The intersection method is one of the basic approaches for locating earthquakes and is not only robust but also efficient. However, its location accuracy is not high, especially for focal depth because the velocity mo...The intersection method is one of the basic approaches for locating earthquakes and is not only robust but also efficient. However, its location accuracy is not high, especially for focal depth because the velocity model used for the conventional intersection method is based on homogeneous or laterally homogeneous media, which is too simple. In order to improve the accuracy, we have modified the existing intersection method. In the modified approach, the earthquake loci are not assumed to be circular or hyperbolic and calculation accuracy is improved using a minimum traveltime tree algorithm for tracing rays. The numerical model shows that the modified method can locate earthquakes in complex velocity models.展开更多
Acoupled biharmonic spline and linear interpolation algorithm was proposed to create a three-dimensional smooth deposit model with minimal curvature containing grade and position data. To obtain the optimal technical ...Acoupled biharmonic spline and linear interpolation algorithm was proposed to create a three-dimensional smooth deposit model with minimal curvature containing grade and position data. To obtain the optimal technical parameters, such as cuttingheight and drum diameter, a virtual longwall mining procedure was modelled by simulating the actual fully mechanized longwall mining process. Based on the above work, a bauxite deposit in a longwall mining panel was modelled by scattered grade data from ores sampled on the entry wall. The deposit was then demarcated by industrial indexes and sliced according to the virtual longwallmining procedure. The results show that the proposed interpolation algorithm can depict the stratiform structure of bauxite depositsand that the uncovered bauxite deposit has high proportions of high-grade and rich ore. The ranges of optimal cutting height and drum diameters are 1.72-2.84 m and 1.42-1.72 m, respectively. Finally, an intellectualized longwall mining procedure was designed to guide the mining process with the lowest dilution and loss rates.展开更多
A new predictive model for evaluating the vibration of a sawing machine was developed using a new rock classification system. The predictors are machine parameters and a rock sawability index. The new rock classificat...A new predictive model for evaluating the vibration of a sawing machine was developed using a new rock classification system. The predictors are machine parameters and a rock sawability index. The new rock classification system includes four major parameters of the rock: uniaxial compressive strength, abrasiv- ity index, mean MoWs hardness, and Young's modulus. The FAHP approach was used when determining the weights of these parameters by six decision makers. Two groups of carbonate rocks were sawn using a fully-instrumented laboratory sawing rig at different feed rates and depths of cut. During the sawing trials system vibration was monitored as a measure of saw performance. Then, a new statistical model was obtained by multiple regression on the machining parameters and the rock sawability index. The model is very useful for the evaluation of the system vibration, and for selecting suitable machining parameters, from a limited set of mechanical properties.展开更多
A lattice Boltzmann model is presented to simulate the deformation and motions of a red blood cell (RBC) in a shear flow. The curvatures of the membrane of a static RBC with different chemical potentiM drops calcula...A lattice Boltzmann model is presented to simulate the deformation and motions of a red blood cell (RBC) in a shear flow. The curvatures of the membrane of a static RBC with different chemical potentiM drops calculated by our model agree with those computed by a shooting method very well. Our simulation results show that in a shear flow, biconcave RBC becomes highly flattened and undergoes tank-treading motion. With intrinsically parallel dynamics, this lattice Boltzmann method is expected to find wide applications to both single and multi-vesicles suspension as well as complex open membranes in various fluid flows for a wide range of Reynolds numbers.展开更多
The behavior of single bubble rising in quiescent shear-thinning tlmds was lnvestlgateO numerically by level set metnoa. number of bubbles in a large range of Reynolds number and Eotvos number were investigated includ...The behavior of single bubble rising in quiescent shear-thinning tlmds was lnvestlgateO numerically by level set metnoa. number of bubbles in a large range of Reynolds number and Eotvos number were investigated including spherical, oblate and spherical. The bubble shape and drag coefficient were compared with experimental results. It is observed that the simulated results show good conformity to experimental results over a wide range of Reynolds number. In addition, the detailed flow field based on the reference coordinate system moving with the bubble is obtained, and the relationship among flow field, bubble shape and velocity is discussed.展开更多
Metal matrix composites reinforced with graphite particles provide better machinability and tribological properties. The present study attempts to find the optimal level of machining parameters for multi-performance c...Metal matrix composites reinforced with graphite particles provide better machinability and tribological properties. The present study attempts to find the optimal level of machining parameters for multi-performance characteristics in turning of Al-SiC-Gr hybrid composites using grey-fuzzy algorithm. The hybrid composites with 5%, 7.5% and 10% combined equal mass fraction of SiC-Gr particles were used for the study and their corresponding tensile strength values are 170, 210, 204 MPa respectively. Al-10%(SiC-Gr) hybrid composite provides better machinability when compared with composites with 5% and 7.5% of SiC-Gr. Grey-fuzzy logic approach offers improved grey-fuzzy reasoning grade and has less uncertainties in the output when compared with grey relational technique. The confirmatory test reveals an increase in grey-fuzzy reasoning grade from 0.619 to 0.891, which substantiates the improvement in multi-performance characteristics at the optimal level of process parameters setting.展开更多
In this unified model,we introduce the electron-phonon coupling time(tie) and laser pulse width(tp).For long pulses,it can substitute for the traditional thermal conduction model;while for ultrashort pulses,it can sub...In this unified model,we introduce the electron-phonon coupling time(tie) and laser pulse width(tp).For long pulses,it can substitute for the traditional thermal conduction model;while for ultrashort pulses,it can substitute for the standard two-temperature model.As an example of the gold target,we get the dependence of the electron and ion temperature evolvement on the time and position by solving the thermal conduction equation using the finite-difference time-domain(FDTD) method.It is in good agreement with experimental data.We obtain the critical temperature of the onset of ablation using the Saha equation and then obtain the theoretical value of the laser ablation threshold when the laser pulse width ranges from nano-second to femtosecond timescale,which consists well with the experimental data.展开更多
To address large scale industrial processes,a novel Lagrangian scheme is proposed to decompose a refinery scheduling problem with operational transitions in mode switching into a production subproblem and a blending a...To address large scale industrial processes,a novel Lagrangian scheme is proposed to decompose a refinery scheduling problem with operational transitions in mode switching into a production subproblem and a blending and delivery subproblem.To accelerate the convergence of Lagrange multipliers,some auxiliary constraints are added in the blending and delivery subproblem.A speed-up scheme is presented to increase the efficiency for solving the production subproblem.An initialization scheme of Lagrange multipliers and a heuristic algorithm to find feasible solutions are designed.Computational results on three cases with different lengths of time horizons and different numbers of orders show that the proposed Lagrangian scheme is effective and efficient.展开更多
It is of significance to research failure mechanism of debris landslides that are widespread in the Three Gorges Reservoir Area. Based on the statistical analysis of the developmental law and failure mode of debris la...It is of significance to research failure mechanism of debris landslides that are widespread in the Three Gorges Reservoir Area. Based on the statistical analysis of the developmental law and failure mode of debris landslides in the Three Gorges Reservoir, the mode of progressive failure is found. The mechanical model for progressive failure of debris landslides with two slip bands is also established by applying slice method. According to the results of the downslide force between adjacent slices, if the downslide force of lower slice is larger than zero, the slice fails along the major sliding surface, otherwise it is stable. In result, the failure range is obtained. The stress function can be determined through dimensional analysis of failure slice. According to static boundary conditions of the slice, stress state of any point in the slice can be obtained. Then stress state of any point in the secondary slip band can also be established. The failure of the secondary slip band is judged on the basis of Mohr-Coulomb failure criterion. Therefore, a mechanical method is proposed to analyze the progressive failure of debris landslide with two slip bands.展开更多
Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the st...Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the stress is linearly dependent on the strain and the damage modes of specimens are brittle fracture for both kinds of tests. Dispersibility models of compression and shear strength are expressed as Re-N(415.39, 6 586.36) and Rs-ln(5.071 8, 0.155 3), respectively. When normal and lognormal distributions were used to describe the dispersibility models of compression and shear strength, and the compression or shear load follows the normal distribution, the almost same failure probability can be obtained from different reliability analysis methods.展开更多
In order to study the failure process of an anchorage structure and the evolution law of the body's defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods (DSCM). T...In order to study the failure process of an anchorage structure and the evolution law of the body's defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods (DSCM). The stress distribution of the anchorage interface was investigated using the particle flow numerical simulation method. The results indicate that there are three stages in the deformation and fail- ure process of an anchorage structure: elastic bonding stage, a de-bonding stage and a failure stage. The stress distribution in the interface controls the stability of the structure. In the elastic bonding stage, the shear stress peak point of the interface is close to the loading end, and the displacement field gradually develops into a "V" shape, in the de-bonding stage, there is a shear stress plateau in the center of the anchorage section, and shear strain localization begins to form in the deformation field. In the failure stage, the bonding of the interface fails rapidly and the shear stress peak point moves to the anchorage free end. The anchorage structure moves integrally along the macro-cracl~ The de-bonding stage is a research focus in the deformation and failure process of an anchorage structure, and plays an important guiding role in roadway support design and prediction of the stability of the surrounding rock.展开更多
In the last decade,3D printing,especially fused deposition modeling(FDM),has revolutionized manufacturing with intricate designs.Traditional 3-axis FDM printers face challenges with complex geometries,but 5-axis versi...In the last decade,3D printing,especially fused deposition modeling(FDM),has revolutionized manufacturing with intricate designs.Traditional 3-axis FDM printers face challenges with complex geometries,but 5-axis versions offer more design freedom.However,it requires specialized strategies.This research presents a model for 5-axis FDM printers using Bézier curves with an algorithm to enhance print quality.The result shows significant accuracy improvements,especially for curve-based tasks.In addition,this study deepens the understanding of 5-axis FDM technology,setting a solid basis for further research and potentially refining manufacturing methods.展开更多
A Cartesian grid generation method is developed in this study.Two kinds of solid modeling methods,CSG and STL models,are used for complicated solid modeling.The staircase boundary approximation is implemented to handl...A Cartesian grid generation method is developed in this study.Two kinds of solid modeling methods,CSG and STL models,are used for complicated solid modeling.The staircase boundary approximation is implemented to handle irregular geometries and the computational domain is discretized using a regular Cartesian grid.Using the edge-based integral slice algorithm,the models are sliced with a set of parallel planes to generate 2D slices information.The scan line filling technique is used to achieve grid generation after slicing.Two grid generation examples with a CSG model and a STL model are given to test the capability of the grid generation method.For grid displaying,a method is proposed to remove the hidden surfaces fasten based on the topology of orthogonal hexahedral grids.The parallelization of grid displaying is achieved by employing multi-threaded parallel technique.Parallel test results show that the parallel algorithm has the absolute advantage on speed compared to the serial algorithm.展开更多
Normally large amounts of particles are required to accurately simulate the metal cutting process,which consumes a lot of computing time and storage.Adaptive techniques can help decrease the number of particles,hence ...Normally large amounts of particles are required to accurately simulate the metal cutting process,which consumes a lot of computing time and storage.Adaptive techniques can help decrease the number of particles,hence reducing the runtime.This paper presents a novel adaptive smoothed particle hydrodynamics(SPH)method for the metal cutting simulation.The spatial resolution changes adaptively according to the distance to the tool tip by the particle splitting and merging.More particles are selected in the region where the workpiece and the tool are in contact.Since the contact region constantly changes during the cutting process,two quadrilateral frames are adopted in the adaptive algorithm to dynamically change the distribution of particles.One frame for the refinement,the other for the coarsening.These frames move at the same speed as the tool.To test the computational efficiency,the metal cutting process is simulated by using SPH with three different adaptive approaches.Numerical results show that the proposed adaptive algorithm with dynamic refinement and coarsening can significantly optimize the runtime.展开更多
This paper presents a novel numerical model using a fully three-dimensional(3D),incompressible,two-phase flow NavierStokes(NS)solver,which are discretized by the finite volume method.A high-resolution STACS-VOF method...This paper presents a novel numerical model using a fully three-dimensional(3D),incompressible,two-phase flow NavierStokes(NS)solver,which are discretized by the finite volume method.A high-resolution STACS-VOF method is used to capture the interface between the air and water phases.The validity of the simulation following this model is examined through3D shear flow and collapsing cylinder of water.Then,this proposed model is adopted to simulate the dynamics of flow involved with surge bore propagating over a slope in the swash zone.The computed uprush shoreline motion and the tip of runup water surface agreed well with experimental data,which indicates that this model can describe the aerated flow accurately.Numerical analyses are also applied to the spatial and temporal distributions of free-surface,instantaneous flow field,and maximal bed shear stress in the bore collapse,uprush and backwash processes.The results from the analyses reveal that the flow dynamics is complicated after the bore breaks,and the proposed model can well capture the structure characteristics of sheet flow,which are better than the previous results.All these findings are of help to understand the pattern of sediment transport and coastal evolution in the swash zone.展开更多
Design and application of tunable phononic crystals(PnCs)are attracting increasing interest due to their promising capabilities to manipulate acoustic and elastic waves effectively.This paper investigates topology opt...Design and application of tunable phononic crystals(PnCs)are attracting increasing interest due to their promising capabilities to manipulate acoustic and elastic waves effectively.This paper investigates topology optimization of the magnetorheological(MR)materials including PnCs for opening the tunable and wide bandgaps.Therein,the bandgap tunability of the PnCs is achieved by shear modulus variation of MR materials under a continuously changing applied magnetic field.The pseudo elemental densities representing the bi-material distribution inside the PnC unit cell are taken as design variables and interpolated with an artificial MR penalization model.An aggregated bandgap index for enveloping the extreme values ofbandgap width and tunable range of the MR included smart PnCs is proposed as the objective function.In this context,the sensitivity analysis scheme is derived,and the optimization problem is solved with the gradient-based mathematical programming method.The effectiveness of the proposed optimization method is demonstrated by numerical examples,where the optimized solutions present tunable and stably wide bandgap characteristics under different magnetic fields.The tunable optimized PnCs based device that can provide a wider tunable bandgap range is also explored.展开更多
基金This work is supported by the National Natural Science Foundation of China(40674044)the Special Foundation for Basic Professional Scientific Research (DQJB06A02)
文摘The intersection method is one of the basic approaches for locating earthquakes and is not only robust but also efficient. However, its location accuracy is not high, especially for focal depth because the velocity model used for the conventional intersection method is based on homogeneous or laterally homogeneous media, which is too simple. In order to improve the accuracy, we have modified the existing intersection method. In the modified approach, the earthquake loci are not assumed to be circular or hyperbolic and calculation accuracy is improved using a minimum traveltime tree algorithm for tracing rays. The numerical model shows that the modified method can locate earthquakes in complex velocity models.
基金Project(11472311)supported by the National Natural Science Foundation of ChinaProject(2015CX005)supported by the Innovation Driven Plan of Central South University of ChinaProject(2015zzts083)supported by the Fundamental Research Funds for the Central Universities of Central South University,China
文摘Acoupled biharmonic spline and linear interpolation algorithm was proposed to create a three-dimensional smooth deposit model with minimal curvature containing grade and position data. To obtain the optimal technical parameters, such as cuttingheight and drum diameter, a virtual longwall mining procedure was modelled by simulating the actual fully mechanized longwall mining process. Based on the above work, a bauxite deposit in a longwall mining panel was modelled by scattered grade data from ores sampled on the entry wall. The deposit was then demarcated by industrial indexes and sliced according to the virtual longwallmining procedure. The results show that the proposed interpolation algorithm can depict the stratiform structure of bauxite depositsand that the uncovered bauxite deposit has high proportions of high-grade and rich ore. The ranges of optimal cutting height and drum diameters are 1.72-2.84 m and 1.42-1.72 m, respectively. Finally, an intellectualized longwall mining procedure was designed to guide the mining process with the lowest dilution and loss rates.
文摘A new predictive model for evaluating the vibration of a sawing machine was developed using a new rock classification system. The predictors are machine parameters and a rock sawability index. The new rock classification system includes four major parameters of the rock: uniaxial compressive strength, abrasiv- ity index, mean MoWs hardness, and Young's modulus. The FAHP approach was used when determining the weights of these parameters by six decision makers. Two groups of carbonate rocks were sawn using a fully-instrumented laboratory sawing rig at different feed rates and depths of cut. During the sawing trials system vibration was monitored as a measure of saw performance. Then, a new statistical model was obtained by multiple regression on the machining parameters and the rock sawability index. The model is very useful for the evaluation of the system vibration, and for selecting suitable machining parameters, from a limited set of mechanical properties.
基金supported by National Natural Science Foundation of China under Grant No. 10747004the Guangxi Science Foundation under Grant Nos. 0640064 and 0542045
文摘A lattice Boltzmann model is presented to simulate the deformation and motions of a red blood cell (RBC) in a shear flow. The curvatures of the membrane of a static RBC with different chemical potentiM drops calculated by our model agree with those computed by a shooting method very well. Our simulation results show that in a shear flow, biconcave RBC becomes highly flattened and undergoes tank-treading motion. With intrinsically parallel dynamics, this lattice Boltzmann method is expected to find wide applications to both single and multi-vesicles suspension as well as complex open membranes in various fluid flows for a wide range of Reynolds numbers.
基金Project(21406141)supported by the National Natural Science Foundation of ChinaProject(20141078)supported by the Scientific Research Starting Foundation for Doctors of Liaoning Province,China+1 种基金Project(L2014060)supported by the Foundation of Department of Education of Liaoning Province,ChinaProject(157B21)supported by the Scientific Research Starting Foundation for Doctors of Shenyang Aerospace University,China
文摘The behavior of single bubble rising in quiescent shear-thinning tlmds was lnvestlgateO numerically by level set metnoa. number of bubbles in a large range of Reynolds number and Eotvos number were investigated including spherical, oblate and spherical. The bubble shape and drag coefficient were compared with experimental results. It is observed that the simulated results show good conformity to experimental results over a wide range of Reynolds number. In addition, the detailed flow field based on the reference coordinate system moving with the bubble is obtained, and the relationship among flow field, bubble shape and velocity is discussed.
文摘Metal matrix composites reinforced with graphite particles provide better machinability and tribological properties. The present study attempts to find the optimal level of machining parameters for multi-performance characteristics in turning of Al-SiC-Gr hybrid composites using grey-fuzzy algorithm. The hybrid composites with 5%, 7.5% and 10% combined equal mass fraction of SiC-Gr particles were used for the study and their corresponding tensile strength values are 170, 210, 204 MPa respectively. Al-10%(SiC-Gr) hybrid composite provides better machinability when compared with composites with 5% and 7.5% of SiC-Gr. Grey-fuzzy logic approach offers improved grey-fuzzy reasoning grade and has less uncertainties in the output when compared with grey relational technique. The confirmatory test reveals an increase in grey-fuzzy reasoning grade from 0.619 to 0.891, which substantiates the improvement in multi-performance characteristics at the optimal level of process parameters setting.
文摘In this unified model,we introduce the electron-phonon coupling time(tie) and laser pulse width(tp).For long pulses,it can substitute for the traditional thermal conduction model;while for ultrashort pulses,it can substitute for the standard two-temperature model.As an example of the gold target,we get the dependence of the electron and ion temperature evolvement on the time and position by solving the thermal conduction equation using the finite-difference time-domain(FDTD) method.It is in good agreement with experimental data.We obtain the critical temperature of the onset of ablation using the Saha equation and then obtain the theoretical value of the laser ablation threshold when the laser pulse width ranges from nano-second to femtosecond timescale,which consists well with the experimental data.
基金Supported by the National Natural Science Foundation of China(61273039,21276137)the National Science Fund for Distinguished Young Scholars of China(61525304)
文摘To address large scale industrial processes,a novel Lagrangian scheme is proposed to decompose a refinery scheduling problem with operational transitions in mode switching into a production subproblem and a blending and delivery subproblem.To accelerate the convergence of Lagrange multipliers,some auxiliary constraints are added in the blending and delivery subproblem.A speed-up scheme is presented to increase the efficiency for solving the production subproblem.An initialization scheme of Lagrange multipliers and a heuristic algorithm to find feasible solutions are designed.Computational results on three cases with different lengths of time horizons and different numbers of orders show that the proposed Lagrangian scheme is effective and efficient.
基金financially by National Natural Science Foundation Project "Shore Landslide and Risk Prediction of Secondary Surge Hazard in the Three Gorges Reservoir"(Grant No. 40872176)
文摘It is of significance to research failure mechanism of debris landslides that are widespread in the Three Gorges Reservoir Area. Based on the statistical analysis of the developmental law and failure mode of debris landslides in the Three Gorges Reservoir, the mode of progressive failure is found. The mechanical model for progressive failure of debris landslides with two slip bands is also established by applying slice method. According to the results of the downslide force between adjacent slices, if the downslide force of lower slice is larger than zero, the slice fails along the major sliding surface, otherwise it is stable. In result, the failure range is obtained. The stress function can be determined through dimensional analysis of failure slice. According to static boundary conditions of the slice, stress state of any point in the slice can be obtained. Then stress state of any point in the secondary slip band can also be established. The failure of the secondary slip band is judged on the basis of Mohr-Coulomb failure criterion. Therefore, a mechanical method is proposed to analyze the progressive failure of debris landslide with two slip bands.
基金Project(51175424) supported by the National Natural Science FoundationProject(B07050) supported by the 111 Project,ChinaProject (JC20110257) supported by the Basic Research Foundation of Northwestern Polytechnical University
文摘Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the stress is linearly dependent on the strain and the damage modes of specimens are brittle fracture for both kinds of tests. Dispersibility models of compression and shear strength are expressed as Re-N(415.39, 6 586.36) and Rs-ln(5.071 8, 0.155 3), respectively. When normal and lognormal distributions were used to describe the dispersibility models of compression and shear strength, and the compression or shear load follows the normal distribution, the almost same failure probability can be obtained from different reliability analysis methods.
基金financially supported by the National Key Basic Research Program of China (No.2010CB226805)the National Natural Science Foundation of China (Nos.51474136 and 51474013)+1 种基金the Opening Project Fund of State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology (No.MDPC2013KF06)the Research Award Fund for the Excellent Youth of Shandong University of Science and Technology (No.2011KYJQ106)
文摘In order to study the failure process of an anchorage structure and the evolution law of the body's defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods (DSCM). The stress distribution of the anchorage interface was investigated using the particle flow numerical simulation method. The results indicate that there are three stages in the deformation and fail- ure process of an anchorage structure: elastic bonding stage, a de-bonding stage and a failure stage. The stress distribution in the interface controls the stability of the structure. In the elastic bonding stage, the shear stress peak point of the interface is close to the loading end, and the displacement field gradually develops into a "V" shape, in the de-bonding stage, there is a shear stress plateau in the center of the anchorage section, and shear strain localization begins to form in the deformation field. In the failure stage, the bonding of the interface fails rapidly and the shear stress peak point moves to the anchorage free end. The anchorage structure moves integrally along the macro-cracl~ The de-bonding stage is a research focus in the deformation and failure process of an anchorage structure, and plays an important guiding role in roadway support design and prediction of the stability of the surrounding rock.
基金supported by the Na-tional Natural Science Foundation of China(Nos.51575266,52075258)。
文摘In the last decade,3D printing,especially fused deposition modeling(FDM),has revolutionized manufacturing with intricate designs.Traditional 3-axis FDM printers face challenges with complex geometries,but 5-axis versions offer more design freedom.However,it requires specialized strategies.This research presents a model for 5-axis FDM printers using Bézier curves with an algorithm to enhance print quality.The result shows significant accuracy improvements,especially for curve-based tasks.In addition,this study deepens the understanding of 5-axis FDM technology,setting a solid basis for further research and potentially refining manufacturing methods.
基金supported by the National Basic Research Program of China(Grant No.2010CB832706)the National Natural Science Foundation of China(Grant No.11172041)the Project of State Key Laboratory of Explosion Science and Technology(Grant No.YBKT14-03)
文摘A Cartesian grid generation method is developed in this study.Two kinds of solid modeling methods,CSG and STL models,are used for complicated solid modeling.The staircase boundary approximation is implemented to handle irregular geometries and the computational domain is discretized using a regular Cartesian grid.Using the edge-based integral slice algorithm,the models are sliced with a set of parallel planes to generate 2D slices information.The scan line filling technique is used to achieve grid generation after slicing.Two grid generation examples with a CSG model and a STL model are given to test the capability of the grid generation method.For grid displaying,a method is proposed to remove the hidden surfaces fasten based on the topology of orthogonal hexahedral grids.The parallelization of grid displaying is achieved by employing multi-threaded parallel technique.Parallel test results show that the parallel algorithm has the absolute advantage on speed compared to the serial algorithm.
基金the National Natural Science Foundation of China(Grant Nos.12002290 and 11772274).
文摘Normally large amounts of particles are required to accurately simulate the metal cutting process,which consumes a lot of computing time and storage.Adaptive techniques can help decrease the number of particles,hence reducing the runtime.This paper presents a novel adaptive smoothed particle hydrodynamics(SPH)method for the metal cutting simulation.The spatial resolution changes adaptively according to the distance to the tool tip by the particle splitting and merging.More particles are selected in the region where the workpiece and the tool are in contact.Since the contact region constantly changes during the cutting process,two quadrilateral frames are adopted in the adaptive algorithm to dynamically change the distribution of particles.One frame for the refinement,the other for the coarsening.These frames move at the same speed as the tool.To test the computational efficiency,the metal cutting process is simulated by using SPH with three different adaptive approaches.Numerical results show that the proposed adaptive algorithm with dynamic refinement and coarsening can significantly optimize the runtime.
基金supported by the National Natural Science Foundation of China(Grant Nos.51239001,51179015,41176072)
文摘This paper presents a novel numerical model using a fully three-dimensional(3D),incompressible,two-phase flow NavierStokes(NS)solver,which are discretized by the finite volume method.A high-resolution STACS-VOF method is used to capture the interface between the air and water phases.The validity of the simulation following this model is examined through3D shear flow and collapsing cylinder of water.Then,this proposed model is adopted to simulate the dynamics of flow involved with surge bore propagating over a slope in the swash zone.The computed uprush shoreline motion and the tip of runup water surface agreed well with experimental data,which indicates that this model can describe the aerated flow accurately.Numerical analyses are also applied to the spatial and temporal distributions of free-surface,instantaneous flow field,and maximal bed shear stress in the bore collapse,uprush and backwash processes.The results from the analyses reveal that the flow dynamics is complicated after the bore breaks,and the proposed model can well capture the structure characteristics of sheet flow,which are better than the previous results.All these findings are of help to understand the pattern of sediment transport and coastal evolution in the swash zone.
基金supported by the National Natural Science Foundation of China(Grant No.12102079).
文摘Design and application of tunable phononic crystals(PnCs)are attracting increasing interest due to their promising capabilities to manipulate acoustic and elastic waves effectively.This paper investigates topology optimization of the magnetorheological(MR)materials including PnCs for opening the tunable and wide bandgaps.Therein,the bandgap tunability of the PnCs is achieved by shear modulus variation of MR materials under a continuously changing applied magnetic field.The pseudo elemental densities representing the bi-material distribution inside the PnC unit cell are taken as design variables and interpolated with an artificial MR penalization model.An aggregated bandgap index for enveloping the extreme values ofbandgap width and tunable range of the MR included smart PnCs is proposed as the objective function.In this context,the sensitivity analysis scheme is derived,and the optimization problem is solved with the gradient-based mathematical programming method.The effectiveness of the proposed optimization method is demonstrated by numerical examples,where the optimized solutions present tunable and stably wide bandgap characteristics under different magnetic fields.The tunable optimized PnCs based device that can provide a wider tunable bandgap range is also explored.