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
To address the limitations of existing coupling methods in aero-engine system simulation,which fail to adaptively adjust iterative parameters and coupling relationships,which can result in low efficiency and in⁃stabil...To address the limitations of existing coupling methods in aero-engine system simulation,which fail to adaptively adjust iterative parameters and coupling relationships,which can result in low efficiency and in⁃stability,this study introduces a‘Dynamic Event-Driven Co-Simulation’algorithm integrated with decision tree algorithms.This algorithm separates the overall coupling relationships and the main solver from the primary mod⁃el,utilizing a dynamic event monitoring module to adaptively adjust simulation strategies,including iteration pa⁃rameters,coupling relationships,and convergence criteria.This facilitates efficient adaptive simulations of dy⁃namic events while balancing solution accuracy and computational efficiency.The research focuses on a twinshaft turbofan engine,establishing six system-level models that encompass overall performance and various sub⁃systems based on three coupling methods,along with a multidisciplinary multi-fidelity simulation framework in⁃corporating a 3D CFD nozzle model.The study tests both model exchange and coupled simulation methods under a 14 s transient acceleration and deceleration scenario.In a 100%throttle condition,a high-fidelity nozzle model is used to analyze the sensitivity of different convergence criteria on computational efficiency and accuracy.Re⁃sults indicate that the accuracy and efficiency achieved with this method are comparable to those of PROOSIS soft⁃ware(18 s and 35 s,respectively),while being 71%more efficient than Simulink software(62 s and 120 s,re⁃spectively).Furthermore,appropriately relaxing the convergence criteria for the 0D model(from 10-6 to 10-4)while enhancing those for the 3D model(from 3000 steps to 6000 steps)can effectively balance computational accuracy and efficiency.展开更多
The assembly of a protein complex is very important for its biological function,which can be investigated by determining the order of assembly/disassembly of its protein subunits.Although static structures of many pro...The assembly of a protein complex is very important for its biological function,which can be investigated by determining the order of assembly/disassembly of its protein subunits.Although static structures of many protein com-plexes are available in the protein data bank,their assembly/disassembly orders of subunits are largely unknown.In addition to experimental techniques for studying subcomplexes in the assembly/disassembly of a protein complex,computational methods can be used to predict the assembly/disassembly order.Since sampling is a nontrivial issue in simulating the assembly/disassembly process,coarse-grained simulations are more efficient than atomic simulations are.In this work,we developed computational protocols for predicting the assembly/disassembly orders of protein complexes via coarse-grained simulations.The protocols were illustrated via two protein complexes,and the predicted assembly/disassembly orders were consistent with the available experimental data.展开更多
Porous materials are widely used in the field of protection because of their excellent energy absorption characteristics.In this work,a series of polyurethane microscopic models are established and the effect of poros...Porous materials are widely used in the field of protection because of their excellent energy absorption characteristics.In this work,a series of polyurethane microscopic models are established and the effect of porosity on the shock waves is studied with classical molecular dynamics simulations.Firstly,shock Hugoniot relations for different porosities are obtained,which compare well with the experimental data.The pores collapse and form local stress wave,which results in the complex multi-wave structure of the shock wave.The microstructure analysis shows that the local stress increases and the local velocity decreases gradually during the process of pore collapse to complete compaction.Finally,it leads to stress relaxation and velocity homogenization.The shock stress peaks can be fitted with two exponential functions,and the amplitude of attenuation coefficient decreases with the increase of density.Besides,the pore collapse under shock or non-shock are discussed by the entropy increase rate of the system.The energy is dissipated mainly through the multiple interactions of the waves under shock.The energy is dissipated mainly by the friction between atoms under non-shock.展开更多
Both theory and simulation have played important roles in defining and illuminating the key mechanisms involved in substorms.Basic theories of magnetic reconnection and of interchange and ballooning instabilities were...Both theory and simulation have played important roles in defining and illuminating the key mechanisms involved in substorms.Basic theories of magnetic reconnection and of interchange and ballooning instabilities were developed more than 50 years ago,and these plasma physical concepts have been central in discussions of substorm physics.A vast amount of research on reconnection,including both theoretical and computational studies,has helped provide a picture of how reconnection operates in the collisionless environment of the magnetosphere.Still,however,we do not fully understand how key microscale processes and large-scale dynamics work together to determine the location and rate of reconnection.While in the last twenty years,it has become clear that interchange processes are important for transporting plasma through the plasma sheet in the form of bursty bulk flows and substorm expansions,we still have not reached the point where simulations are able to realistically and defensibly represent all of the important aspects of the phenomenon.More than two decades ago it was suggested that the ballooning instability,the basic theory for which dates from the 1950s,may play an important role in substorms.Now the majority of experts agree that regions of the plasma sheet are often linearly unstable to ideal-MHD ballooning.However,it is also clear that kinetic effects introduce important modifications to the MHD stability criterion.It is still uncertain whether ballooning plays a leading role in substorms or has just a minor part.Among the different types of simulations that have been applied to the substorm problem,global MHD codes are unique in that,in a sense, they represent the entire global substorm phenomenon,including coupling to the solar wind and ionosphere, and the important mechanisms of reconnection,interchange,and ballooning.However,they have not yet progressed to the point where they can accurately represent the whole phenomenon,because grid-resolution problems limit the accuracy with which they can solve the equations of ideal MHD and the couphng to the ionosphere,and they cannot accurately represent small-scale processes that violate ideal MHD.展开更多
Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetime...Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.展开更多
A deep understanding of explosive sensitivities and their factors is important for safe and reliable applications.However,quantitative prediction of the sensitivities is difficult.Here,reactive molecular dynamics simu...A deep understanding of explosive sensitivities and their factors is important for safe and reliable applications.However,quantitative prediction of the sensitivities is difficult.Here,reactive molecular dynamics simulation models for high-speed piston impacts on explosive supercells were established.Simulations were also performed to investigate shock-induced reactions of various high-energy explosives.The fraction of reacted explosive molecules in an initial supercell changed linearly with the propagation distance of the shock-wave front.The corresponding slope could be used as a reaction rate for a specific shock-loading velocity.Reaction rates that varied with the shock-loading pressure exhibited two-stage linearities with different slopes.The two inflection points corresponded to the initial and accelerated reactions,which respectively correlated to the thresholds of shock-induced ignition and detonation.Therefore,the ignition and detonation critical pressures could be determined.The sensitivity could then be a quantitative prediction of the critical pressure.The accuracies of the quantitative shock sensitivity predictions were verified by comparing the impact and shock sensitivities of common explosives and the characteristics of anisotropic shock-induced reactions.Molecular dynamics simulations quantitatively predict and rank shock sensitivities by using only crystal structures of the explosives.Overall,this method will enable the design and safe use of explosives.展开更多
A theoretical method to calculate multidimensional Franck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectroscopy of the anion O-3. Geometry optimization and harmon...A theoretical method to calculate multidimensional Franck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectroscopy of the anion O-3. Geometry optimization and harmonic vibrational frequency calculations have been performed on the AX～U4（）1A1 state of O3 and AX～U4（）2B1 state of O-3. Franck-Condon analyses and spectral simulation were carried out on the first photoelectron band of O-3. The theoretical spectrum obtained by employing CCSD（T）/6-311+G（2d,p） values are in excellent agreement with the observed one. In addition, the equilibrium geometry parameters, re（OO）= 0.135?5±0.000?5 nm and θe（O-O-O） =114.5±0.5°, of the AX～U4（）2B1 state of O-3, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation.展开更多
Tube hydroforming process is a relative new process f or production of structural parts of low weight and high rigidity. The successfu lness of the process depends largely on the a proper selection of loading path w h...Tube hydroforming process is a relative new process f or production of structural parts of low weight and high rigidity. The successfu lness of the process depends largely on the a proper selection of loading path w hich is axial feeding distance as related to the applied internal pressure. Due to the complicated nature of plastic deformation, a optimum loading path which w ill guarantee good hydroformed parts free of winkle and fracture has often to be determined by finite element analysis. In order to save trials and errors, adap tive FEM simulation method has been developed. To effectively apply the adaptive simulation method, we have to know the applicability of the method. In this pap er, a classification of tube hydroforming (THF) processes based on sensitivity to loading parameters has been suggested. Characteristics of the classification have been analyzed in terms of failure mode, dominant loading parameters and th eir working windows. It was discussed that the so called pressure dominant THF p rocess is the most difficult process for both simulation in FEM analysis and pra ctical operation in real manufacturing situation. To effectively find out the op timum loading path for pressure dominant THF process, adaptive FEM simulation st rategies are mostly needed.展开更多
The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed(HCP)zirconium were investigated by molecular dynamics simulations,which were combined with experimental...The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed(HCP)zirconium were investigated by molecular dynamics simulations,which were combined with experimental observation under high resolution transmission electron microscopy.The results show that externally applied loading first induced the HCP to body-centered cubic(BCC)phase transition in the Pitsch-Schrader(PS)orientation relationship(OR).Then,the face-centered cubic(FCC)structure transformed from the BCC phase in the Bain path.However,the HCP-to-BCC transition was incomplete at 100 K and 300 K,resulting in a prismatic-type OR between the FCC and original HCP phase.Additionally,at the temperature ranging from 100 K to 600 K,the inverse BCC-to-HCP transition occurred locally following other variants of the PS OR,resulting in a basal-type relation between the newly generated HCP and FCC phases.A higher tensile temperature promoted the amount of FCC phase transforming into the BCC phase when the strain exceeded 45%.Besides,the crystal stretched at lower temperatures exhibits relatively higher strength but by the compromise of plasticity.This study reveals the deformation mechanisms in HCP-Zr at different temperatures,which may provide a better understanding of the deformation mechanism of zirconium alloys under different application environments.展开更多
Pressing process is a manufacturing method that obtained work piece with certain dimension, shape and capability through die forcing roughcast to produce plastic deformation or separate. This paper focuses on the key ...Pressing process is a manufacturing method that obtained work piece with certain dimension, shape and capability through die forcing roughcast to produce plastic deformation or separate. This paper focuses on the key problems of visualization simulation in pressing die. The final aim is that numerical simulation system can simulate the process of processing forming technique, which can supply some necessary and accurate key parameters for die design. The detail description of mechanical characteristic and key technique of sheet forming technique is discussed. Pressing forming method is one of the most important forming techniques of metal forming, which has special mechanical characteristics. The character of sheet pressing forming is that the deformation of thickness direction is very small in contrast to other directions. The deformation mode of sheet forming mainly has the following kinds: bi-directional stretch, plane stress, stretches, depths extend, bending and counter-bending. The essence of press forming is the transferring course that the transferring region of rough comes to deformation by outside force, which is main researching principle in forming and the transferring field. The analysis of pressing forming course, disclose the feature of stress-strain and their changing rule, then pressing process and forming parameters could be obtained. So the states of force and deformation of transferring region is key to determine character about the varieties of pressing transferring. The paper analyzes these factors, which may influence forming precision in pressing process. In traditional methods, some key parameter such as spring-back, bending radius for die design are calculated by experience formula or select from data table. The paper brings forward the calculation methods of key parameter in the case of drawing finite element method and numerical simulation into pressing die design. In order to calculate the value of key parameters based on data supplied by FEM, a numerical simulation application is finished combined with two descriptions of work piece deformation NURBS and discrete piece. The numerical simulation is programmed on Microsoft Visual C++ with OpenGL as the graphics tool. It establishes numerical simulation program, dynamically simulates the process of sheet pressing figuration, and gets good effects.展开更多
[Objective]This study aims to develop a thermodynamically consistent phase-field framework for modeling the initiation and evolution of discontinuous structures in geomaterials.[Methods]Our model introduces crack driv...[Objective]This study aims to develop a thermodynamically consistent phase-field framework for modeling the initiation and evolution of discontinuous structures in geomaterials.[Methods]Our model introduces crack driving forces derived from the volumetric-deviatoric strain decomposition strategy,incorporating distinct tension,compression,and shear degradation mechanisms.Inertia effects capture compaction-band formation driven by wave-like disturbances,grain crushing,and frictional rearrangement.A monolithic algorithm ensures numerical stability and rapid convergence.[Results]The framework reproduces tensile,shear,mixed tensile-shear,and compressive-shear failures using the Benzeggagh-Kenane criterion.Validation against benchmark simulations-including uniaxial compression of rock-like and triaxial compression of V-notched sandstone specimens-demonstrates accurate predictions of crack initiation stress,localization orientation,and energy dissipation.[Conclusions]The framework provides a unified and robust numerical tool for analyzing the spatiotemporal evolution of strain localization and fracture in geomaterials.[Significance]By linking microscale fracture dynamics with macroscale failure within a thermodynamically consistent scheme,this study advances predictive modeling of rock stability,slope failure,and subsurface energy systems,contributing to safer and more sustainable geotechnical practice.展开更多
In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-...In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-band.Two separate EIOs are coupled through a specific single-gap coupling field supported by a designed gap waveguide with length Lg,which form the phase-locked EIOs based on the commonly-resonated system.As a whole system,the system has been focused on with mode analysis based on different single-gap coupling fields,mode hopping,which present the variation of phase difference between the two-beam-wave interactions when changing Lg.To demonstrate the effectiveness of the proposed circuit system in producing the phase locking,we conducted particle-in-cell(PIC)simulations to show that the interesting mode hopping occurs with the phase difference of O and r between the output signals from two output ports,corresponding to the excitation of the TMn mode with different n.Simulation results show that 1)the oscillator can deliver two times of the output power obtained from one single oscillator at 220 GHz,2)the two EIOs can still deliver output signals with phase difference of O and when the currents of the two beams are different or the fabrication errors of the two EIO cavities are taken into account.The proposed scheme is promising in extending to phase locking between multiple EIOs,and generating higher power at millimeter-wave and higher frequencies.展开更多
The orientation effect of θʹ precipitates in stress-aged Al-Cu alloys has ambiguous interpretations. One view is that θʹ precipitates prefer to grow on the habit planes perpendicular to the applied compressive stres...The orientation effect of θʹ precipitates in stress-aged Al-Cu alloys has ambiguous interpretations. One view is that θʹ precipitates prefer to grow on the habit planes perpendicular to the applied compressive stress, while the other view suggests growth on habit planes parallel to the applied stress. In this study, stress-aged Al-4 wt.%Cu single crystal was sampled from three different <100>Al zone axes to observe the distribution of θʹ precipitates. A hybrid Monte-Carlo/ molecular dynamics simulations were used to investigate the orientation effect of θʹ precipitates. The simulation results are consistent with experimental observations and indicate that θʹ precipitates prefer to grow on the habit planes that are parallel to the direction of the applied compressive stress, not along the planes perpendicular to it. It is also found that 1/2<110> perfect dislocations are generated as θʹ precipitates plates grow thicker, and the reaction of 1/2<110> perfect dislocations decomposing into 1/6<112> Shockley dislocations lead to an increase in the length of θʹ precipitates. The former does not enhance the orientation effect, whereas the latter leads to a more significant orientation effect. Additionally, the degree of the orientation effect of θʹ precipitates is determined by the reduction of 1/2<110> dislocations with a positive correlation between them.展开更多
An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ) and a single Moving Plate(MP) is proposed in this article using both experimental and numerical approaches. First, an experimental set-up is p...An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ) and a single Moving Plate(MP) is proposed in this article using both experimental and numerical approaches. First, an experimental set-up is presented. Four collision tests have been performed: two tests in Backward Moving Plate(BMP) configuration, where the plate moves in opposition to jet, and two tests in Forward Moving Plate(FMP) configuration, where the plate moves alongside the jet. Based on the virtual origin approximation,a methodology(the Virtual Origin Method, VOM) is developed to extract quantities from the X-ray images, which serve as comparative data. γSPH simulations are carried out to complete the analysis, as they well capture the disturbance dynamics observed in the experiments. Based on these complementary experimental and numerical results, a new physical description is proposed through a detailed analysis of the interaction. It is shown that the SCJ/MP interaction is driven at first order by the contact geometry. Thus, BMP and FMP configurations do not generate the same disturbances because their local flow geometries are different. In the collision point frame of reference, the BMP flows in the same direction as the jet, causing its overall deflection. On the contrary, the FMP flow opposes that of the jet leading to an alternative creation of fragments and ligaments. An in-depth study, using the VOM shows that deflection angles, fragment-ligament creation frequencies, and deflection velocities evolve as the interaction progresses through slower jet elements.展开更多
The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Theref...The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Therefore,a good understanding of the interaction SCJ/MP is essential for improving both weapon and armor systems.In a previous article,we have shown that interaction regimes are mainly influenced by the local collision geometry.Thus,in the collision point frame,the angle of collision be-tween the continuous SCJ and the MP is a key parameter.This flow angle is acute for the Backward Moving plate(BMP)moving against the SCJ and obtuse for the Forward Moving Plate(FMP)moving alongside it.In the former,the jet is simply deflected,which is the regime 1 of deflection.In the latter,the interaction turns on an alternative creation of fragment and ligament,which is the regime 2.Fragments are parts of the jet that are only slightly deflected while ligaments are the curved material bridges that connect two consecutive fragments.When stretching,the jet is systematically subject to instabilities that disturb its surface,creating necks along it.Their growth finally leads to the jet fragmentation.In this article,we focus on this jet distur-bance and its consequences on the SCJ/MP interaction.An experimental set-up was built to implement the interaction between a SCJ and a moving plate for different collision points,at different stand-off distances.The plate can interact with a smooth SCJ or a disturbed SCJ at a close and a far stand-off distance,respectively.One of the main results is the visualization of a regime change in SCJ/BMP interaction.A regime 1(deflection)interaction changes into a ligament regime interaction(similar to a FMP regime 2)when the collision point stand-off is increased.It is proposed that this change can be attributed as the increase of the amplitude of the jet surface disturbances.This phenomenon is well captured by the gSPH simula-tions.Finally,using both experimental and numerical approaches,we propose a new detailed analysis of the different phenomena occurring during the interaction between a disturbed-surface jet and a moving plate.Interaction regime changes are linked to jet local geometry changes.The interactions of a BMP with a smooth SCJ or with a disturbed surface SCJ are geometrically not the same and,thus,generate different local flows and interaction mechanisms.However,some other simulations have been carried out with constant velocity jet whose surface has been previously disturbed.These simulations underline the influence of both disturbance wavelength l and amplitude A on the interaction regimes.Surface disturbances of the SCJ,linked to its stretching,have a major influence on its interaction with a moving plate.展开更多
To investigate the in vitro digestion and fermentation properties of soybean oligosaccharides(SBOS)extracted from defatted soybean meal,the changes in monosaccharide composition and molecular mass were analyzed.Subseq...To investigate the in vitro digestion and fermentation properties of soybean oligosaccharides(SBOS)extracted from defatted soybean meal,the changes in monosaccharide composition and molecular mass were analyzed.Subsequently,the effect of SBOS on microbial community structure and metabolites was studied by 16S rRNA gene sequencing and untargeted metabolomics based on liquid chromatography-mass spectrometry.Results showed that SBOS was not easily enzymolyzed during simulated digestion and could reach the large intestine through the digestive system.The significant decrease in the molecular mass of SBOS after in vitro fermentation indicated its utilization by the gut microbiota,which increased the contents of short-chain fatty acids and lactic acid,thereby reducing the pH of the fermentation broth.Moreover,the core community was found to consist of Blautia,Lactobacillaceae,and Pediococcus.SBOS up-regulated beneficial differential metabolites such as myo-inositol,lactose,and glucose,which were closely related to galactose,amino sugar,and nucleotide sugar metabolism.This study will provide a reference for exploring the relationship between the gut microbiota and the metabolites of SBOS,and provide a basis for the development and application of SBOS as an ingredient for functional products.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.
文摘To address the limitations of existing coupling methods in aero-engine system simulation,which fail to adaptively adjust iterative parameters and coupling relationships,which can result in low efficiency and in⁃stability,this study introduces a‘Dynamic Event-Driven Co-Simulation’algorithm integrated with decision tree algorithms.This algorithm separates the overall coupling relationships and the main solver from the primary mod⁃el,utilizing a dynamic event monitoring module to adaptively adjust simulation strategies,including iteration pa⁃rameters,coupling relationships,and convergence criteria.This facilitates efficient adaptive simulations of dy⁃namic events while balancing solution accuracy and computational efficiency.The research focuses on a twinshaft turbofan engine,establishing six system-level models that encompass overall performance and various sub⁃systems based on three coupling methods,along with a multidisciplinary multi-fidelity simulation framework in⁃corporating a 3D CFD nozzle model.The study tests both model exchange and coupled simulation methods under a 14 s transient acceleration and deceleration scenario.In a 100%throttle condition,a high-fidelity nozzle model is used to analyze the sensitivity of different convergence criteria on computational efficiency and accuracy.Re⁃sults indicate that the accuracy and efficiency achieved with this method are comparable to those of PROOSIS soft⁃ware(18 s and 35 s,respectively),while being 71%more efficient than Simulink software(62 s and 120 s,re⁃spectively).Furthermore,appropriately relaxing the convergence criteria for the 0D model(from 10-6 to 10-4)while enhancing those for the 3D model(from 3000 steps to 6000 steps)can effectively balance computational accuracy and efficiency.
基金This work was supported by the National Key Research and Development Program of China(2021YFA1301504)the Chinese Academy of Sciences Strategic Priority Research Program(XDB37040202)the National Natural Science Foundation of China(91953101).
文摘The assembly of a protein complex is very important for its biological function,which can be investigated by determining the order of assembly/disassembly of its protein subunits.Although static structures of many protein com-plexes are available in the protein data bank,their assembly/disassembly orders of subunits are largely unknown.In addition to experimental techniques for studying subcomplexes in the assembly/disassembly of a protein complex,computational methods can be used to predict the assembly/disassembly order.Since sampling is a nontrivial issue in simulating the assembly/disassembly process,coarse-grained simulations are more efficient than atomic simulations are.In this work,we developed computational protocols for predicting the assembly/disassembly orders of protein complexes via coarse-grained simulations.The protocols were illustrated via two protein complexes,and the predicted assembly/disassembly orders were consistent with the available experimental data.
基金financial support from National Natural Science Foundation of China(Grant No.12172325)。
文摘Porous materials are widely used in the field of protection because of their excellent energy absorption characteristics.In this work,a series of polyurethane microscopic models are established and the effect of porosity on the shock waves is studied with classical molecular dynamics simulations.Firstly,shock Hugoniot relations for different porosities are obtained,which compare well with the experimental data.The pores collapse and form local stress wave,which results in the complex multi-wave structure of the shock wave.The microstructure analysis shows that the local stress increases and the local velocity decreases gradually during the process of pore collapse to complete compaction.Finally,it leads to stress relaxation and velocity homogenization.The shock stress peaks can be fitted with two exponential functions,and the amplitude of attenuation coefficient decreases with the increase of density.Besides,the pore collapse under shock or non-shock are discussed by the entropy increase rate of the system.The energy is dissipated mainly through the multiple interactions of the waves under shock.The energy is dissipated mainly by the friction between atoms under non-shock.
基金supported by the NASA Heliospheric Theory Program under grant NNX08AI55G
文摘Both theory and simulation have played important roles in defining and illuminating the key mechanisms involved in substorms.Basic theories of magnetic reconnection and of interchange and ballooning instabilities were developed more than 50 years ago,and these plasma physical concepts have been central in discussions of substorm physics.A vast amount of research on reconnection,including both theoretical and computational studies,has helped provide a picture of how reconnection operates in the collisionless environment of the magnetosphere.Still,however,we do not fully understand how key microscale processes and large-scale dynamics work together to determine the location and rate of reconnection.While in the last twenty years,it has become clear that interchange processes are important for transporting plasma through the plasma sheet in the form of bursty bulk flows and substorm expansions,we still have not reached the point where simulations are able to realistically and defensibly represent all of the important aspects of the phenomenon.More than two decades ago it was suggested that the ballooning instability,the basic theory for which dates from the 1950s,may play an important role in substorms.Now the majority of experts agree that regions of the plasma sheet are often linearly unstable to ideal-MHD ballooning.However,it is also clear that kinetic effects introduce important modifications to the MHD stability criterion.It is still uncertain whether ballooning plays a leading role in substorms or has just a minor part.Among the different types of simulations that have been applied to the substorm problem,global MHD codes are unique in that,in a sense, they represent the entire global substorm phenomenon,including coupling to the solar wind and ionosphere, and the important mechanisms of reconnection,interchange,and ballooning.However,they have not yet progressed to the point where they can accurately represent the whole phenomenon,because grid-resolution problems limit the accuracy with which they can solve the equations of ideal MHD and the couphng to the ionosphere,and they cannot accurately represent small-scale processes that violate ideal MHD.
基金supported by the National Natural Science Foundation of China(Grant No.40102005 and No.49725205).
文摘Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.
基金supported by the National Natural Science Foundation of China(Grant No.11832006).
文摘A deep understanding of explosive sensitivities and their factors is important for safe and reliable applications.However,quantitative prediction of the sensitivities is difficult.Here,reactive molecular dynamics simulation models for high-speed piston impacts on explosive supercells were established.Simulations were also performed to investigate shock-induced reactions of various high-energy explosives.The fraction of reacted explosive molecules in an initial supercell changed linearly with the propagation distance of the shock-wave front.The corresponding slope could be used as a reaction rate for a specific shock-loading velocity.Reaction rates that varied with the shock-loading pressure exhibited two-stage linearities with different slopes.The two inflection points corresponded to the initial and accelerated reactions,which respectively correlated to the thresholds of shock-induced ignition and detonation.Therefore,the ignition and detonation critical pressures could be determined.The sensitivity could then be a quantitative prediction of the critical pressure.The accuracies of the quantitative shock sensitivity predictions were verified by comparing the impact and shock sensitivities of common explosives and the characteristics of anisotropic shock-induced reactions.Molecular dynamics simulations quantitatively predict and rank shock sensitivities by using only crystal structures of the explosives.Overall,this method will enable the design and safe use of explosives.
基金SupportedbytheNationalNaturalScienceFoundationofChina(No.20073042)TheNaturalScienceFoundationofAnhuiProvince (No .2 0 0 1kj2 63zc)
文摘A theoretical method to calculate multidimensional Franck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectroscopy of the anion O-3. Geometry optimization and harmonic vibrational frequency calculations have been performed on the AX～U4（）1A1 state of O3 and AX～U4（）2B1 state of O-3. Franck-Condon analyses and spectral simulation were carried out on the first photoelectron band of O-3. The theoretical spectrum obtained by employing CCSD（T）/6-311+G（2d,p） values are in excellent agreement with the observed one. In addition, the equilibrium geometry parameters, re（OO）= 0.135?5±0.000?5 nm and θe（O-O-O） =114.5±0.5°, of the AX～U4（）2B1 state of O-3, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation.
文摘Tube hydroforming process is a relative new process f or production of structural parts of low weight and high rigidity. The successfu lness of the process depends largely on the a proper selection of loading path w hich is axial feeding distance as related to the applied internal pressure. Due to the complicated nature of plastic deformation, a optimum loading path which w ill guarantee good hydroformed parts free of winkle and fracture has often to be determined by finite element analysis. In order to save trials and errors, adap tive FEM simulation method has been developed. To effectively apply the adaptive simulation method, we have to know the applicability of the method. In this pap er, a classification of tube hydroforming (THF) processes based on sensitivity to loading parameters has been suggested. Characteristics of the classification have been analyzed in terms of failure mode, dominant loading parameters and th eir working windows. It was discussed that the so called pressure dominant THF p rocess is the most difficult process for both simulation in FEM analysis and pra ctical operation in real manufacturing situation. To effectively find out the op timum loading path for pressure dominant THF process, adaptive FEM simulation st rategies are mostly needed.
基金Projects(51901248,51828102)supported by the National Natural Science Foundation of ChinaProject(2018JJ3649)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2019CX026)supported by the Innovation-driven Plan in Central South University,China。
文摘The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed(HCP)zirconium were investigated by molecular dynamics simulations,which were combined with experimental observation under high resolution transmission electron microscopy.The results show that externally applied loading first induced the HCP to body-centered cubic(BCC)phase transition in the Pitsch-Schrader(PS)orientation relationship(OR).Then,the face-centered cubic(FCC)structure transformed from the BCC phase in the Bain path.However,the HCP-to-BCC transition was incomplete at 100 K and 300 K,resulting in a prismatic-type OR between the FCC and original HCP phase.Additionally,at the temperature ranging from 100 K to 600 K,the inverse BCC-to-HCP transition occurred locally following other variants of the PS OR,resulting in a basal-type relation between the newly generated HCP and FCC phases.A higher tensile temperature promoted the amount of FCC phase transforming into the BCC phase when the strain exceeded 45%.Besides,the crystal stretched at lower temperatures exhibits relatively higher strength but by the compromise of plasticity.This study reveals the deformation mechanisms in HCP-Zr at different temperatures,which may provide a better understanding of the deformation mechanism of zirconium alloys under different application environments.
文摘Pressing process is a manufacturing method that obtained work piece with certain dimension, shape and capability through die forcing roughcast to produce plastic deformation or separate. This paper focuses on the key problems of visualization simulation in pressing die. The final aim is that numerical simulation system can simulate the process of processing forming technique, which can supply some necessary and accurate key parameters for die design. The detail description of mechanical characteristic and key technique of sheet forming technique is discussed. Pressing forming method is one of the most important forming techniques of metal forming, which has special mechanical characteristics. The character of sheet pressing forming is that the deformation of thickness direction is very small in contrast to other directions. The deformation mode of sheet forming mainly has the following kinds: bi-directional stretch, plane stress, stretches, depths extend, bending and counter-bending. The essence of press forming is the transferring course that the transferring region of rough comes to deformation by outside force, which is main researching principle in forming and the transferring field. The analysis of pressing forming course, disclose the feature of stress-strain and their changing rule, then pressing process and forming parameters could be obtained. So the states of force and deformation of transferring region is key to determine character about the varieties of pressing transferring. The paper analyzes these factors, which may influence forming precision in pressing process. In traditional methods, some key parameter such as spring-back, bending radius for die design are calculated by experience formula or select from data table. The paper brings forward the calculation methods of key parameter in the case of drawing finite element method and numerical simulation into pressing die design. In order to calculate the value of key parameters based on data supplied by FEM, a numerical simulation application is finished combined with two descriptions of work piece deformation NURBS and discrete piece. The numerical simulation is programmed on Microsoft Visual C++ with OpenGL as the graphics tool. It establishes numerical simulation program, dynamically simulates the process of sheet pressing figuration, and gets good effects.
文摘[Objective]This study aims to develop a thermodynamically consistent phase-field framework for modeling the initiation and evolution of discontinuous structures in geomaterials.[Methods]Our model introduces crack driving forces derived from the volumetric-deviatoric strain decomposition strategy,incorporating distinct tension,compression,and shear degradation mechanisms.Inertia effects capture compaction-band formation driven by wave-like disturbances,grain crushing,and frictional rearrangement.A monolithic algorithm ensures numerical stability and rapid convergence.[Results]The framework reproduces tensile,shear,mixed tensile-shear,and compressive-shear failures using the Benzeggagh-Kenane criterion.Validation against benchmark simulations-including uniaxial compression of rock-like and triaxial compression of V-notched sandstone specimens-demonstrates accurate predictions of crack initiation stress,localization orientation,and energy dissipation.[Conclusions]The framework provides a unified and robust numerical tool for analyzing the spatiotemporal evolution of strain localization and fracture in geomaterials.[Significance]By linking microscale fracture dynamics with macroscale failure within a thermodynamically consistent scheme,this study advances predictive modeling of rock stability,slope failure,and subsurface energy systems,contributing to safer and more sustainable geotechnical practice.
基金Supported in part by the National Natural Science Foundation of China(62401125)the Natural Science Foundation of Sichuan Province(2023NSFSC1376)the Fundamental Research Funds for the Central Universities(ZYGX2024J008)。
文摘In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-band.Two separate EIOs are coupled through a specific single-gap coupling field supported by a designed gap waveguide with length Lg,which form the phase-locked EIOs based on the commonly-resonated system.As a whole system,the system has been focused on with mode analysis based on different single-gap coupling fields,mode hopping,which present the variation of phase difference between the two-beam-wave interactions when changing Lg.To demonstrate the effectiveness of the proposed circuit system in producing the phase locking,we conducted particle-in-cell(PIC)simulations to show that the interesting mode hopping occurs with the phase difference of O and r between the output signals from two output ports,corresponding to the excitation of the TMn mode with different n.Simulation results show that 1)the oscillator can deliver two times of the output power obtained from one single oscillator at 220 GHz,2)the two EIOs can still deliver output signals with phase difference of O and when the currents of the two beams are different or the fabrication errors of the two EIO cavities are taken into account.The proposed scheme is promising in extending to phase locking between multiple EIOs,and generating higher power at millimeter-wave and higher frequencies.
基金Project(2023YFB3710503) supported by the National Key R&D Program of ChinaProject(52305439) supported by the National Natural Science Foundation of China。
文摘The orientation effect of θʹ precipitates in stress-aged Al-Cu alloys has ambiguous interpretations. One view is that θʹ precipitates prefer to grow on the habit planes perpendicular to the applied compressive stress, while the other view suggests growth on habit planes parallel to the applied stress. In this study, stress-aged Al-4 wt.%Cu single crystal was sampled from three different <100>Al zone axes to observe the distribution of θʹ precipitates. A hybrid Monte-Carlo/ molecular dynamics simulations were used to investigate the orientation effect of θʹ precipitates. The simulation results are consistent with experimental observations and indicate that θʹ precipitates prefer to grow on the habit planes that are parallel to the direction of the applied compressive stress, not along the planes perpendicular to it. It is also found that 1/2<110> perfect dislocations are generated as θʹ precipitates plates grow thicker, and the reaction of 1/2<110> perfect dislocations decomposing into 1/6<112> Shockley dislocations lead to an increase in the length of θʹ precipitates. The former does not enhance the orientation effect, whereas the latter leads to a more significant orientation effect. Additionally, the degree of the orientation effect of θʹ precipitates is determined by the reduction of 1/2<110> dislocations with a positive correlation between them.
基金supported by the Ministère des Armées,and the Agence de l'Innovation de Défense(AID).
文摘An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ) and a single Moving Plate(MP) is proposed in this article using both experimental and numerical approaches. First, an experimental set-up is presented. Four collision tests have been performed: two tests in Backward Moving Plate(BMP) configuration, where the plate moves in opposition to jet, and two tests in Forward Moving Plate(FMP) configuration, where the plate moves alongside the jet. Based on the virtual origin approximation,a methodology(the Virtual Origin Method, VOM) is developed to extract quantities from the X-ray images, which serve as comparative data. γSPH simulations are carried out to complete the analysis, as they well capture the disturbance dynamics observed in the experiments. Based on these complementary experimental and numerical results, a new physical description is proposed through a detailed analysis of the interaction. It is shown that the SCJ/MP interaction is driven at first order by the contact geometry. Thus, BMP and FMP configurations do not generate the same disturbances because their local flow geometries are different. In the collision point frame of reference, the BMP flows in the same direction as the jet, causing its overall deflection. On the contrary, the FMP flow opposes that of the jet leading to an alternative creation of fragments and ligaments. An in-depth study, using the VOM shows that deflection angles, fragment-ligament creation frequencies, and deflection velocities evolve as the interaction progresses through slower jet elements.
基金supported by the Ministère des Arméesthe Agence de l'Innovation de Défense (AID)
文摘The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Therefore,a good understanding of the interaction SCJ/MP is essential for improving both weapon and armor systems.In a previous article,we have shown that interaction regimes are mainly influenced by the local collision geometry.Thus,in the collision point frame,the angle of collision be-tween the continuous SCJ and the MP is a key parameter.This flow angle is acute for the Backward Moving plate(BMP)moving against the SCJ and obtuse for the Forward Moving Plate(FMP)moving alongside it.In the former,the jet is simply deflected,which is the regime 1 of deflection.In the latter,the interaction turns on an alternative creation of fragment and ligament,which is the regime 2.Fragments are parts of the jet that are only slightly deflected while ligaments are the curved material bridges that connect two consecutive fragments.When stretching,the jet is systematically subject to instabilities that disturb its surface,creating necks along it.Their growth finally leads to the jet fragmentation.In this article,we focus on this jet distur-bance and its consequences on the SCJ/MP interaction.An experimental set-up was built to implement the interaction between a SCJ and a moving plate for different collision points,at different stand-off distances.The plate can interact with a smooth SCJ or a disturbed SCJ at a close and a far stand-off distance,respectively.One of the main results is the visualization of a regime change in SCJ/BMP interaction.A regime 1(deflection)interaction changes into a ligament regime interaction(similar to a FMP regime 2)when the collision point stand-off is increased.It is proposed that this change can be attributed as the increase of the amplitude of the jet surface disturbances.This phenomenon is well captured by the gSPH simula-tions.Finally,using both experimental and numerical approaches,we propose a new detailed analysis of the different phenomena occurring during the interaction between a disturbed-surface jet and a moving plate.Interaction regime changes are linked to jet local geometry changes.The interactions of a BMP with a smooth SCJ or with a disturbed surface SCJ are geometrically not the same and,thus,generate different local flows and interaction mechanisms.However,some other simulations have been carried out with constant velocity jet whose surface has been previously disturbed.These simulations underline the influence of both disturbance wavelength l and amplitude A on the interaction regimes.Surface disturbances of the SCJ,linked to its stretching,have a major influence on its interaction with a moving plate.
文摘To investigate the in vitro digestion and fermentation properties of soybean oligosaccharides(SBOS)extracted from defatted soybean meal,the changes in monosaccharide composition and molecular mass were analyzed.Subsequently,the effect of SBOS on microbial community structure and metabolites was studied by 16S rRNA gene sequencing and untargeted metabolomics based on liquid chromatography-mass spectrometry.Results showed that SBOS was not easily enzymolyzed during simulated digestion and could reach the large intestine through the digestive system.The significant decrease in the molecular mass of SBOS after in vitro fermentation indicated its utilization by the gut microbiota,which increased the contents of short-chain fatty acids and lactic acid,thereby reducing the pH of the fermentation broth.Moreover,the core community was found to consist of Blautia,Lactobacillaceae,and Pediococcus.SBOS up-regulated beneficial differential metabolites such as myo-inositol,lactose,and glucose,which were closely related to galactose,amino sugar,and nucleotide sugar metabolism.This study will provide a reference for exploring the relationship between the gut microbiota and the metabolites of SBOS,and provide a basis for the development and application of SBOS as an ingredient for functional products.
