The hose-drogue system is a common method for soft aerial refueling,whereby the refueling tanker tows the drogue through the hose.In this paper,a mathematical-physical model of the hose-drogue system is developed and ...The hose-drogue system is a common method for soft aerial refueling,whereby the refueling tanker tows the drogue through the hose.In this paper,a mathematical-physical model of the hose-drogue system is developed and simulated using the Absolute Nodal Coordinate Formulation(ANCF)finite element method.A numerical solution program based on ANCF and ALE(Arbitrary Eulerian-Lagrange)-ANCF method was developed to simulate and analyze the horizontal and elongation release processes of the hose-drogue system at different towing points(underneath the wing and the belly of the aircraft).This program was developed by introducing an ALE description.The numerical solution program,developed based on the ANCF and ALE-ANCF methods,represents a significant advancement in computational efficiency for the rigid-flexible coupled multibody system of the air refueling hose-drogue system.This program can provide a valuable reference for the qualitative design of the hose-drogue multibody system in soft air refueling,while maintaining the necessary accuracy.展开更多
Solidifi cation shrinkage has been recognized as an important factor for macrosegregation formation. An arbitrary Lagrangian–Eulerian(ALE) model is constructed to predict the macrosegregation caused by thermal–solut...Solidifi cation shrinkage has been recognized as an important factor for macrosegregation formation. An arbitrary Lagrangian–Eulerian(ALE) model is constructed to predict the macrosegregation caused by thermal–solutal convection and solidi-fi cation shrinkage. A novel mesh update algorithm is developed to account for the domain change induced by solidifi cation shrinkage. The velocity–pressure coupling between the non-homogenous mass conservation equation and momentum equation is addressed by a modifi ed pressure correction method. The governing equations are solved by the streamline-upwind/Petrov–Galerkin-stabilized fi nite element algorithm. The application of the model to the Pb-19.2 wt%Sn alloy solidifi cation problem is considered. The inverse segregation is successfully predicted, and reasonable agreement with the literature results is obtained. Thus, the ALE model is established to be a highly effective tool for predicting the macrosegregation caused by solidifi cation shrinkage and thermal–solutal convection. Finally, the effect of solidifi cation shrinkage is analyzed. The results demonstrate that solidifi cation shrinkage delays the advance of the solidifi cation front and intensifi es the segregation.展开更多
A two-dimensional finite element(FE)model for the high speed turning operations when orthogonally machining AISI H13 tool steel at 49HRC using poly crystalline cubic boron nitride(PCBN)is described.An arbitrary Lagran...A two-dimensional finite element(FE)model for the high speed turning operations when orthogonally machining AISI H13 tool steel at 49HRC using poly crystalline cubic boron nitride(PCBN)is described.An arbitrary Lagrangian Eulerian(ALE)method has been adopted which does not need any chip separation criteria as opposed to the traditional Lagrangian approach.Through FE simulations temperature and stresses distributions are presented that could be helpful in predicting tool life and improving process parameters.The results show that high temperatures are generated along the tool rake face as compared to the shear zone temperatures due to high thermal conductivity of PCBN tools.展开更多
The study of cylindrically symmetric compressible fluid is interesting from both theoretical and numerical points of view. In this paper, the typical spherical sym- metry properties of the numerical schemes are discus...The study of cylindrically symmetric compressible fluid is interesting from both theoretical and numerical points of view. In this paper, the typical spherical sym- metry properties of the numerical schemes are discussed, and an area weighted scheme is extended from a Lagrangian method to an arbitrary Lagrangian and Eulerian （ALE） method. Numerical results are presented to compare three discrete configurations, i.e., the control volume scheme, the area weighted scheme, and the plane scheme with the addition of a geometrical source. The fact that the singularity arises from the geometri- cal source term in the plane scheme is illustrated. A suggestion for choosing the discrete formulation is given when the strong shock wave problems are simulated.展开更多
A computational procedure is developed to solve the problems of coupled motion of a structure and a viscous incompressible fluid. In order to incorporate the effect of the moving surface of the structure as well as th...A computational procedure is developed to solve the problems of coupled motion of a structure and a viscous incompressible fluid. In order to incorporate the effect of the moving surface of the structure as well as the free surface motion, the arbitrary Lagrangian-Eulerian formulation is employed as the basis of the finite element spatial discretization. For numerical integration in time, the fraction,step method is used. This method is useful because one can use the same linear interpolation function for both velocity and pressure. The method is applied to the nonlinear interaction of a structure and a tuned liquid damper. All computations are performed with a personal computer.展开更多
Sloshing has a widespread application in many industries including automotive, aerospace, ship building and motorcycle manufacturing. The goals of sloshing simulation is to first study the sloshing pattern and then im...Sloshing has a widespread application in many industries including automotive, aerospace, ship building and motorcycle manufacturing. The goals of sloshing simulation is to first study the sloshing pattern and then improve the tank design to reduce noise levels, stresses on the structure and optimize the baffle arrangements. In this project simulation of the fluid in tank is studied and the design modification with baffle plate is considered to minimize the sloshing phenomena using Arbitrary Langrangian Eulerian （ALE） method. Also it is explained that there is need to analyze the sloshing phenomena in detail. Arbitrary Langrangian Eulerian finite element methods gain interest for the capability to control mesh geometry independently from material geometry, the ALE methods are used to create a new undistorted mesh for the fluid domain. In this paper we use the ALE technique to solve fuel slosh problem. Fuel slosh is an important design consideration not only for the fuel tank, but also for the structure supporting the fuel tank. Fuel slosh can be generated by many ways： abrupt changes in acceleration （braking）, as well as abrupt changes in direction （highway exit-ramp）. Repetitive motion can also be involved if a sloshing resonance is generated. These sloshing events can in turn affect the overall performance 0fthe parent structure. A finite element analysis method has been developed to analyze this complex event. A new ALE formulation for the fluid mesh can be used to keep the fluid mesh integrity during the motion of the tank. This paper explains the analysis capabilities on a technical level.展开更多
The arbitrary Lagrangian-Eulerian（ALE） adaptive remeshing technology and the HyperXtrude software of transient finite element simulations were used on analogue simulation of aluminium extrusion processing.The field ...The arbitrary Lagrangian-Eulerian（ALE） adaptive remeshing technology and the HyperXtrude software of transient finite element simulations were used on analogue simulation of aluminium extrusion processing.The field distributions of strain rate,stress,temperature and velocity of metal flow were obtained.The results are basically consistent with the experiment,which indicates that this method may successfully predict the defects in the actual extrusion process.展开更多
The dynamic response performance of a large,cylindrical,fluid-filled steel container under high-speed impact is evaluated through fluid-structure interaction analysis using arbitrary Lagrange-Eulerian(ALE)method.The A...The dynamic response performance of a large,cylindrical,fluid-filled steel container under high-speed impact is evaluated through fluid-structure interaction analysis using arbitrary Lagrange-Eulerian(ALE)method.The ALE method is adopted to accurately calculate the structural behavior induced by the internal liquid impact of the container.The stress and strain results obtained from the finite element analysis are in line with the experimental shell impact data.The influences of drop angle,drop height,and flow impact frequency are discussed.Calculation results indicate that the impact stress and damage of the container increase with drop height.However,the amplitude of the oscillation and the impact stress increase when the container and flow impact resonance occur at a certain drop height.The impact stress shows a nonlinear relationship with drop angle.展开更多
The fluid-structure interaction (FSI) between the canopy and flow field on the inflating and inflated conditions is investigated based on the arbitrary Lagrange-Euler (ALE) method,in both a single-and double-cruciform...The fluid-structure interaction (FSI) between the canopy and flow field on the inflating and inflated conditions is investigated based on the arbitrary Lagrange-Euler (ALE) method,in both a single-and double-cruciform parachute systems.The projection area of canopy is calculated in the inflation process.The flow field characteristics and the interaction between canopies are analyzed.Results showed that,with free stream velocity of 50m/s,overinflation phenomenon would not occur during the inflation process of the double-cruciform-parachute system,because the collision and extrusion of the two canopies during inflation obstructed the oscillation of the inner gores.Concurrently,compared with the single-cruciform parachute,the vortex motion in the wake of double-cruciform-parachute is more intense.Thus the double-cruciform parachute system oscillated at a velocity of 50 m/s with an angle of less than 6.8°.By comparison,the oscillation angle of the single-cruciform parachute was within 3.5° at the velocity of 50m/s.The results are consistent with those of the wind tunnel test.展开更多
A computational fluid dynamics （CFD） simulation method based on 3-D Navier Stokes equation and Arbitrary Lagrangian Eulerian （ALE） method is presented to analyze the grooved slip- per performance of piston pump. T...A computational fluid dynamics （CFD） simulation method based on 3-D Navier Stokes equation and Arbitrary Lagrangian Eulerian （ALE） method is presented to analyze the grooved slip- per performance of piston pump. The moving domain of grooved slipper is transformed into a fixed reference domain by the ALE method, which makes it convenient to take the effects of rotate speed, body force, temperature, and oil viscosity into account. A geometric model to express the complex structure, which covers the orifice of piston and slipper, vented groove and the oil film, is constructed. Corresponding to different oil film thicknesses calculated in light of hydrostatic equilibrium theory and boundary conditions, a set of simulations is conducted in COMSOL to analyze the pump characteristics and effects of geometry （groove width and radius, orifice size） on these characteristics. Furthermore, the mechanics and hydraulics analyses are employed to validate the CFD model, and there is an excellent agreement between simulation and analytical results. The simulation results show that the sealing land radius, orifice size and groove width all dramatically affect the slipper behavior, and an optimum tradeoff among these factors is conducive to optimizing the pump design.展开更多
Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerica...Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.展开更多
An effective computational method is developed for dynamic analysis offluid-structure interaction problems involving large-amplitude sloshing of the fluid andlarge-displacement motion of the structure. The structure i...An effective computational method is developed for dynamic analysis offluid-structure interaction problems involving large-amplitude sloshing of the fluid andlarge-displacement motion of the structure. The structure is modeled as a rigid container supportedby a system consisting of springs and dashpots. The motion of the fluid is decomposed into twoparts: the large-displacement motion with the container and the large-amplitude sloshing relative tothe container. The former is conveniently dealt with by defining a container-fixed noninertiallocal frame, while the latter is easily handled by adopting an ALE kinematical description. Thisleads to an easy and accurate treatment of both the fluid-structure interface and the fluid freesurface without producing excessive distortion of the computational mesh. The coupling between thefluid and the structure is accomplished through the coupling matrices that can be easilyestablished. Two numerical examples, including a TLD-structure system and a simplified liquid-loadedvehicle system, are presented to demonstrate the effectiveness and reliability of the proposedmethod. The present work can also be applied to simulate fluid-structure problems incorporatingmultibody systems and several fluid domains.展开更多
Contaminated surfaces of the feedstock materials in aluminum alloy casting processes often produce various types of defects which can affect the tensile properties of the final products as well as their fatigue reliab...Contaminated surfaces of the feedstock materials in aluminum alloy casting processes often produce various types of defects which can affect the tensile properties of the final products as well as their fatigue reliabilities.Semi-solid processing takes advantage of a much higher apparent viscosity of the die cast materials by limiting the risk of oxides formed at the free surfaces to become incorporated into the casting when the material is injected into the die.Most of existing semi-solid processes that use billets as feedstock material are however tied up with a different type of contaminated surface.During the injection phase,the external-skin on the periphery of the billet,which has been in contact with air and lubricant during the transfer in the shot sleeve,can be incorporated into the casting.When subjected to a heat treatment,the lubricant is decomposed and produces lens shape porosities.This might be a cause of reject for most structural parts.To avoid this kind of defects,the paths along which the billet skin evolves must be controlled during filling.In order to investigate the possibility of skin inclusion into cast parts during injection of the billet,a two-phase finite element mixture model is employed to model the metal flow.The formation of a skin on the periphery of the billet is modeled by setting an initial solid phase concentration profile in the radial direction.Microscopic observations of the real castings show that the approach is able to model the shear layers and to predict the paths along which the"lens porosity"defects could be formed.An Arbitrary Eulerian-Lagangian(ALE) method is also investigated and appears to be very promising to follow the skin movement in the casting.展开更多
Sheet bulk metal forming processes have been widely developed to the facilitate manufacture of complicated 3D parts.However,there is still not enough know-how available.In this paper,as one of the typical sheet bulk m...Sheet bulk metal forming processes have been widely developed to the facilitate manufacture of complicated 3D parts.However,there is still not enough know-how available.In this paper,as one of the typical sheet bulk metal forming processes,the sheet metal extrusion process was studied.A reasonable finite element method(FEM)model of sheet metal extrusion process taking the influence of flow-stress curve with wide range of plastic strain and ductile damage into consideration was established and simulated by an arbitrary Lagrangian-Eulerian(ALE)FEM implemented in MSC.Marc.Validated by comparing the results with experiment,some phenomenological characteristics,such as metal flow behavior,shrinkage cavity,and the influence of different combinations of diameter of punch,diameter of extrusion outlet,and diameter of pre-punched hole were analyzed and concluded,which can be used as theoretical fundamental for the design of the sheet metal extrusion process.展开更多
The scope of the paper is the design of a fluid machinery with a multiphysics procedure, through CAD （computer-aided design）-CAE （computer-aided engineering）-CAx （computer-aided technologies） tools. The study of...The scope of the paper is the design of a fluid machinery with a multiphysics procedure, through CAD （computer-aided design）-CAE （computer-aided engineering）-CAx （computer-aided technologies） tools. The study of a wind turbine is a perfect example of a project that requires an interdisciplinary team design, in fact for such a project mechanical structure, and CFD （computational fluid dynamics） designers are necessary. In addition, in the last years, the multi domain design has been supported by the continuous development of software for computer-aided design and the unceasing increase of the connection between performances and computer costs： the final aim is to propose the instruments that assist the designer throughout all the steps of the project. The multi domain design, illustrated in this article, is based on how to design the wind turbine, and it is not about process management and manufacturability. In particular, in the article, the emphasis will be placed on the integration between CAD and mathematical software of general type and on the CAD-CAE integration.展开更多
Combining the strengths of Lagrangian and Eulerian descriptions,the coupled Lagrangian–Eulerian methods play an increasingly important role in various subjects.This work reviews their development and application in o...Combining the strengths of Lagrangian and Eulerian descriptions,the coupled Lagrangian–Eulerian methods play an increasingly important role in various subjects.This work reviews their development and application in ocean engineering.Initially,we briefly outline the advantages and disadvantages of the Lagrangian and Eulerian descriptions and the main characteristics of the coupled Lagrangian–Eulerian approach.Then,following the developmental trajectory of these methods,the fundamental formulations and the frameworks of various approaches,including the arbitrary Lagrangian–Eulerian finite element method,the particle-in-cell method,the material point method,and the recently developed Lagrangian–Eulerian stabilized collocation method,are detailedly reviewed.In addition,the article reviews the research progress of these methods with applications in ocean hydrodynamics,focusing on free surface flows,numerical wave generation,wave overturning and breaking,interactions between waves and coastal structures,fluid–rigid body interactions,fluid–elastic body interactions,multiphase flow problems and visualization of ocean flows,etc.Furthermore,the latest research advancements in the numerical stability,accuracy,efficiency,and consistency of the coupled Lagrangian–Eulerian particle methods are reviewed;these advancements enable efficient and highly accurate simulation of complicated multiphysics problems in ocean and coastal engineering.By building on these works,the current challenges and future directions of the hybrid Lagrangian–Eulerian particle methods are summarized.展开更多
基金the support from the National Natural Science Foundation of China(No.52472384)the Fundamental Research Funds for the Central Universities,China(No.G2024KY0615)+1 种基金sponsored by the Foundations of National Key Laboratory of Unmanned Aerial Vehicle Technology in NPU,(No.WR202411-2)the National Key Laboratory of Aircraft Configuration Design,China(No.JBGS-2024-01)。
文摘The hose-drogue system is a common method for soft aerial refueling,whereby the refueling tanker tows the drogue through the hose.In this paper,a mathematical-physical model of the hose-drogue system is developed and simulated using the Absolute Nodal Coordinate Formulation(ANCF)finite element method.A numerical solution program based on ANCF and ALE(Arbitrary Eulerian-Lagrange)-ANCF method was developed to simulate and analyze the horizontal and elongation release processes of the hose-drogue system at different towing points(underneath the wing and the belly of the aircraft).This program was developed by introducing an ALE description.The numerical solution program,developed based on the ANCF and ALE-ANCF methods,represents a significant advancement in computational efficiency for the rigid-flexible coupled multibody system of the air refueling hose-drogue system.This program can provide a valuable reference for the qualitative design of the hose-drogue multibody system in soft air refueling,while maintaining the necessary accuracy.
基金supported by the National Natural Science Foundation of China-Liaoning Joint Fund (U1508215)
文摘Solidifi cation shrinkage has been recognized as an important factor for macrosegregation formation. An arbitrary Lagrangian–Eulerian(ALE) model is constructed to predict the macrosegregation caused by thermal–solutal convection and solidi-fi cation shrinkage. A novel mesh update algorithm is developed to account for the domain change induced by solidifi cation shrinkage. The velocity–pressure coupling between the non-homogenous mass conservation equation and momentum equation is addressed by a modifi ed pressure correction method. The governing equations are solved by the streamline-upwind/Petrov–Galerkin-stabilized fi nite element algorithm. The application of the model to the Pb-19.2 wt%Sn alloy solidifi cation problem is considered. The inverse segregation is successfully predicted, and reasonable agreement with the literature results is obtained. Thus, the ALE model is established to be a highly effective tool for predicting the macrosegregation caused by solidifi cation shrinkage and thermal–solutal convection. Finally, the effect of solidifi cation shrinkage is analyzed. The results demonstrate that solidifi cation shrinkage delays the advance of the solidifi cation front and intensifi es the segregation.
基金This project is supported by National Natural Science Foundation of China(No.50505003).
文摘A two-dimensional finite element(FE)model for the high speed turning operations when orthogonally machining AISI H13 tool steel at 49HRC using poly crystalline cubic boron nitride(PCBN)is described.An arbitrary Lagrangian Eulerian(ALE)method has been adopted which does not need any chip separation criteria as opposed to the traditional Lagrangian approach.Through FE simulations temperature and stresses distributions are presented that could be helpful in predicting tool life and improving process parameters.The results show that high temperatures are generated along the tool rake face as compared to the shear zone temperatures due to high thermal conductivity of PCBN tools.
基金Project supported by the National Natural Science Foundation of China(Nos.11471048 and U1630249)the Foundation of Chinese Academy of Engineering Physics(No.2014A0202010)the Foundation of Laboratory of Computational Physics(No.9140C690202140C69293)
文摘The study of cylindrically symmetric compressible fluid is interesting from both theoretical and numerical points of view. In this paper, the typical spherical sym- metry properties of the numerical schemes are discussed, and an area weighted scheme is extended from a Lagrangian method to an arbitrary Lagrangian and Eulerian （ALE） method. Numerical results are presented to compare three discrete configurations, i.e., the control volume scheme, the area weighted scheme, and the plane scheme with the addition of a geometrical source. The fact that the singularity arises from the geometri- cal source term in the plane scheme is illustrated. A suggestion for choosing the discrete formulation is given when the strong shock wave problems are simulated.
文摘A computational procedure is developed to solve the problems of coupled motion of a structure and a viscous incompressible fluid. In order to incorporate the effect of the moving surface of the structure as well as the free surface motion, the arbitrary Lagrangian-Eulerian formulation is employed as the basis of the finite element spatial discretization. For numerical integration in time, the fraction,step method is used. This method is useful because one can use the same linear interpolation function for both velocity and pressure. The method is applied to the nonlinear interaction of a structure and a tuned liquid damper. All computations are performed with a personal computer.
文摘Sloshing has a widespread application in many industries including automotive, aerospace, ship building and motorcycle manufacturing. The goals of sloshing simulation is to first study the sloshing pattern and then improve the tank design to reduce noise levels, stresses on the structure and optimize the baffle arrangements. In this project simulation of the fluid in tank is studied and the design modification with baffle plate is considered to minimize the sloshing phenomena using Arbitrary Langrangian Eulerian （ALE） method. Also it is explained that there is need to analyze the sloshing phenomena in detail. Arbitrary Langrangian Eulerian finite element methods gain interest for the capability to control mesh geometry independently from material geometry, the ALE methods are used to create a new undistorted mesh for the fluid domain. In this paper we use the ALE technique to solve fuel slosh problem. Fuel slosh is an important design consideration not only for the fuel tank, but also for the structure supporting the fuel tank. Fuel slosh can be generated by many ways： abrupt changes in acceleration （braking）, as well as abrupt changes in direction （highway exit-ramp）. Repetitive motion can also be involved if a sloshing resonance is generated. These sloshing events can in turn affect the overall performance 0fthe parent structure. A finite element analysis method has been developed to analyze this complex event. A new ALE formulation for the fluid mesh can be used to keep the fluid mesh integrity during the motion of the tank. This paper explains the analysis capabilities on a technical level.
基金Project (2009A080205003) supported by the Major Science and Technology Project of Guangdong Province,ChinaProject (30815009) supported by the Foundation of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body,China
文摘The arbitrary Lagrangian-Eulerian（ALE） adaptive remeshing technology and the HyperXtrude software of transient finite element simulations were used on analogue simulation of aluminium extrusion processing.The field distributions of strain rate,stress,temperature and velocity of metal flow were obtained.The results are basically consistent with the experiment,which indicates that this method may successfully predict the defects in the actual extrusion process.
基金supported by the Prospective Joint Research Fund of the Jiangsu Provincial Department of Science and Technology Agency(No.BY2016073-11)
文摘The dynamic response performance of a large,cylindrical,fluid-filled steel container under high-speed impact is evaluated through fluid-structure interaction analysis using arbitrary Lagrange-Eulerian(ALE)method.The ALE method is adopted to accurately calculate the structural behavior induced by the internal liquid impact of the container.The stress and strain results obtained from the finite element analysis are in line with the experimental shell impact data.The influences of drop angle,drop height,and flow impact frequency are discussed.Calculation results indicate that the impact stress and damage of the container increase with drop height.However,the amplitude of the oscillation and the impact stress increase when the container and flow impact resonance occur at a certain drop height.The impact stress shows a nonlinear relationship with drop angle.
基金supported in part by the Aeronautical Science Foundation of China(No.20172952031)the Aeronautical Science Foundation of China (No.20142952026)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The fluid-structure interaction (FSI) between the canopy and flow field on the inflating and inflated conditions is investigated based on the arbitrary Lagrange-Euler (ALE) method,in both a single-and double-cruciform parachute systems.The projection area of canopy is calculated in the inflation process.The flow field characteristics and the interaction between canopies are analyzed.Results showed that,with free stream velocity of 50m/s,overinflation phenomenon would not occur during the inflation process of the double-cruciform-parachute system,because the collision and extrusion of the two canopies during inflation obstructed the oscillation of the inner gores.Concurrently,compared with the single-cruciform parachute,the vortex motion in the wake of double-cruciform-parachute is more intense.Thus the double-cruciform parachute system oscillated at a velocity of 50 m/s with an angle of less than 6.8°.By comparison,the oscillation angle of the single-cruciform parachute was within 3.5° at the velocity of 50m/s.The results are consistent with those of the wind tunnel test.
基金the support from the National Natural Science Foundation of China(No.51205007)the Specialized Research Fund for the Doctoral Program of Chinese Higher Education(No.20131102120019)
文摘A computational fluid dynamics （CFD） simulation method based on 3-D Navier Stokes equation and Arbitrary Lagrangian Eulerian （ALE） method is presented to analyze the grooved slip- per performance of piston pump. The moving domain of grooved slipper is transformed into a fixed reference domain by the ALE method, which makes it convenient to take the effects of rotate speed, body force, temperature, and oil viscosity into account. A geometric model to express the complex structure, which covers the orifice of piston and slipper, vented groove and the oil film, is constructed. Corresponding to different oil film thicknesses calculated in light of hydrostatic equilibrium theory and boundary conditions, a set of simulations is conducted in COMSOL to analyze the pump characteristics and effects of geometry （groove width and radius, orifice size） on these characteristics. Furthermore, the mechanics and hydraulics analyses are employed to validate the CFD model, and there is an excellent agreement between simulation and analytical results. The simulation results show that the sealing land radius, orifice size and groove width all dramatically affect the slipper behavior, and an optimum tradeoff among these factors is conducive to optimizing the pump design.
文摘Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.
基金This project is supported by National 863 Hi-Tech Project Foundation (No. 2002AA411030).
文摘An effective computational method is developed for dynamic analysis offluid-structure interaction problems involving large-amplitude sloshing of the fluid andlarge-displacement motion of the structure. The structure is modeled as a rigid container supportedby a system consisting of springs and dashpots. The motion of the fluid is decomposed into twoparts: the large-displacement motion with the container and the large-amplitude sloshing relative tothe container. The former is conveniently dealt with by defining a container-fixed noninertiallocal frame, while the latter is easily handled by adopting an ALE kinematical description. Thisleads to an easy and accurate treatment of both the fluid-structure interface and the fluid freesurface without producing excessive distortion of the computational mesh. The coupling between thefluid and the structure is accomplished through the coupling matrices that can be easilyestablished. Two numerical examples, including a TLD-structure system and a simplified liquid-loadedvehicle system, are presented to demonstrate the effectiveness and reliability of the proposedmethod. The present work can also be applied to simulate fluid-structure problems incorporatingmultibody systems and several fluid domains.
文摘Contaminated surfaces of the feedstock materials in aluminum alloy casting processes often produce various types of defects which can affect the tensile properties of the final products as well as their fatigue reliabilities.Semi-solid processing takes advantage of a much higher apparent viscosity of the die cast materials by limiting the risk of oxides formed at the free surfaces to become incorporated into the casting when the material is injected into the die.Most of existing semi-solid processes that use billets as feedstock material are however tied up with a different type of contaminated surface.During the injection phase,the external-skin on the periphery of the billet,which has been in contact with air and lubricant during the transfer in the shot sleeve,can be incorporated into the casting.When subjected to a heat treatment,the lubricant is decomposed and produces lens shape porosities.This might be a cause of reject for most structural parts.To avoid this kind of defects,the paths along which the billet skin evolves must be controlled during filling.In order to investigate the possibility of skin inclusion into cast parts during injection of the billet,a two-phase finite element mixture model is employed to model the metal flow.The formation of a skin on the periphery of the billet is modeled by setting an initial solid phase concentration profile in the radial direction.Microscopic observations of the real castings show that the approach is able to model the shear layers and to predict the paths along which the"lens porosity"defects could be formed.An Arbitrary Eulerian-Lagangian(ALE) method is also investigated and appears to be very promising to follow the skin movement in the casting.
基金supported by National Science&Technology Major Project of China(No.2009ZX04014-073)National Natural Science Foundation of China(No.50975175)
文摘Sheet bulk metal forming processes have been widely developed to the facilitate manufacture of complicated 3D parts.However,there is still not enough know-how available.In this paper,as one of the typical sheet bulk metal forming processes,the sheet metal extrusion process was studied.A reasonable finite element method(FEM)model of sheet metal extrusion process taking the influence of flow-stress curve with wide range of plastic strain and ductile damage into consideration was established and simulated by an arbitrary Lagrangian-Eulerian(ALE)FEM implemented in MSC.Marc.Validated by comparing the results with experiment,some phenomenological characteristics,such as metal flow behavior,shrinkage cavity,and the influence of different combinations of diameter of punch,diameter of extrusion outlet,and diameter of pre-punched hole were analyzed and concluded,which can be used as theoretical fundamental for the design of the sheet metal extrusion process.
文摘The scope of the paper is the design of a fluid machinery with a multiphysics procedure, through CAD （computer-aided design）-CAE （computer-aided engineering）-CAx （computer-aided technologies） tools. The study of a wind turbine is a perfect example of a project that requires an interdisciplinary team design, in fact for such a project mechanical structure, and CFD （computational fluid dynamics） designers are necessary. In addition, in the last years, the multi domain design has been supported by the continuous development of software for computer-aided design and the unceasing increase of the connection between performances and computer costs： the final aim is to propose the instruments that assist the designer throughout all the steps of the project. The multi domain design, illustrated in this article, is based on how to design the wind turbine, and it is not about process management and manufacturability. In particular, in the article, the emphasis will be placed on the integration between CAD and mathematical software of general type and on the CAD-CAE integration.
基金the support received from the Laoshan Laboratory(No.LSKJ202202000)the National Natural Science Foundation of China(Grant Nos.12032002,U22A20256,and 12302253)the Natural Science Foundation of Beijing(No.L212023)for partially funding this work.
文摘Combining the strengths of Lagrangian and Eulerian descriptions,the coupled Lagrangian–Eulerian methods play an increasingly important role in various subjects.This work reviews their development and application in ocean engineering.Initially,we briefly outline the advantages and disadvantages of the Lagrangian and Eulerian descriptions and the main characteristics of the coupled Lagrangian–Eulerian approach.Then,following the developmental trajectory of these methods,the fundamental formulations and the frameworks of various approaches,including the arbitrary Lagrangian–Eulerian finite element method,the particle-in-cell method,the material point method,and the recently developed Lagrangian–Eulerian stabilized collocation method,are detailedly reviewed.In addition,the article reviews the research progress of these methods with applications in ocean hydrodynamics,focusing on free surface flows,numerical wave generation,wave overturning and breaking,interactions between waves and coastal structures,fluid–rigid body interactions,fluid–elastic body interactions,multiphase flow problems and visualization of ocean flows,etc.Furthermore,the latest research advancements in the numerical stability,accuracy,efficiency,and consistency of the coupled Lagrangian–Eulerian particle methods are reviewed;these advancements enable efficient and highly accurate simulation of complicated multiphysics problems in ocean and coastal engineering.By building on these works,the current challenges and future directions of the hybrid Lagrangian–Eulerian particle methods are summarized.
