Porous materials present significant advantages for absorbing radioactive isotopes in nuclear waste streams.To improve absorption efficiency in nuclear waste treatment,a thorough understanding of the diffusion-advecti...Porous materials present significant advantages for absorbing radioactive isotopes in nuclear waste streams.To improve absorption efficiency in nuclear waste treatment,a thorough understanding of the diffusion-advection process within porous structures is essential for material design.In this study,we present advancements in the volumetric lattice Boltzmann method(VLBM)for modeling and simulating pore-scale diffusion-advection of radioactive isotopes within geopolymer porous structures.These structures are created using the phase field method(PFM)to precisely control pore architectures.In our VLBM approach,we introduce a concentration field of an isotope seamlessly coupled with the velocity field and solve it by the time evolution of its particle population function.To address the computational intensity inherent in the coupled lattice Boltzmann equations for velocity and concentration fields,we implement graphics processing unit(GPU)parallelization.Validation of the developed model involves examining the flow and diffusion fields in porous structures.Remarkably,good agreement is observed for both the velocity field from VLBM and multiphysics object-oriented simulation environment(MOOSE),and the concentration field from VLBM and the finite difference method(FDM).Furthermore,we investigate the effects of background flow,species diffusivity,and porosity on the diffusion-advection behavior by varying the background flow velocity,diffusion coefficient,and pore volume fraction,respectively.Notably,all three parameters exert an influence on the diffusion-advection process.Increased background flow and diffusivity markedly accelerate the process due to increased advection intensity and enhanced diffusion capability,respectively.Conversely,increasing the porosity has a less significant effect,causing a slight slowdown of the diffusion-advection process due to the expanded pore volume.This comprehensive parametric study provides valuable insights into the kinetics of isotope uptake in porous structures,facilitating the development of porous materials for nuclear waste treatment applications.展开更多
Natural gas hydrate(NGH),considered as a type of premium energy alternative to conventional hydrocarbons,has been broadly studied.The estimate of the total NGH resources in the world has decreased by more than 90%sinc...Natural gas hydrate(NGH),considered as a type of premium energy alternative to conventional hydrocarbons,has been broadly studied.The estimate of the total NGH resources in the world has decreased by more than 90%since the first evaluation in 1973.Geographic and geophysical conditions of the South China Sea(SCS)are favorable for the formation of NGH,which has been proved by drilling results up to date.The recoverability of the NGH in the SCS has been confirmed by the production tests using both vertical and horizontal wells.Since 2001,35 estimates of NGH resources in the SCS have been made,with relatively stable results varying between 600 and 900×109 ton oil equivalent.In these estimations,the volumetric method was commonly adopted,but the geological conditions,the migration-accumulation mechanisms of NGH,and the practical recoverability were not considered.These estimates cannot be regarded as evaluated resources according to the international resource evaluation standards,but are at most about prospective gas content of NGH,thus inefficient for guiding explorations and developments.To solve these problems,this study divides the past NGH surveys in the SCS into seven stages,acquires key geological parameters of every stage based on previous studies and analogy with other areas,evaluates the NGH resources of these seven stages by using the volumetric method,then adopts a new trend-analysis method to simulate the downward trend of these estimates,and finally predicts the NGH resources in the SCS at 2025 and 2030.The downward trend is because of the continuous improvement of NGH understanding over time,which is consistent with the trend of global NGH estimates.At the present stage(from 2019 to 2021),the average technically recoverable resource(ATRR)is 7.0×10^(12)m^(3),and the estimates of 2025 and 2030 ATRR are 6.46×10^(12)m^(3) and 4.01×10^(12)m^(3)respectively,with a difference of less than 40%.Therefore,it can be inferred that the ATRR of NGH in the SCS is between 4.0 and 6.5×10^(12)m^(3),with an average of 5.25×10^(12)m^(3).展开更多
This standard specifies the method summary, reagents, apparatus, sampling, procedure, test results calculation and permissible tolerance of the determination of magnesium oxide by CyDTA volumetric method.
Formulation and numerical evaluation of a novel twice-interpolation finite element method （TFEM） is presented for solid mechanics problems. In this method, the trial function for Galerkin weak form is constructed th...Formulation and numerical evaluation of a novel twice-interpolation finite element method （TFEM） is presented for solid mechanics problems. In this method, the trial function for Galerkin weak form is constructed through two stages of consecutive interpolation. The primary interpolation follows exactly the same procedure of standard FEM and is further reproduced according to both nodal values and averaged nodal gradients obtained from primary interpolation. The trial functions thus constructed have continuous nodal gradients and contain higher order polynomial without increasing total freedoms. Several benchmark examples and a real dam problem are used to examine the TFEM in terms of accuracy and convergence. Compared with standard FEM, TFEM can achieve significantly better accuracy and higher convergence rate, and the continuous nodal stress can be obtained without any smoothing operation. It is also found that TFEM is insensitive to the quality of the elemental mesh. In addition, the present TFEM can treat the incompressible material without any modification.展开更多
Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration ...Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration fatigue probabilistic life prediction model(VFPLPM)and a prediction method are proposed in this paper.Firstly,as one-dimensional volumetric method(ODVM)only considers the principle calculation direction,a three-dimensional space vector volumetric method(TSVVM)is proposed to improve fatigue life prediction accuracy for actual threedimensional engineering structure.Secondly,based on the two volumetric methods(ODVM and TSVVM),the material C-P-S-N fatigue curve model(CFCM)and the maximum entropy quantile function model(MEQFM),VFPLPM is established to predict the vibration fatigue probabilistic life of blade.The VFPLPM is combined with maximum stress method(MSM),ODVM and TSVVM to estimate vibration fatigue probabilistic life of blade simulator by finite element simulation,and is verified by vibration fatigue test.The results show that all of the three methods can predict the vibration fatigue probabilistic life of blade simulator well.VFPLPM &TSVVM method has the highest computational accuracy for considering stress gradient effect not only in the principle calculation direction but also in other space vector directions.展开更多
The development of a general discrete element method for irregularly shaped particles is the core issue of the simulation of the dynamic behavior of granular materials.The general energy-conserving contact theory is u...The development of a general discrete element method for irregularly shaped particles is the core issue of the simulation of the dynamic behavior of granular materials.The general energy-conserving contact theory is used to establish a universal discrete element method suitable for particle contact of arbitrary shape.In this study,three dimentional(3D)modeling and scanning techniques are used to obtain a triangular mesh representation of the true particles containing typical concave particles.The contact volumebased energy-conserving model is used to realize the contact detection between irregularly shaped particles,and the contact force model is refined and modified to describe the contact under real conditions.The inelastic collision processes between the particles and boundaries are simulated to verify the robustness of the modified contact force model and its applicability to the multi-point contact mode.In addition,the packing process and the flow process of a large number of irregular particles are simulated with the modified discrete element method(DEM)to illustrate the applicability of the method of complex problems.展开更多
基金supported as part of the Center for Hierarchical Waste Form Materials,an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science,Basic Energy Sciences under Award No.DE-SC0016574.
文摘Porous materials present significant advantages for absorbing radioactive isotopes in nuclear waste streams.To improve absorption efficiency in nuclear waste treatment,a thorough understanding of the diffusion-advection process within porous structures is essential for material design.In this study,we present advancements in the volumetric lattice Boltzmann method(VLBM)for modeling and simulating pore-scale diffusion-advection of radioactive isotopes within geopolymer porous structures.These structures are created using the phase field method(PFM)to precisely control pore architectures.In our VLBM approach,we introduce a concentration field of an isotope seamlessly coupled with the velocity field and solve it by the time evolution of its particle population function.To address the computational intensity inherent in the coupled lattice Boltzmann equations for velocity and concentration fields,we implement graphics processing unit(GPU)parallelization.Validation of the developed model involves examining the flow and diffusion fields in porous structures.Remarkably,good agreement is observed for both the velocity field from VLBM and multiphysics object-oriented simulation environment(MOOSE),and the concentration field from VLBM and the finite difference method(FDM).Furthermore,we investigate the effects of background flow,species diffusivity,and porosity on the diffusion-advection behavior by varying the background flow velocity,diffusion coefficient,and pore volume fraction,respectively.Notably,all three parameters exert an influence on the diffusion-advection process.Increased background flow and diffusivity markedly accelerate the process due to increased advection intensity and enhanced diffusion capability,respectively.Conversely,increasing the porosity has a less significant effect,causing a slight slowdown of the diffusion-advection process due to the expanded pore volume.This comprehensive parametric study provides valuable insights into the kinetics of isotope uptake in porous structures,facilitating the development of porous materials for nuclear waste treatment applications.
基金financially supported by the CAS consultation project“South China Sea Oil and Gas Comprehensive Development Strategy”(2019-ZW11-Z-035)the National Basic Research Program of China(973 Program)(2006CB202300,2011CB201100)the National High-Tech R&D Program of China(863 Program)(2013AA092600)。
文摘Natural gas hydrate(NGH),considered as a type of premium energy alternative to conventional hydrocarbons,has been broadly studied.The estimate of the total NGH resources in the world has decreased by more than 90%since the first evaluation in 1973.Geographic and geophysical conditions of the South China Sea(SCS)are favorable for the formation of NGH,which has been proved by drilling results up to date.The recoverability of the NGH in the SCS has been confirmed by the production tests using both vertical and horizontal wells.Since 2001,35 estimates of NGH resources in the SCS have been made,with relatively stable results varying between 600 and 900×109 ton oil equivalent.In these estimations,the volumetric method was commonly adopted,but the geological conditions,the migration-accumulation mechanisms of NGH,and the practical recoverability were not considered.These estimates cannot be regarded as evaluated resources according to the international resource evaluation standards,but are at most about prospective gas content of NGH,thus inefficient for guiding explorations and developments.To solve these problems,this study divides the past NGH surveys in the SCS into seven stages,acquires key geological parameters of every stage based on previous studies and analogy with other areas,evaluates the NGH resources of these seven stages by using the volumetric method,then adopts a new trend-analysis method to simulate the downward trend of these estimates,and finally predicts the NGH resources in the SCS at 2025 and 2030.The downward trend is because of the continuous improvement of NGH understanding over time,which is consistent with the trend of global NGH estimates.At the present stage(from 2019 to 2021),the average technically recoverable resource(ATRR)is 7.0×10^(12)m^(3),and the estimates of 2025 and 2030 ATRR are 6.46×10^(12)m^(3) and 4.01×10^(12)m^(3)respectively,with a difference of less than 40%.Therefore,it can be inferred that the ATRR of NGH in the SCS is between 4.0 and 6.5×10^(12)m^(3),with an average of 5.25×10^(12)m^(3).
文摘This standard specifies the method summary, reagents, apparatus, sampling, procedure, test results calculation and permissible tolerance of the determination of magnesium oxide by CyDTA volumetric method.
基金supported by the National Natural Science Foundation of China(50474053,50475134 and 50675081)the 863 project (2007AA042142)
文摘Formulation and numerical evaluation of a novel twice-interpolation finite element method （TFEM） is presented for solid mechanics problems. In this method, the trial function for Galerkin weak form is constructed through two stages of consecutive interpolation. The primary interpolation follows exactly the same procedure of standard FEM and is further reproduced according to both nodal values and averaged nodal gradients obtained from primary interpolation. The trial functions thus constructed have continuous nodal gradients and contain higher order polynomial without increasing total freedoms. Several benchmark examples and a real dam problem are used to examine the TFEM in terms of accuracy and convergence. Compared with standard FEM, TFEM can achieve significantly better accuracy and higher convergence rate, and the continuous nodal stress can be obtained without any smoothing operation. It is also found that TFEM is insensitive to the quality of the elemental mesh. In addition, the present TFEM can treat the incompressible material without any modification.
基金supported by the Aviation Science Foundation of China(No.20150252003)
文摘Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration fatigue probabilistic life prediction model(VFPLPM)and a prediction method are proposed in this paper.Firstly,as one-dimensional volumetric method(ODVM)only considers the principle calculation direction,a three-dimensional space vector volumetric method(TSVVM)is proposed to improve fatigue life prediction accuracy for actual threedimensional engineering structure.Secondly,based on the two volumetric methods(ODVM and TSVVM),the material C-P-S-N fatigue curve model(CFCM)and the maximum entropy quantile function model(MEQFM),VFPLPM is established to predict the vibration fatigue probabilistic life of blade.The VFPLPM is combined with maximum stress method(MSM),ODVM and TSVVM to estimate vibration fatigue probabilistic life of blade simulator by finite element simulation,and is verified by vibration fatigue test.The results show that all of the three methods can predict the vibration fatigue probabilistic life of blade simulator well.VFPLPM &TSVVM method has the highest computational accuracy for considering stress gradient effect not only in the principle calculation direction but also in other space vector directions.
基金supported by the National Key Research and Development Program of China(2018YFA0605902)the National Natural Science Foundation of China(42176241 and 11872136).
文摘The development of a general discrete element method for irregularly shaped particles is the core issue of the simulation of the dynamic behavior of granular materials.The general energy-conserving contact theory is used to establish a universal discrete element method suitable for particle contact of arbitrary shape.In this study,three dimentional(3D)modeling and scanning techniques are used to obtain a triangular mesh representation of the true particles containing typical concave particles.The contact volumebased energy-conserving model is used to realize the contact detection between irregularly shaped particles,and the contact force model is refined and modified to describe the contact under real conditions.The inelastic collision processes between the particles and boundaries are simulated to verify the robustness of the modified contact force model and its applicability to the multi-point contact mode.In addition,the packing process and the flow process of a large number of irregular particles are simulated with the modified discrete element method(DEM)to illustrate the applicability of the method of complex problems.
