The homogeneity of aggregate blend has a significant influence on the performance of asphalt mixture.The composition of aggregate blend,including the size combination and the mass ratio between each size particles(MRE...The homogeneity of aggregate blend has a significant influence on the performance of asphalt mixture.The composition of aggregate blend,including the size combination and the mass ratio between each size particles(MRESP),is an important factor affecting the homogeneity.This study investigated the influence of the size combination and MRESP on the distribution homogeneity of particles in aggregate blend using discrete element method(DEM).An indicator quantifying the distribution homogeneity was established according to the coefficient of variation(CV)for particle number.Two-size,three-size,and four-size aggregate blends with various compositions were designed.Laboratory tests show the DEM simulation is feasible.The particle distribution homogeneity in various blends was analyzed.The results showed the distribution homogeneity of each size particles in a blend is closely related to their mass fraction.The higher the mass fraction of the particles,the more homogeneous the distribution of them.The MRESP has no significant influence on the homogeneity of the blend composed of only coarse aggregates.However,the homogeneity of the blend composed of coarse and fine aggregates improves gradually with the increase of the mass fraction of fine aggregates.The smaller the maximum particle size in a blend,the better the homogeneity.It is suggested that the mass fraction of fine aggregates should be between 33%and 50%for achieving good homogeneity of aggregate blends.The research results can provide a reference for gradation design of asphalt mixture.展开更多
A discontinuous smoothed particle hydrodynamics(DSPH)method considering block contacts is originally developed to model the cracking,frictional slip and large deformation in rock masses,and is verified by theoretical,...A discontinuous smoothed particle hydrodynamics(DSPH)method considering block contacts is originally developed to model the cracking,frictional slip and large deformation in rock masses,and is verified by theoretical,numerical and/or experimental results.In the DSPH method,cracking is realized by breaking the virtual bonds via a pseudo-spring method based on Mohr–Coulomb failure criteria.The damaged particles are instantaneously replaced by discontinuous particles and the contact bond between the original and discontinuous particles is formed to simulate the frictional slip and separation/contraction between fracture surfaces based on the block contact algorithm.The motion of rock blocks and the contact force of discontinuous particles are determined following Newton's second law.The results indicate that the DSPH method precisely captures the cracking,contact formation and complete failure across six numerical benchmark tests.This single smoothed particle hydrodynamics(SPH)framework could significantly improve computational efficiency and is potentially applicable to broad multi-physical rock engineering problems of different scales.展开更多
The Vortex Particle Method(VPM)is a meshless Lagrangian vortex method.Its low numerical dissipation is exceptionally suitable for wake simulation.Nevertheless,the inadequate numerical stability of VPM prevents its wid...The Vortex Particle Method(VPM)is a meshless Lagrangian vortex method.Its low numerical dissipation is exceptionally suitable for wake simulation.Nevertheless,the inadequate numerical stability of VPM prevents its widespread application in high Reynolds number flow and shear turbulence.To better simulate these flows,this paper proposes the stability-enhanced VPM based on a Reformulated VPM(RVPM)constrained by conservation of angular momentum,integrating a relaxation scheme to suppress the divergence of the vorticity field,and further coupling the Sub-Grid Scale(SGS)model to account for the turbulence dissipation caused by vortex advection and vortex stretching.The validity of the RVPM is confirmed by simulating an isolated vortex ring's evolution.The results also demonstrate that the relaxation scheme of vorticity enhances the numerical stability of the VPM by mitigating the divergence of the vorticity field.The leapfrogging vortex rings simulation demonstrates that the RVPM with the present SGS model can more precisely feature the leapfrog and fusion of vortex rings and has improved numerical stability in high Reynolds number flows.The round turbulent jet simulation confirms that the stability-enhanced VPM can stably simulate shear turbulence and accurately resolve fluctuating components and Reynolds stresses in the turbulence.展开更多
We present a hybrid smoothed particle magnetohydrodynamics(SPMHD)code integrating smoothed particle hydrodynamics(SPH)and finite element methods(FEM)to simulate coupled fluid-electromagnetic phenomena.The framework em...We present a hybrid smoothed particle magnetohydrodynamics(SPMHD)code integrating smoothed particle hydrodynamics(SPH)and finite element methods(FEM)to simulate coupled fluid-electromagnetic phenomena.The framework employs SPH for fluid dynamics,addressing large deformations,shocks,and plasma behavior,while FEM resolves electromagnetic fields via Maxwell's equations for magnetic vector and electric scalar potentials,ensuring divergence-free conditions and global current density calculations in conductive region.Operator splitting method couples these modules,enabling real-time integration of magnetic,electric,thermal,and fluid fields.Benchmark tests validate the code against analytical solutions and existing models,including blow-by instability simulations that demonstrate the method's accuracy in capturing fluid-magnetic interactions.Designed for 3D applications,SPMHD offers robust scalability across multiprocessor architectures,establishing it as a versatile tool for plasma physics research.展开更多
In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a gene...In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner(HR)variational principle,creating an implicit PFEM formulation.To mitigate the volumetric locking issue in low-order elements,we employ a node-based strain smoothing technique.By discretising field variables at the centre of smoothing cells,we achieve nodal integration over cells,eliminating the need for sophisticated mapping operations after re-meshing in the PFEM.We express the discretised governing equations as a min-max optimisation problem,which is further reformulated as a standard second-order cone programming(SOCP)problem.Stresses,pore water pressure,and displacements are simultaneously determined using the advanced primal-dual interior point method.Consequently,our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation.Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy,obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches.This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.展开更多
In the field of discretization-based meshfree/meshless methods,the improvements in the higher-order consistency,stability,and computational efficiency are of great concerns in computational science and numerical solut...In the field of discretization-based meshfree/meshless methods,the improvements in the higher-order consistency,stability,and computational efficiency are of great concerns in computational science and numerical solutions to partial differential equations.Various alternative numerical methods of the finite particle method(FPM)frame have been extended from mathematical theories to numerical applications separately.As a comprehensive numerical scheme,this study suggests a unified resolved program for numerically investigating their accuracy,stability,consistency,computational efficiency,and practical applicability in industrial engineering contexts.The high-order finite particle method(HFPM)and corrected methods based on the multivariate Taylor series expansion are constructed and analyzed to investigate the whole applicability in different benchmarks of computational fluid dynamics.Specifically,four benchmarks are designed purposefully from statical exact solutions to multifaceted hydrodynamic tests,which possess different numerical performances on the particle consistency,numerical discretized forms,particle distributions,and transient time evolutional stabilities.This study offers a numerical reference for the current unified resolved program.展开更多
Particle morphology is critical in affecting the crushing behavior of rockfill materials.In contrast,most current single particle simulations lack satisfactory morphology accuracy,and the resulting crushing modes devi...Particle morphology is critical in affecting the crushing behavior of rockfill materials.In contrast,most current single particle simulations lack satisfactory morphology accuracy,and the resulting crushing modes deviate from observations to some extent.Therefore,we reconstruct the real particle morphology with the spherical harmonic(SH)method and employ the finite-discrete element method(FDEM)to simulate the one-dimensional(1D)compressive crushing process of basalt particles commonly used in rockfill.The influences of four main morphological parameters,i.e.sphericity,aspect ratio,roundness,and convexity,on the single particle strength and the crushing modes are discussed.The results show that with the SH degree set to 15 and a mesh number of 20,480,the FDEM models of reconstructed particles achieve sufficient morphology accuracy and high computational efficiency.Based on the model,the simulation results demonstrate that the aspect ratio has the most significant impact on single particle strength,followed by sphericity.In contrast,roundness and convexity have a weaker effect than the above two parameters.Also,it is revealed that single particle strength decreases with increasing aspect ratio and sphericity,while it increases with higher roundness and convexity.Furthermore,aspect ratio significantly changes the initial crushing position,sphericity dominates post-crushing fragment size and quantity,and roundness mainly affects post-crushing morphology.The model results have been employed in establishing a support vector regression(SVR)-based predicted model,exhibiting good predictive performance and advantages for the optimization of rockfill particles in engineering.展开更多
The motion of an elliptical rigid particle in a lid-driven cavity flow was numerically simulated using the immersed boundary lattice Boltzmann method(IB-LBM).The effects of the particle's initial orientation angle...The motion of an elliptical rigid particle in a lid-driven cavity flow was numerically simulated using the immersed boundary lattice Boltzmann method(IB-LBM).The effects of the particle's initial orientation angle,initial position,aspect ratio,and size on the motion characteristics were investigated.The computational results indicate that the particle's motion undergoes two distinct stages:a starting stage that involves moving from the release position to a limit cycle,and a periodic stage that involves moving on the limit cycle.The initial orientation of the particle has a minimal impact on both stages of motion.In contrast,the time it takes for the particle to reach the limit cycle may vary depending on the release position.Furthermore,particles with a larger aspect ratio exhibit a greater maximum velocity magnitude;an increase in particle size causes the particle trajectory to contract more toward the center of the cavity,decreasing the centrifugal force experienced by the particle.展开更多
The present study investigates the infiuences of aorta geometry on hemodynamics and material transport.Based on the observation of the human aorta.two geometric paramelers are examined for a model aorta,savine the ane...The present study investigates the infiuences of aorta geometry on hemodynamics and material transport.Based on the observation of the human aorta.two geometric paramelers are examined for a model aorta,savine the anele spanned by the main aorticarc and the diameter of the descending aorta.irect numerical simulations are conducted for nine model aortas with difierencombinations of aorta arc and outlet diameter.Results reveal that the outlet diameter has a sienificant impact on aorta hemodynamics.A smaller outlet diameter compared to the inlet leads to accelerated blood fow in the descending segment,affecting fiowmorphology including the vortex structures,and increasing peak pressure gradient and wall shear stress.However,it reducesthe oscillatory shear index,indicating a more organized fow.Analyses show faster particle transport and reduced accumulativeresidence time for smaller outlet diameters,The arc anele has less sieniicant efiects on these properties.except for delaying thetime to reach the maximum pressure gradient during cjection.The research results may suggest that the diameter of the aorticoutlet has a greater impact on the fiow structures,while the arc angle has a relatively less efiect.These findings provide insightsinto the relation between hemodynamics and aorta geometry,with potential clinical implications.展开更多
Hard-magnetic soft materials exhibit significant shape morphing capabilities under non-contact magnetic actuation, yet their particulate composition tends to compromise material toughness. To quantify particle-matrix ...Hard-magnetic soft materials exhibit significant shape morphing capabilities under non-contact magnetic actuation, yet their particulate composition tends to compromise material toughness. To quantify particle-matrix interactions, we present a mechanics model describing the energy functional of planar magnetic composites. Through the Fourier series, the analytical solutions for stress distribution and interfacial peeling length of a single particle-polymer unit are derived with the Rayleigh-Ritz method under uniaxial tension. The calculated results of stress fields without the magnetic field agree well with those of the finite element method. The effects of external magnetic field strength and particle content on the stress distribution and peeling length are fully explored, and the enhanced analytical outcomes are obtained through numerical prediction.These insights can be used to validate the reliability of engineering designs, including adaptive structures, micro-electro-mechanical sensors, and soft robotic systems.展开更多
Utilizing the Discrete Element Method,this research studied the stiffness distribution of gap-graded soils by modifying the conventional static method.By acknowledging the inherent particle property disparity between ...Utilizing the Discrete Element Method,this research studied the stiffness distribution of gap-graded soils by modifying the conventional static method.By acknowledging the inherent particle property disparity between coarser and finer particles,this research differentiates the stiffness distribution of gap-graded soils from the perspective of contact and particle types.Results indicate that particle property disparity significantly influence the small-strain stiffness characteristics,consequently altering the overall stiffness distribution in gap-graded soil specimens.Specifically,with the equivalent coarser particle property,an increase in particle Young's modulus of finer particles results in an augmentation of small-strain stiffness values,alongside an increased stiffness distribution contribution from finer particles.Nevertheless,this study reveals that even with a higher particle Young's modulus of finer particles,the proportion of small-strain stiffness transferred by finer particles remains consistently lower than their volume fraction.Furthermore,the proportion of stiffness transferred by finer particles may fall below their contribution to stress transmission.This investigation accentuates the subtle yet significant effects of particle property variations on small strain stiffness and its subsequent distribution,providing a foundation for advancing the significance of particle property disparities in evaluating soil responses.展开更多
Using traditional particle tracking velocimetry based on optical flow for measuring areas with large velocity gradient changes may cause oversmoothing,resulting in significant measurement errors.To address this proble...Using traditional particle tracking velocimetry based on optical flow for measuring areas with large velocity gradient changes may cause oversmoothing,resulting in significant measurement errors.To address this problem,the traditional particle tracking velocimetry method based on an optical flow was improved.The level set segmentation algorithm was used to obtain the boundary contour of the region with large velocity gradient changes,and the non-uniform flow field was divided into regions according to the boundary contour to obtain sub-regions with uniform velocity distribution.The particle tracking velocimetry method based on optical flow was used to measure the granular flow velocity in each sub-region,thus avoiding the problem of granular flow distribution.The simulation results show that the measurement accuracy of this method is approximately 10%higher than that of traditional methods.The method was applied to a velocity measurement experiment on dense granular flow in silos,and the velocity distribution of the granular flow was obtained,verifying the practicality of the method in granular flow fields.展开更多
Neutron shielding materials face imbalanced behaviors among shielding,strength,and ductility properties.Based on the requirement of the high property shielding particles,a superior semi-coherentτ(Al4 MgGd)phase was d...Neutron shielding materials face imbalanced behaviors among shielding,strength,and ductility properties.Based on the requirement of the high property shielding particles,a superior semi-coherentτ(Al4 MgGd)phase was designed and predicted by cluster expansion(CE)method using density functional theory calculations.To realize its shielding property,the Powder Metallurgy-based routines(i.e.,powder fabrication,spark plasma sintering,and hot extrusion techniques)are used to fabricate 6TiB_(2)/Al-6Mg-5Gd(wt.%)composite with dispersed refinedτphases and homogenized TiB_(2) distribution.The atomic structure of ternary phase τ is examined by aberration-corrected high-angle annual dark-field(HAADF)scanning transmission electron microscope(STEM)and energy dispersive X-ray spectroscopy(EDXS)STEM experiments,which is well complied with the calculated compound(Al_(4)MgGd).In detail,theτ(Al_(4)MgGd)phase has a semi-coherent interface both with α-Al and TiB_(2),which is consistent with the prediction of interface relationships.With the optimized interfaces,the TiB_(2) and τ phases can effectively promote recrystallization and suppress grain growth,leading to the formation of ultra-fine grain structure.Then,the composite exhibits advanced shielding properties(Macroscopic transmission cross section ~24.1/cm,higher than 30%B_(4) C/Al)and optimized synergic mechanical properties(Ultimate tensile strength ~506 MPa,elongation ~12.9%),which are far higher than available Al-based neutron shielding materials.Finally,the underlying strength-ductility mechanisms are discussed.Critically,the design and optimization of shielding particle interfaces are reliable strategies for developing novel structural-functional integrated materials.展开更多
In this study,a common-node DEM-SPH coupling model based on the shared node method is proposed,and a fluid–structure coupling method using the common-node discrete element method-smoothed particle hydrodynamics(DS-SP...In this study,a common-node DEM-SPH coupling model based on the shared node method is proposed,and a fluid–structure coupling method using the common-node discrete element method-smoothed particle hydrodynamics(DS-SPH)method is developed using LS-DYNA software.The DEM and SPH are established on the same node to create common-node DEM-SPH particles,allowing for fluid–structure interactions.Numerical simulations of various scenarios,including water entry of a rigid sphere,dam-break propagation over wet beds,impact on an ice plate floating on water and ice accumulation on offshore structures,are conducted.The interaction between DS particles and SPH fluid and the crack generation mechanism and expansion characteristics of the ice plate under the interaction of structure and fluid are also studied.The results are compared with available data to verify the proposed coupling method.Notably,the simulation results demonstrated that controlling the cutoff pressure of internal SPH particles could effectively control particle splashing during ice crushing failure.展开更多
Viscoelastic flows play an important role in numerous engineering fields,and the multiscale algorithms for simulating viscoelastic flows have received significant attention in order to deepen our understanding of the ...Viscoelastic flows play an important role in numerous engineering fields,and the multiscale algorithms for simulating viscoelastic flows have received significant attention in order to deepen our understanding of the nonlinear dynamic behaviors of viscoelastic fluids.However,traditional grid-based multiscale methods are confined to simple viscoelastic flows with short relaxation time,and there is a lack of uniform multiscale scheme available for coupling different solvers in the simulations of viscoelastic fluids.In this paper,a universal multiscale method coupling an improved smoothed particle hydrodynamics(SPH)and multiscale universal interface(MUI)library is presented for viscoelastic flows.The proposed multiscale method builds on an improved SPH method and leverages the MUI library to facilitate the exchange of information among different solvers in the overlapping domain.We test the capability and flexibility of the presented multiscale method to deal with complex viscoelastic flows by solving different multiscale problems of viscoelastic flows.In the first example,the simulation of a viscoelastic Poiseuille flow is carried out by two coupled improved SPH methods with different spatial resolutions.The effects of exchanging different physical quantities on the numerical results in both the upper and lower domains are also investigated as well as the absolute errors in the overlapping domain.In the second example,the complex Wannier flow with different Weissenberg numbers is further simulated by two improved SPH methods and coupling the improved SPH method and the dissipative particle dynamics(DPD)method.The numerical results show that the physical quantities for viscoelastic flows obtained by the presented multiscale method are in consistence with those obtained by a single solver in the overlapping domain.Moreover,transferring different physical quantities has an important effect on the numerical results.展开更多
An h-adaptivity analysis scheme based on multiple scale reproducing kernel particle method was proposed, and two node refinement strategies were constructed using searching-neighbor-nodes(SNN) and local-Delaunay-trian...An h-adaptivity analysis scheme based on multiple scale reproducing kernel particle method was proposed, and two node refinement strategies were constructed using searching-neighbor-nodes(SNN) and local-Delaunay-triangulation(LDT) tech-niques, which were suitable and effective for h-adaptivity analysis on 2-D problems with the regular or irregular distribution of the nodes. The results of multiresolution and h-adaptivity analyses on 2-D linear elastostatics and bending plate problems demonstrate that the improper high-gradient indicator will reduce the convergence property of the h-adaptivity analysis, and that the efficiency of the LDT node refinement strategy is better than SNN, and that the presented h-adaptivity analysis scheme is provided with the validity, stability and good convergence property.展开更多
The compaction quality of subgrade filler strongly affects subgrade settlement.The main objective of this research is to analyze the macro-and micro-mechanical compaction characteristics of subgrade filler based on th...The compaction quality of subgrade filler strongly affects subgrade settlement.The main objective of this research is to analyze the macro-and micro-mechanical compaction characteristics of subgrade filler based on the real shape of coarse particles.First,an improved Viola-Jones algorithm is employed to establish a digitalized 2D particle database for coarse particle shape evaluation and discrete modeling purposes of subgrade filler.Shape indexes of 2D subgrade filler are then computed and statistically analyzed.Finally,numerical simulations are performed to quantitatively investigate the effects of the aspect ratio(AR)and interparticle friction coefficient(μ)on the macro-and micro-mechanical compaction characteristics of subgrade filler based on the discrete element method(DEM).The results show that with the increasing AR,the coarse particles are narrower,leading to the increasing movement of fine particles during compaction,which indicates that it is difficult for slender coarse particles to inhibit the migration of fine particles.Moreover,the average displacement of particles is strongly influenced by the AR,indicating that their occlusion under power relies on particle shapes.The dis-placement and velocity of fine particles are much greater than those of the coarse particles,which shows that compaction is primarily a migration of fine particles.Under the cyclic load,the interparticle friction coefficientμhas little effect on the internal structure of the sample;under the quasi-static loads,however,the increase inμwill lead to a significant increase in the porosity of the sample.This study could not only provide a novel approach to investigate the compaction mechanism but also establish a new theoretical basis for the evaluation of intelligent subgrade compaction.展开更多
Hydrothermal method was used to synthesize nanoscale particles of MnZn ferrites. The crystallites were characterized by XRD, TEM and SEM. The effects of the reaction time, temperature and additives on the product were...Hydrothermal method was used to synthesize nanoscale particles of MnZn ferrites. The crystallites were characterized by XRD, TEM and SEM. The effects of the reaction time, temperature and additives on the product were investigated. Crystallization process would be carried out above 160 ℃ for 5 h or more, higher temperature can reduce the reaction time. Additives were used to remove impurities such as Fe 2O 3, ZnMnO 3.10～15 nm pure slightly agglomerated MnZn ferrite crystallites with a narrow grain size distribution were obtained.展开更多
Multibody system dynamics provides a strong tool for the estimation of dynamic performances and the optimization of multisystem robot design. It can be described with differential algebraic equations(DAEs). In this pa...Multibody system dynamics provides a strong tool for the estimation of dynamic performances and the optimization of multisystem robot design. It can be described with differential algebraic equations(DAEs). In this paper, a particle swarm optimization(PSO) method is introduced to solve and control a symplectic multibody system for the first time. It is first combined with the symplectic method to solve problems in uncontrolled and controlled robotic arm systems. It is shown that the results conserve the energy and keep the constraints of the chaotic motion, which demonstrates the efficiency, accuracy, and time-saving ability of the method. To make the system move along the pre-planned path, which is a functional extremum problem, a double-PSO-based instantaneous optimal control is introduced. Examples are performed to test the effectiveness of the double-PSO-based instantaneous optimal control. The results show that the method has high accuracy, a fast convergence speed, and a wide range of applications.All the above verify the immense potential applications of the PSO method in multibody system dynamics.展开更多
An h-adaptivity analysis scheme based on multiple scale reproducing kernel particle method was proposed, and two node refinement strategies were constructed using searching-neighbor-nodes（SNN） and local-Delaunay-tri...An h-adaptivity analysis scheme based on multiple scale reproducing kernel particle method was proposed, and two node refinement strategies were constructed using searching-neighbor-nodes（SNN） and local-Delaunay-triangulation（LDT） techniques, which were suitable and effective for h-adaptivity analysis on 2-D problems with the regular or irregular distribution of the nodes. The results of multiresolution and h- adaptivity analyses on 2-D linear elastostatics and bending plate problems demonstrate that the improper high-gradient indicator will reduce the convergence property of the h- adaptivity analysis, and that the efficiency of the LDT node refinement strategy is better than SNN, and that the presented h-adaptivity analysis scheme is provided with the validity, stability and good convergence property.展开更多
基金funded by the National Natural Science Foundation of China(No.51978048).
文摘The homogeneity of aggregate blend has a significant influence on the performance of asphalt mixture.The composition of aggregate blend,including the size combination and the mass ratio between each size particles(MRESP),is an important factor affecting the homogeneity.This study investigated the influence of the size combination and MRESP on the distribution homogeneity of particles in aggregate blend using discrete element method(DEM).An indicator quantifying the distribution homogeneity was established according to the coefficient of variation(CV)for particle number.Two-size,three-size,and four-size aggregate blends with various compositions were designed.Laboratory tests show the DEM simulation is feasible.The particle distribution homogeneity in various blends was analyzed.The results showed the distribution homogeneity of each size particles in a blend is closely related to their mass fraction.The higher the mass fraction of the particles,the more homogeneous the distribution of them.The MRESP has no significant influence on the homogeneity of the blend composed of only coarse aggregates.However,the homogeneity of the blend composed of coarse and fine aggregates improves gradually with the increase of the mass fraction of fine aggregates.The smaller the maximum particle size in a blend,the better the homogeneity.It is suggested that the mass fraction of fine aggregates should be between 33%and 50%for achieving good homogeneity of aggregate blends.The research results can provide a reference for gradation design of asphalt mixture.
基金financial support from the National Key Research and Development Program of China(Grant No.2019YFC1509702)the Fundamental Research Funds for the Central Universities in Chinathe National Natural Science Foundation of China(Grant No.42377162).
文摘A discontinuous smoothed particle hydrodynamics(DSPH)method considering block contacts is originally developed to model the cracking,frictional slip and large deformation in rock masses,and is verified by theoretical,numerical and/or experimental results.In the DSPH method,cracking is realized by breaking the virtual bonds via a pseudo-spring method based on Mohr–Coulomb failure criteria.The damaged particles are instantaneously replaced by discontinuous particles and the contact bond between the original and discontinuous particles is formed to simulate the frictional slip and separation/contraction between fracture surfaces based on the block contact algorithm.The motion of rock blocks and the contact force of discontinuous particles are determined following Newton's second law.The results indicate that the DSPH method precisely captures the cracking,contact formation and complete failure across six numerical benchmark tests.This single smoothed particle hydrodynamics(SPH)framework could significantly improve computational efficiency and is potentially applicable to broad multi-physical rock engineering problems of different scales.
基金co-supported by the National Natural Science Foundation of China(No.12402272)the Natural Science Basic Research Program of Shaanxi Province,China(No.2024JC-YBQN-0024)the Fundamental Research Funds for the Central Universities,China(No.D5000240030)。
文摘The Vortex Particle Method(VPM)is a meshless Lagrangian vortex method.Its low numerical dissipation is exceptionally suitable for wake simulation.Nevertheless,the inadequate numerical stability of VPM prevents its widespread application in high Reynolds number flow and shear turbulence.To better simulate these flows,this paper proposes the stability-enhanced VPM based on a Reformulated VPM(RVPM)constrained by conservation of angular momentum,integrating a relaxation scheme to suppress the divergence of the vorticity field,and further coupling the Sub-Grid Scale(SGS)model to account for the turbulence dissipation caused by vortex advection and vortex stretching.The validity of the RVPM is confirmed by simulating an isolated vortex ring's evolution.The results also demonstrate that the relaxation scheme of vorticity enhances the numerical stability of the VPM by mitigating the divergence of the vorticity field.The leapfrogging vortex rings simulation demonstrates that the RVPM with the present SGS model can more precisely feature the leapfrog and fusion of vortex rings and has improved numerical stability in high Reynolds number flows.The round turbulent jet simulation confirms that the stability-enhanced VPM can stably simulate shear turbulence and accurately resolve fluctuating components and Reynolds stresses in the turbulence.
基金supported by the Major National Science and Technology Infrastructure(No.2208-000000-04-01249628)the Shanghai Science and Technology Commission(No.21DZ1206500)。
文摘We present a hybrid smoothed particle magnetohydrodynamics(SPMHD)code integrating smoothed particle hydrodynamics(SPH)and finite element methods(FEM)to simulate coupled fluid-electromagnetic phenomena.The framework employs SPH for fluid dynamics,addressing large deformations,shocks,and plasma behavior,while FEM resolves electromagnetic fields via Maxwell's equations for magnetic vector and electric scalar potentials,ensuring divergence-free conditions and global current density calculations in conductive region.Operator splitting method couples these modules,enabling real-time integration of magnetic,electric,thermal,and fluid fields.Benchmark tests validate the code against analytical solutions and existing models,including blow-by instability simulations that demonstrate the method's accuracy in capturing fluid-magnetic interactions.Designed for 3D applications,SPMHD offers robust scalability across multiprocessor architectures,establishing it as a versatile tool for plasma physics research.
基金supported by the Swiss National Science Foundation(Grant No.189882)the National Natural Science Foundation of China(Grant No.41961134032)support provided by the New Investigator Award grant from the UK Engineering and Physical Sciences Research Council(Grant No.EP/V012169/1).
文摘In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner(HR)variational principle,creating an implicit PFEM formulation.To mitigate the volumetric locking issue in low-order elements,we employ a node-based strain smoothing technique.By discretising field variables at the centre of smoothing cells,we achieve nodal integration over cells,eliminating the need for sophisticated mapping operations after re-meshing in the PFEM.We express the discretised governing equations as a min-max optimisation problem,which is further reformulated as a standard second-order cone programming(SOCP)problem.Stresses,pore water pressure,and displacements are simultaneously determined using the advanced primal-dual interior point method.Consequently,our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation.Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy,obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches.This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.
基金supported by the National Natural Science Foundation of China(No.12002290)。
文摘In the field of discretization-based meshfree/meshless methods,the improvements in the higher-order consistency,stability,and computational efficiency are of great concerns in computational science and numerical solutions to partial differential equations.Various alternative numerical methods of the finite particle method(FPM)frame have been extended from mathematical theories to numerical applications separately.As a comprehensive numerical scheme,this study suggests a unified resolved program for numerically investigating their accuracy,stability,consistency,computational efficiency,and practical applicability in industrial engineering contexts.The high-order finite particle method(HFPM)and corrected methods based on the multivariate Taylor series expansion are constructed and analyzed to investigate the whole applicability in different benchmarks of computational fluid dynamics.Specifically,four benchmarks are designed purposefully from statical exact solutions to multifaceted hydrodynamic tests,which possess different numerical performances on the particle consistency,numerical discretized forms,particle distributions,and transient time evolutional stabilities.This study offers a numerical reference for the current unified resolved program.
基金financial support to this study from the National Natural Science Foundation of China,NSFC(Grant No.52278367).
文摘Particle morphology is critical in affecting the crushing behavior of rockfill materials.In contrast,most current single particle simulations lack satisfactory morphology accuracy,and the resulting crushing modes deviate from observations to some extent.Therefore,we reconstruct the real particle morphology with the spherical harmonic(SH)method and employ the finite-discrete element method(FDEM)to simulate the one-dimensional(1D)compressive crushing process of basalt particles commonly used in rockfill.The influences of four main morphological parameters,i.e.sphericity,aspect ratio,roundness,and convexity,on the single particle strength and the crushing modes are discussed.The results show that with the SH degree set to 15 and a mesh number of 20,480,the FDEM models of reconstructed particles achieve sufficient morphology accuracy and high computational efficiency.Based on the model,the simulation results demonstrate that the aspect ratio has the most significant impact on single particle strength,followed by sphericity.In contrast,roundness and convexity have a weaker effect than the above two parameters.Also,it is revealed that single particle strength decreases with increasing aspect ratio and sphericity,while it increases with higher roundness and convexity.Furthermore,aspect ratio significantly changes the initial crushing position,sphericity dominates post-crushing fragment size and quantity,and roundness mainly affects post-crushing morphology.The model results have been employed in establishing a support vector regression(SVR)-based predicted model,exhibiting good predictive performance and advantages for the optimization of rockfill particles in engineering.
文摘The motion of an elliptical rigid particle in a lid-driven cavity flow was numerically simulated using the immersed boundary lattice Boltzmann method(IB-LBM).The effects of the particle's initial orientation angle,initial position,aspect ratio,and size on the motion characteristics were investigated.The computational results indicate that the particle's motion undergoes two distinct stages:a starting stage that involves moving from the release position to a limit cycle,and a periodic stage that involves moving on the limit cycle.The initial orientation of the particle has a minimal impact on both stages of motion.In contrast,the time it takes for the particle to reach the limit cycle may vary depending on the release position.Furthermore,particles with a larger aspect ratio exhibit a greater maximum velocity magnitude;an increase in particle size causes the particle trajectory to contract more toward the center of the cavity,decreasing the centrifugal force experienced by the particle.
基金the support of the Clinical Medicine Plus X-Young Scholars Project at Peking University for thiswork.
文摘The present study investigates the infiuences of aorta geometry on hemodynamics and material transport.Based on the observation of the human aorta.two geometric paramelers are examined for a model aorta,savine the anele spanned by the main aorticarc and the diameter of the descending aorta.irect numerical simulations are conducted for nine model aortas with difierencombinations of aorta arc and outlet diameter.Results reveal that the outlet diameter has a sienificant impact on aorta hemodynamics.A smaller outlet diameter compared to the inlet leads to accelerated blood fow in the descending segment,affecting fiowmorphology including the vortex structures,and increasing peak pressure gradient and wall shear stress.However,it reducesthe oscillatory shear index,indicating a more organized fow.Analyses show faster particle transport and reduced accumulativeresidence time for smaller outlet diameters,The arc anele has less sieniicant efiects on these properties.except for delaying thetime to reach the maximum pressure gradient during cjection.The research results may suggest that the diameter of the aorticoutlet has a greater impact on the fiow structures,while the arc angle has a relatively less efiect.These findings provide insightsinto the relation between hemodynamics and aorta geometry,with potential clinical implications.
基金supported by the National Natural Science Foundation of China (Nos. 11972375 and12211530028)the Special Funds for the Basic Scientific Research Expenses of Central Government Universities of China (No. 2472022X03006A)
文摘Hard-magnetic soft materials exhibit significant shape morphing capabilities under non-contact magnetic actuation, yet their particulate composition tends to compromise material toughness. To quantify particle-matrix interactions, we present a mechanics model describing the energy functional of planar magnetic composites. Through the Fourier series, the analytical solutions for stress distribution and interfacial peeling length of a single particle-polymer unit are derived with the Rayleigh-Ritz method under uniaxial tension. The calculated results of stress fields without the magnetic field agree well with those of the finite element method. The effects of external magnetic field strength and particle content on the stress distribution and peeling length are fully explored, and the enhanced analytical outcomes are obtained through numerical prediction.These insights can be used to validate the reliability of engineering designs, including adaptive structures, micro-electro-mechanical sensors, and soft robotic systems.
基金Financial supports from the PolyU Distinguished Postdoctoral Fellowship Scheme are highly appreciatedsupported by the National Natural Science Foundation of China (Grant No.52201008)the Fundamental Research Funds for the Central Universities,the State Key Laboratory of Particle Detection and Electronics (Grant No.SKLPDE-KF-202311).
文摘Utilizing the Discrete Element Method,this research studied the stiffness distribution of gap-graded soils by modifying the conventional static method.By acknowledging the inherent particle property disparity between coarser and finer particles,this research differentiates the stiffness distribution of gap-graded soils from the perspective of contact and particle types.Results indicate that particle property disparity significantly influence the small-strain stiffness characteristics,consequently altering the overall stiffness distribution in gap-graded soil specimens.Specifically,with the equivalent coarser particle property,an increase in particle Young's modulus of finer particles results in an augmentation of small-strain stiffness values,alongside an increased stiffness distribution contribution from finer particles.Nevertheless,this study reveals that even with a higher particle Young's modulus of finer particles,the proportion of small-strain stiffness transferred by finer particles remains consistently lower than their volume fraction.Furthermore,the proportion of stiffness transferred by finer particles may fall below their contribution to stress transmission.This investigation accentuates the subtle yet significant effects of particle property variations on small strain stiffness and its subsequent distribution,providing a foundation for advancing the significance of particle property disparities in evaluating soil responses.
文摘Using traditional particle tracking velocimetry based on optical flow for measuring areas with large velocity gradient changes may cause oversmoothing,resulting in significant measurement errors.To address this problem,the traditional particle tracking velocimetry method based on an optical flow was improved.The level set segmentation algorithm was used to obtain the boundary contour of the region with large velocity gradient changes,and the non-uniform flow field was divided into regions according to the boundary contour to obtain sub-regions with uniform velocity distribution.The particle tracking velocimetry method based on optical flow was used to measure the granular flow velocity in each sub-region,thus avoiding the problem of granular flow distribution.The simulation results show that the measurement accuracy of this method is approximately 10%higher than that of traditional methods.The method was applied to a velocity measurement experiment on dense granular flow in silos,and the velocity distribution of the granular flow was obtained,verifying the practicality of the method in granular flow fields.
基金financially supported by the National Key Research and Development Program of China(Grant No.2021YFA1600900)the National Natural Science Foundation of China(Grant Nos.U22A20174,52071207,51971137,11875192,and U1930101)the Natural Science Foundation of Shanghai(China,Grant No.22ZR1432800).
文摘Neutron shielding materials face imbalanced behaviors among shielding,strength,and ductility properties.Based on the requirement of the high property shielding particles,a superior semi-coherentτ(Al4 MgGd)phase was designed and predicted by cluster expansion(CE)method using density functional theory calculations.To realize its shielding property,the Powder Metallurgy-based routines(i.e.,powder fabrication,spark plasma sintering,and hot extrusion techniques)are used to fabricate 6TiB_(2)/Al-6Mg-5Gd(wt.%)composite with dispersed refinedτphases and homogenized TiB_(2) distribution.The atomic structure of ternary phase τ is examined by aberration-corrected high-angle annual dark-field(HAADF)scanning transmission electron microscope(STEM)and energy dispersive X-ray spectroscopy(EDXS)STEM experiments,which is well complied with the calculated compound(Al_(4)MgGd).In detail,theτ(Al_(4)MgGd)phase has a semi-coherent interface both with α-Al and TiB_(2),which is consistent with the prediction of interface relationships.With the optimized interfaces,the TiB_(2) and τ phases can effectively promote recrystallization and suppress grain growth,leading to the formation of ultra-fine grain structure.Then,the composite exhibits advanced shielding properties(Macroscopic transmission cross section ~24.1/cm,higher than 30%B_(4) C/Al)and optimized synergic mechanical properties(Ultimate tensile strength ~506 MPa,elongation ~12.9%),which are far higher than available Al-based neutron shielding materials.Finally,the underlying strength-ductility mechanisms are discussed.Critically,the design and optimization of shielding particle interfaces are reliable strategies for developing novel structural-functional integrated materials.
基金supported by the National Natural Science Foundation of China(Grant No.52201323).
文摘In this study,a common-node DEM-SPH coupling model based on the shared node method is proposed,and a fluid–structure coupling method using the common-node discrete element method-smoothed particle hydrodynamics(DS-SPH)method is developed using LS-DYNA software.The DEM and SPH are established on the same node to create common-node DEM-SPH particles,allowing for fluid–structure interactions.Numerical simulations of various scenarios,including water entry of a rigid sphere,dam-break propagation over wet beds,impact on an ice plate floating on water and ice accumulation on offshore structures,are conducted.The interaction between DS particles and SPH fluid and the crack generation mechanism and expansion characteristics of the ice plate under the interaction of structure and fluid are also studied.The results are compared with available data to verify the proposed coupling method.Notably,the simulation results demonstrated that controlling the cutoff pressure of internal SPH particles could effectively control particle splashing during ice crushing failure.
基金Project supported by the National Natural Science Foundation of China(No.52109068)the Water Conservancy Technology Project of Jiangsu Province of China(No.2022060)。
文摘Viscoelastic flows play an important role in numerous engineering fields,and the multiscale algorithms for simulating viscoelastic flows have received significant attention in order to deepen our understanding of the nonlinear dynamic behaviors of viscoelastic fluids.However,traditional grid-based multiscale methods are confined to simple viscoelastic flows with short relaxation time,and there is a lack of uniform multiscale scheme available for coupling different solvers in the simulations of viscoelastic fluids.In this paper,a universal multiscale method coupling an improved smoothed particle hydrodynamics(SPH)and multiscale universal interface(MUI)library is presented for viscoelastic flows.The proposed multiscale method builds on an improved SPH method and leverages the MUI library to facilitate the exchange of information among different solvers in the overlapping domain.We test the capability and flexibility of the presented multiscale method to deal with complex viscoelastic flows by solving different multiscale problems of viscoelastic flows.In the first example,the simulation of a viscoelastic Poiseuille flow is carried out by two coupled improved SPH methods with different spatial resolutions.The effects of exchanging different physical quantities on the numerical results in both the upper and lower domains are also investigated as well as the absolute errors in the overlapping domain.In the second example,the complex Wannier flow with different Weissenberg numbers is further simulated by two improved SPH methods and coupling the improved SPH method and the dissipative particle dynamics(DPD)method.The numerical results show that the physical quantities for viscoelastic flows obtained by the presented multiscale method are in consistence with those obtained by a single solver in the overlapping domain.Moreover,transferring different physical quantities has an important effect on the numerical results.
基金Project supported by the National Natural Science Foundation of China (No.10202018)
文摘An h-adaptivity analysis scheme based on multiple scale reproducing kernel particle method was proposed, and two node refinement strategies were constructed using searching-neighbor-nodes(SNN) and local-Delaunay-triangulation(LDT) tech-niques, which were suitable and effective for h-adaptivity analysis on 2-D problems with the regular or irregular distribution of the nodes. The results of multiresolution and h-adaptivity analyses on 2-D linear elastostatics and bending plate problems demonstrate that the improper high-gradient indicator will reduce the convergence property of the h-adaptivity analysis, and that the efficiency of the LDT node refinement strategy is better than SNN, and that the presented h-adaptivity analysis scheme is provided with the validity, stability and good convergence property.
基金This work was supported by the National Key R&D Program‘Transportation Infrastructure’project(No.2022YFB2603400).
文摘The compaction quality of subgrade filler strongly affects subgrade settlement.The main objective of this research is to analyze the macro-and micro-mechanical compaction characteristics of subgrade filler based on the real shape of coarse particles.First,an improved Viola-Jones algorithm is employed to establish a digitalized 2D particle database for coarse particle shape evaluation and discrete modeling purposes of subgrade filler.Shape indexes of 2D subgrade filler are then computed and statistically analyzed.Finally,numerical simulations are performed to quantitatively investigate the effects of the aspect ratio(AR)and interparticle friction coefficient(μ)on the macro-and micro-mechanical compaction characteristics of subgrade filler based on the discrete element method(DEM).The results show that with the increasing AR,the coarse particles are narrower,leading to the increasing movement of fine particles during compaction,which indicates that it is difficult for slender coarse particles to inhibit the migration of fine particles.Moreover,the average displacement of particles is strongly influenced by the AR,indicating that their occlusion under power relies on particle shapes.The dis-placement and velocity of fine particles are much greater than those of the coarse particles,which shows that compaction is primarily a migration of fine particles.Under the cyclic load,the interparticle friction coefficientμhas little effect on the internal structure of the sample;under the quasi-static loads,however,the increase inμwill lead to a significant increase in the porosity of the sample.This study could not only provide a novel approach to investigate the compaction mechanism but also establish a new theoretical basis for the evaluation of intelligent subgrade compaction.
文摘Hydrothermal method was used to synthesize nanoscale particles of MnZn ferrites. The crystallites were characterized by XRD, TEM and SEM. The effects of the reaction time, temperature and additives on the product were investigated. Crystallization process would be carried out above 160 ℃ for 5 h or more, higher temperature can reduce the reaction time. Additives were used to remove impurities such as Fe 2O 3, ZnMnO 3.10～15 nm pure slightly agglomerated MnZn ferrite crystallites with a narrow grain size distribution were obtained.
基金Project supported by the National Natural Science Foundation of China(Nos.91648101 and11672233)the Northwestern Polytechnical University(NPU)Foundation for Fundamental Research(No.3102017AX008)the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.S201710699033)
文摘Multibody system dynamics provides a strong tool for the estimation of dynamic performances and the optimization of multisystem robot design. It can be described with differential algebraic equations(DAEs). In this paper, a particle swarm optimization(PSO) method is introduced to solve and control a symplectic multibody system for the first time. It is first combined with the symplectic method to solve problems in uncontrolled and controlled robotic arm systems. It is shown that the results conserve the energy and keep the constraints of the chaotic motion, which demonstrates the efficiency, accuracy, and time-saving ability of the method. To make the system move along the pre-planned path, which is a functional extremum problem, a double-PSO-based instantaneous optimal control is introduced. Examples are performed to test the effectiveness of the double-PSO-based instantaneous optimal control. The results show that the method has high accuracy, a fast convergence speed, and a wide range of applications.All the above verify the immense potential applications of the PSO method in multibody system dynamics.
文摘An h-adaptivity analysis scheme based on multiple scale reproducing kernel particle method was proposed, and two node refinement strategies were constructed using searching-neighbor-nodes（SNN） and local-Delaunay-triangulation（LDT） techniques, which were suitable and effective for h-adaptivity analysis on 2-D problems with the regular or irregular distribution of the nodes. The results of multiresolution and h- adaptivity analyses on 2-D linear elastostatics and bending plate problems demonstrate that the improper high-gradient indicator will reduce the convergence property of the h- adaptivity analysis, and that the efficiency of the LDT node refinement strategy is better than SNN, and that the presented h-adaptivity analysis scheme is provided with the validity, stability and good convergence property.
