumption item and unification of groundwater抯 economic, environmental and ecological functions were taken into account. Based on eco-environmental water demand at Da抋n in Jilin province, a three-dimensional simulation and optimized management model of groundwater systems was established. All water balance components of groundwater systems in 1998 and 1999 were simulated with this model and the best optimal exploitation scheme of groundwater systems in 2000 was determined, so that groundwater resource was efficiently utilized and good economic, ecologic and social benefits were obtained.展开更多
Simulation of flow in fractured aquifers is a complex issue. The problem of mathematical modeling of highly heterogeneous porous media, typical of natural systems, couples with the needs making proper simplifying assu...Simulation of flow in fractured aquifers is a complex issue. The problem of mathematical modeling of highly heterogeneous porous media, typical of natural systems, couples with the needs making proper simplifying assumptions and approximations. In this kind of groundwater systems, studying contamination spreading and analyzing risk are challenging tasks. The main difficulty stems from determining both the travel times and the maximum distances covered by pollutants. In this context, the risk of contamination in the deep carbonate aquifer of the Augusta coastal area is presented. We used a geostatistical approach and numerical codes (MODFLOW-2000, MT3DMS) to reconstruct the complex geological framework of the study area where several contamination scenarios of hypothetical point source in a risk assessment framework were simulated. Results on the contaminant spreading are discussed and the effect of the geological structures characterizing the zone under study, namely horst and graben, are described.展开更多
In order to simulate the recovery of groundwater funnels under the condition of reducing groundwater abstraction, hydrogeological conditions of recoverability construction of Shijiazhuang groundwater funnel were analy...In order to simulate the recovery of groundwater funnels under the condition of reducing groundwater abstraction, hydrogeological conditions of recoverability construction of Shijiazhuang groundwater funnel were analyzed, and a numerical simulation method was used based on the change of various parameters. The results show that the groundwater flow model can accurately reflect groundwater hydrogeological characteristics, and can guarantee the reliability of groundwater restoration prediction. The research has set up four schemes for rural water-saving, planting structure adjustment, urban reducing abstraction and integrated method. The effect of four restoration schemes on the restoration of groundwater funnels was compared with water table variations of two observation well. Comparison results show that the level changes of plan Three and Four are different from the other two kinds of exploitation and the drop trend of water table in the funnel area is flat. So we can conclude that Plan Three and Four have significant effect on the groundwater funnel restoration of Shijiazhuang.展开更多
The dynamics of secondary large-scale structures in electron-temperature-gradient （ETG） turbulence is investigated based on gyrofluid simulations in sheared slab geometry. It is found that structural bifurcation to ...The dynamics of secondary large-scale structures in electron-temperature-gradient （ETG） turbulence is investigated based on gyrofluid simulations in sheared slab geometry. It is found that structural bifurcation to zonal flow dominated or streamer-like states depends on the spectral anisotropy of turbulent ETG fluctuation, which is governed by the magnetic shear. The turbulent electron transport is suppressed by enhanced zonal flows. However, it is still low even if the streamer is formed in ETG turbulence with strong shears. It is shown that the low transport may be related to the secondary excitation of poloidal long-wavelength mode due to the beat wave of the most unstable components or a modulation instability. This large-scale structure with a low frequency and a long wavelength may saturate, or at least contribute to the saturation of ETG fluctuations through a poloidal mode coupling. The result suggests a low fluctuation level in ETG turbulence.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12302435 and 12221002)。
文摘Shock wave caused by a sudden release of high-energy,such as explosion and blast,usually affects a significant range of areas.The utilization of a uniform fine mesh to capture sharp shock wave and to obtain precise results is inefficient in terms of computational resource.This is particularly evident when large-scale fluid field simulations are conducted with significant differences in computational domain size.In this work,a variable-domain-size adaptive mesh enlargement(vAME)method is developed based on the proposed adaptive mesh enlargement(AME)method for modeling multi-explosives explosion problems.The vAME method reduces the division of numerous empty areas or unnecessary computational domains by adaptively suspending enlargement operation in one or two directions,rather than in all directions as in AME method.A series of numerical tests via AME and vAME with varying nonintegral enlargement ratios and different mesh numbers are simulated to verify the efficiency and order of accuracy.An estimate of speedup ratio is analyzed for further efficiency comparison.Several large-scale near-ground explosion experiments with single/multiple explosives are performed to analyze the shock wave superposition formed by the incident wave,reflected wave,and Mach wave.Additionally,the vAME method is employed to validate the accuracy,as well as to investigate the performance of the fluid field and shock wave propagation,considering explosive quantities ranging from 1 to 5 while maintaining a constant total mass.The results show a satisfactory correlation between the overpressure versus time curves for experiments and numerical simulations.The vAME method yields a competitive efficiency,increasing the computational speed to 3.0 and approximately 120,000 times in comparison to AME and the fully fine mesh method,respectively.It indicates that the vAME method reduces the computational cost with minimal impact on the results for such large-scale high-energy release problems with significant differences in computational domain size.
基金supported by the National Key Research and Development Program(2021YFB2500300)the National Natural Science Foundation of China(T2322015,92472101,22393903,22393900,and 52394170)+1 种基金the Beijing Municipal Natural Science Foundation(L247015 and L233004)Tsinghua University Initiative Scientific Research Program。
文摘The global rapid transition towards sustainable energy systems has heightened the demand for highperformance lithium metal batteries(LMBs),where understanding interfacial phenomena is paramount.In this contribution,we present an on-the-fly machine learning molecular dynamics(OTF-MLMD)approach to probe the complex side reactions at lithium metal anode–electrolyte interfaces with exceptional accuracy and computational efficiency.The machine learning force field(MLFF)was firstly validated in a bulk-phase system comprising twenty 1,2-dimethoxyethane(DME)molecules,demonstrating energy fluctuations and structural parameters in close agreement with ab initio molecular dynamics(AIMD)benchmarks.Subsequent simulations of lithium–DME and lithium–electrolyte interfaces revealed minimal discrepancies in energy,bond lengths,and net charge variations(notably in FSI-species),underscoring the method's DFT-level precision of the approach.A further small-scale interfacial model enabled on-the-fly training over a mere of 340 fs,which was then successfully transferred to a large-scale simulation encompassing nearly 300,000 atoms,representing the largest interfacial model in LMB research up to date.The hierarchical validation strategy not only establishes the robustness of the MLFF in capturing both interfacial and bulk-phase chemistry but also paves the way for statistically meaningful simulations of battery interfaces.The fruitful findings highlight the transformative potential of OTF-MLMD in bridging the gap between atomistic accuracy and macroscopic modeling,affording a universal approach to understand interfacial reactions in LMBs.
基金funded by the National Natural Science Foundation of China(50879071 and 40801103)the Ph.D.Programs Foundation of the Ministry of Education of China (200800271029)
文摘As groundwater table declination is an important factor resulting in degradation of eco-environment in the Minqin Basin, China, it is significant to investigate and understand the groundwater table dynamics in this area. According to the physical and geographical conditions of the Minqin Basin, a hydrogeological conceptual model and a mathematical model were established, and the mathematical model was figured out by using Finite Element subsurface Flow system （Feflow）. Accurate hydrogeological parameters were acquired, and the spatio-temporal distribution dynamics of groundwater table for 1983-2001 were also simulated. The model performed well with a correlation coefficient of 0.977 and a mean error of 0.9768 m. The inflow and outflow of the groundwater system were predicted by time series analysis, and the groundwater table dynamics for 2011 were further acquired. Gen- erally the groundwater table in the Minqin Basin would continue to decline. The groundwater table would decline during spring and summer irrigation, while it would rise during autumn-winter irrigation. The groundwater depression cones would expand with the increase of center depths. Therefore, regulatory measures should be taken to prevent the declination of groundwater table and improve the eco-environment of this area.
基金National Natural Science Foundation under Grant Nos.51179093,91215301 and 41274106the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No.20130002110032Tsinghua University Initiative Scientific Research Program under Grant No.20131089285
文摘A solution scheme is proposed in this paper for an existing RTDHT system to simulate large-scale finite element （FE） numerical substructures. The analysis of the FE numerical substructure is split into response analysis and signal generation tasks, and executed in two different target computers in real-time. One target computer implements the response analysis task, wherein a large time-step is used to solve the FE substructure, and another target computer implements the signal generation task, wherein an interpolation program is used to generate control signals in a small time-step to meet the input demand of the controller. By using this strategy, the scale of the FE numerical substructure simulation may be increased significantly. The proposed scheme is initially verified by two FE numerical substructure models with 98 and 1240 degrees of freedom （DOFs）. Thereafter, RTDHTs of a single frame-foundation structure are implemented where the foundation, considered as the numerical substructure, is simulated by the FE model with 1240 DOFs. Good agreements between the results of the RTDHT and those from the FE analysis in ABAQUS are obtained.
文摘The analytical solution of the convection diffusion equation is considered by two-dimensional Fourier transform and the inverse Fourier transform. To get the numerical solution, the Crank-Nicolson finite difference method is constructed, which is second-order accurate in time and space. Numerical simulation shows excellent agreement with the analytical solution. The dynamic visualization of the simulating results is realized on ArcGIS platform. This work provides a quick and intuitive decision-making basis for water resources protection, especially in dealing with water pollution emergencies.
文摘Based on MATLAB, a new model-BRF network model is founded to be used in groundwater dynamic simulation and prediction. It is systematically studied about the training sample set, testing sample set, the pretreatment of the original data, neural network construction, training, testing and evaluating the entire process. A favorable result is achieved by applying the model to simulate and predict groundwater dynamics, which shows this new method is precise and scientific.
文摘We analyze a large-scale molecular dynamics simulation of work hardening in a model system of a ductile solid. With tensile loading, we observe emission of thousands of dislocations from two sharp cracks. The dislocations interact in a complex way, revealing three fundamental mechanisms of work-hardening in this ductile material. These are (1) dislocation cutting processes, jog formation and generation of trails of point defects; (2) activation of secondary slip systems by Frank-Read and cross-slip mechanisms; and (3) formation of sessile dislocations such as Lomer-Cottrell locks. We report the discovery of a new class of point defects referred to as trail of partial point defects, which could play an important role in situations when partial dislocations dominate plasticity. Another important result of the present work is the rediscovery of the Fleischer-mechanism of cross-slip of partial dislocations that was theoretically proposed more than 50 years ago, and is now, for the first time, confirmed by atomistic simulation. On the typical time scale of molecular dynamics simulations, the dislocations self-organize into a complex sessile defect topology. Our analysis illustrates numerous mechanisms formerly only conjectured in textbooks and observed indirectly in experiments. It is the first time that such a rich set of fundamental phenomena have been revealed in a single computer simulation, and its dynamical evolution has been studied. The present study exemplifies the simulation and analysis of the complex nonlinear dynamics of a many-particle system during failure using ultra-large scale computing.
基金generously supported by National Natural Science Foundation of China(Grant No.51459003)the Project of Karst Groundwater Resources Exploration and Assessment in Beijing(BJYRS-ZT-01)
文摘As the rapid growth of population and social economy, the situation of water resources shortage in Beijing city becomes more and more serious. Karst groundwater in Beijing has great potential for development. The reasonable exploitation of karst groundwater can enhance the water-supply stability of Beijing city. Firstly, the distribution of springs has been investigated in Fangshan, Beijing, and the characteristics of these springs have also been analyzed. Secondly, the hydrogeological conceptual model has been built, based on this, the groundwater flow numerical simulation model was established, and the parameter identification and validation of the model were performed under groundwater level and spring discharge. The results shows that the simulated values of groundwater level and spring discharge are very close to measured values, and the model can be used for groundwater resources evaluation and spring discharge prediction. Finally, a reasonable exploitation design has been developed with three exploitation scenarios considering the spring discharge protection; meanwhile, the quantity of groundwater resources was evaluated in the karst aquifer. The simulation results indicate that different exploitation yields have a significant impact on spring discharge; and the effective measures should be taken to protect the spring discharge.
文摘At Kuwana illegal dumping site in Japan, where hazardous waste was illegally dumped, groundwater was severely contaminated by Volatile Organic Compounds (VOCs). Groundwater was already remedied by conducting Pump-and-Treat (P&T) after containment of all the waste by vertical slurry walls from 2002 to 2007. However, 1,4-dioxane was detected in both waste and groundwater outside of slurry walls after it was newly added into Japan environmental standards in late 2009, which suggested that the walls did not contain 1,4-dioxane completely. Our previous study developed a model to predict the 1,4-dioxane distribution in groundwater after the previous remediation at the site. In this study, numerical simulation was applied for remediation planning at the site based on the concept of Verified Follow Up (VF-UP) that had been proposed as a new approach to complete remediation effectively with consideration of future risks. The amount of waste to be removed and pumping plans were discussed by numerical simulation to achieve the remedial objective in which 1,4-dioxane in groundwater outside of walls is remedied within 10 years and 1,4-dioxane spreading throughout the walls is prevented in the case where a portion of waste is remained. Firstly, the amount of waste to be removed considering pumping plans for P&T was determined by scenario analysis. As a result, at least two-third of waste should be removed by combining with P&T. However, if the waste is remained, future risks of 1,4-dioxane spreading through the slurry walls may occur. Our simulation suggested that groundwater within the remaining waste must be pumped up at least 20 m3/d for containment of 1,4-dioxane within the remaining waste. In conclusion, our numerical simulation determined the amount of waste to be removed and the pumping plans for P&T to achieve the remedial objective effectively considering future risks based on the concept of VF-UP.
基金supported by the National Basic Research Program (973 Program) of China under Grant No.2010CB428804 and 2011CB 309702
文摘The desire to increase spatial and temporal resolution in modeling groundwater system has led to the requirement for intensive computational ability and large memory space. In the course of satisfying such requirement, parallel computing has played a core role over the past several decades. This paper reviews the parallel algebraic linear solution methods and the parallel implementation technologies for groundwater simulation. This work is carried out to provide guidance to enable modelers of groundwater systems to make sensible choices when developing solution methods based upon the current state of knowledge in parallel computing.
基金This work was supported by the Fundamental Research Funds for the Chinese Academy of Geosciences(No.JYYWF20180401)the China Geological Survey project(No.DD20160296,DD20201123).
文摘The changes of development and utilization of karst groundwater in Sangu Spring Basin have made the original groundwater resource evaluation unable to meet the needs of future economic development.Based on analysis of existing data,combined with the characteristics of supplement,runoff and draining of regional karst groundwater,the Visual Modelflow software was used to build a numerical simulation model of Sangu spring Basin.The amount of karst groundwater resource and groundwater environment of the Basin were evaluated under different exploitation schemes,and the changes of karst groundwater environment in the future ten years were also predicted.The fitting error which is less than 0.5 m between the calculated value and measured value of the water level in the fitted borehole accounts for 93%.For the lithologically and structurally complex Sangu Spring Basin,the fitting effect of numerical simulation model was ideal.On the basis of the current mining amount of 111.80 million m3/a,the total redistributed exploited amount in the spring region was 61.79 million m3/a.Under the condition that the quantity of recoverable resources reached 173.59 million m3/a and under different precipitation schemes,all constraint conditions were satisfied,such as regional water level drawdown,maximum allowable water level drawdown in every simulated water source area and the flow rate of Guobi Spring.The results will provide a scientific basis for the rational development and utilization of karst groundwater in Sangu Spring Basin.
文摘With the purpose of making calculation more efficient in practical hydraulic simulations, an improved algorithm was proposed and was applied in the practical water distribution field. This methodology was developed by expanding the traditional loop-equation theory through utilization of the advantages of the graph theory in efficiency. The utilization of the spanning tree technique from graph theory makes the proposed algorithm efficient in calculation and simple to use for computer coding. The algorithms for topological generation and practical implementations are presented in detail in this paper. Through the application to a practical urban system, the consumption of the CPU time and computation memory were decreased while the accuracy was greatly enhanced compared with the present existing methods.
基金supported by the Institute of Hydrogeology and Environmental Geology,China Geological Survey"Coupling analysis of groundwater and land subsidence in typical cities of the North China Plain based on InSAR-GRACE technology"project under Grant No.KY202302the China Geological Survey"Research and promotion of digital water resources survey technology"project under Grant No.DD20230427the"Cloud platform geological survey node operation and maintenance and network security guarantee(Institute of Hydrogeology and Environmental Geology)"project under Grant No.DD20230719.
文摘Groundwater is a vital component of the hydrological cycle and essential for the sustainable development of ecosystems.Numerical simulation methods are key tools for addressing scientific challenges in groundwater research.This study uses bibliometric visualization analysis to examine the progress and trends in groundwater numerical simulation methods.By analyzing literature indexed in the Web of Science database from January 1990 to February 2023,and employing tools such as Citespace and VOSviewer,we assessed publication volume,research institutions and their collaborations,prolific scholars,keyword clustering,and emerging trends.The findings indicate an overall upward trend in both the number of publications and citations concerning groundwater numerical simulations.Since 2010,the number of publications has tripled compared to the total before 2010,underscoring the increasing significance and potential of numerical simulation methods in groundwater science.China,in particular,has shown remarkable growth in this field over the past decade,surpassing the United States,Canada,and Germany.This progress is closely linked to strong national support and active participation from research institutions,especially the contributions from teams at Hohai University,China University of Geosciences,and the University of Science and Technology of China.Collaboration between research teams is primarily seen between China and the United States,with less noticeable cooperation among other countries,resulting in a diverse and dispersed development pattern.Keyword analysis highlights that international research hotspots include groundwater recharge,karst water,geothermal water migration,seawater intrusion,variable density flow,contaminant and solute transport,pollution remediation,and land subsidence.Looking ahead,groundwater numerical simulations are expected to play a more prominent role in areas such as climate change,surface water-groundwater interactions,the impact of groundwater nitrates on the environment and health,submarine groundwater discharge,ecological water use,groundwater management,and risk prevention.
文摘BTEX contaminants in groundwater seriously impact the ecological environment and human health that has become one of the urgent problems needed to be solved.Due to its low density,low solubility and strong volatility,BTEX in groundwater usually form non-aqueous phase liquid(NAPL) contaminants and exist in three phases:gas,aqueous and oil phase.Air sparging(AS) is an in situ treatment technology
基金Supported by Financial Aid Project for Key Teachers of U-niversities
文摘Based on random theory, fluid dynamics , porous media and soil mechanics, the porosity and random characteristic of the two-layer soft soil in Wuhan region were studied in this paper. The random seepage coefficient on the two-layer soft soil was analyzed, and the seepage model and its random distribution Junction mere given. The groundwater flow differential equations related to the two layer soft soil structure were also established. The evaluation procedure of effect boundary on the pumping water in deep foundation pit was put forward. Moreover , with an engineering example, the probability distribution on random boundary prediction for pumping water of foundation pit was computed.
基金The Key Project of the National Ninth-Five-Year Plan No. 96-004-02-09The 48Project of Ministry of Water Resources No. 985106The Project of Chinese Academy of Sciences
文摘Through the study of mutual process between groundwater systems and eco-environmental water demand, the eco-environmental water demand is brought into groundwater systems model as the important water consumption item and unification of groundwater抯 economic, environmental and ecological functions were taken into account. Based on eco-environmental water demand at Da抋n in Jilin province, a three-dimensional simulation and optimized management model of groundwater systems was established. All water balance components of groundwater systems in 1998 and 1999 were simulated with this model and the best optimal exploitation scheme of groundwater systems in 2000 was determined, so that groundwater resource was efficiently utilized and good economic, ecologic and social benefits were obtained.
文摘Simulation of flow in fractured aquifers is a complex issue. The problem of mathematical modeling of highly heterogeneous porous media, typical of natural systems, couples with the needs making proper simplifying assumptions and approximations. In this kind of groundwater systems, studying contamination spreading and analyzing risk are challenging tasks. The main difficulty stems from determining both the travel times and the maximum distances covered by pollutants. In this context, the risk of contamination in the deep carbonate aquifer of the Augusta coastal area is presented. We used a geostatistical approach and numerical codes (MODFLOW-2000, MT3DMS) to reconstruct the complex geological framework of the study area where several contamination scenarios of hypothetical point source in a risk assessment framework were simulated. Results on the contaminant spreading are discussed and the effect of the geological structures characterizing the zone under study, namely horst and graben, are described.
基金supported by Public Welfare Project of Ministry of Water Resources(201501008)Natural Science Foundation of Hebei Province(D2015504019)
文摘In order to simulate the recovery of groundwater funnels under the condition of reducing groundwater abstraction, hydrogeological conditions of recoverability construction of Shijiazhuang groundwater funnel were analyzed, and a numerical simulation method was used based on the change of various parameters. The results show that the groundwater flow model can accurately reflect groundwater hydrogeological characteristics, and can guarantee the reliability of groundwater restoration prediction. The research has set up four schemes for rural water-saving, planting structure adjustment, urban reducing abstraction and integrated method. The effect of four restoration schemes on the restoration of groundwater funnels was compared with water table variations of two observation well. Comparison results show that the level changes of plan Three and Four are different from the other two kinds of exploitation and the drop trend of water table in the funnel area is flat. So we can conclude that Plan Three and Four have significant effect on the groundwater funnel restoration of Shijiazhuang.
基金supported in part by the National Natural Science Foundation of China(Nos.10135020 and 10575032)
文摘The dynamics of secondary large-scale structures in electron-temperature-gradient （ETG） turbulence is investigated based on gyrofluid simulations in sheared slab geometry. It is found that structural bifurcation to zonal flow dominated or streamer-like states depends on the spectral anisotropy of turbulent ETG fluctuation, which is governed by the magnetic shear. The turbulent electron transport is suppressed by enhanced zonal flows. However, it is still low even if the streamer is formed in ETG turbulence with strong shears. It is shown that the low transport may be related to the secondary excitation of poloidal long-wavelength mode due to the beat wave of the most unstable components or a modulation instability. This large-scale structure with a low frequency and a long wavelength may saturate, or at least contribute to the saturation of ETG fluctuations through a poloidal mode coupling. The result suggests a low fluctuation level in ETG turbulence.
