This numerical simulation investigates the two⁃phase flow under the condition of supercooled large droplets impinging on the aircraft surface.Based on Eulerian framework,a method for calculating supercooled water drop...This numerical simulation investigates the two⁃phase flow under the condition of supercooled large droplets impinging on the aircraft surface.Based on Eulerian framework,a method for calculating supercooled water droplet impingement characteristics is established.Then,considering the deformation and breaking effects during the movement,this method is extended to calculate the impingement characteristics of supercooled large droplets,as well as the bouncing and splashing effects during impingement.The impingement characteristics of supercooled large droplets is then investigated by this method.The results demonstrate that the deformation and breaking effects of supercooled large droplets have negligible influence on the impingement characteristics under the experimental conditions of this paper.In addition,the results of the impingement range and collection efficiency decrease when considering the bouncing and splashing effects.The bouncing effect mainly affects the mass loss near the impingement limits,while the splashing effect influences the result around the stagnation point.This investigation is beneficial for the analysis of aircraft icing and the design of anti⁃icing system with supercooled large droplet conditions.展开更多
Eulerian method is a main numerical simulation method in elastoplastic hydrodynamics, which is suitable for the problems with multi-component and large deformation. As the feature of the problems to be simulated, such...Eulerian method is a main numerical simulation method in elastoplastic hydrodynamics, which is suitable for the problems with multi-component and large deformation. As the feature of the problems to be simulated, such as detonation and penetration, the dynamic parallel method （DPM） is designed to adjust the computational domain dynamically to get better load balance. Dynamic parallel method can be separated into two parts： one is division of initial computational domain and location of the data, the other is expansion of the computational domain and adjustment of the data location. DPM program can greatly shorten computational time and be preferable in simulating actual problems. The speedup of the DPM program is linear in parallel test. DPM can be popularized to parallel program of other multi-component high dimension Eulerian methods naturally.展开更多
An Arbitrary Lagrangian-Eulerian(ALE) method was employed to simulate the sheet metal extrusion process,aiming at avoiding mesh distortion and improving the computational accuracy.The method was implemented based on M...An Arbitrary Lagrangian-Eulerian(ALE) method was employed to simulate the sheet metal extrusion process,aiming at avoiding mesh distortion and improving the computational accuracy.The method was implemented based on MSC/MARC by using a fractional step method,i.e.a Lagrangian step followed by an Euler step.The Lagrangian step was a pure updated Lagrangian calculation and the Euler step was performed using mesh smoothing and remapping scheme.Due to the extreme distortion of deformation domain,it was almost impossible to complete the whole simulation with only one mesh topology.Therefore,global remeshing combined with the ALE method was used in the simulation work.Based on the numerical model of the process,some deformation features of the sheet metal extrusion process,such as distribution of localized equivalent plastic strain,and shrinkage cavity,were revealed.Furthermore,the differences between conventional extrusion and sheet metal extrusion process were also analyzed.展开更多
A new flux-based hybrid subcell-remapping algorithm for staggered multimaterial arbitrary Lagrangian-Eulerian (MMALE) methods is presented. This new method is an effective generalization of the original subcell-remapp...A new flux-based hybrid subcell-remapping algorithm for staggered multimaterial arbitrary Lagrangian-Eulerian (MMALE) methods is presented. This new method is an effective generalization of the original subcell-remapping method to the multi-material regime (LOUBERE, R. and SHASHKOV,M. A subcell remapping method on staggered polygonal grids for arbitrary-Lagrangian-Eulerian methods. Journal of Computational Physics, 209, 105–138 (2005)). A complete remapping procedure of all fluid quantities is described detailedly in this paper. In the pure material regions, remapping of mass and internal energy is performed by using the original subcell-remapping method. In the regions near the material interfaces, remapping of mass and internal energy is performed with the intersection-based fluxes where intersections are performed between the swept regions and pure material polygons in the Lagrangian mesh, and an approximate approach is then introduced for constructing the subcell mass fluxes. In remapping of the subcell momentum, the mass fluxes are used to construct the momentum fluxes by multiplying a reconstructed velocity in the swept region. The nodal velocity is then conservatively recovered. Some numerical examples simulated in the full MMALE regime and several purely cyclic remapping examples are presented to prove the properties of the remapping method.展开更多
We present a simple and efficient strategy for the acceleration of explicit Eulerian methods for multidimensional hyperbolic systems of conservation laws.The strategy is based on the Galilean invariance of dynamic equ...We present a simple and efficient strategy for the acceleration of explicit Eulerian methods for multidimensional hyperbolic systems of conservation laws.The strategy is based on the Galilean invariance of dynamic equations and optimization of the reference frame,in which the equations are numerically solved.The optimal reference frame moves(locally in time)with the average characteristic speed of the system,and,in this sense,the resulting method is quasi-Lagrangian.This leads to the acceleration of the numerical computations thanks to the optimal CFL condition and automatic adjustment of the computational domain to the evolving part of the solution.We show that our quasi-Lagrangian acceleration procedure may also reduce the numerical dissipation of the underlying Eulerian method.This leads to a significantly enhanced resolution,especially in the supersonic case.We demonstrate a great potential of the proposed method on a number of numerical examples.展开更多
In this paper, we incorporate fuzzy mathematics approach into the Eulerian method to simulate three dimensional multi-material interfaces. In particular, we propose a fuzzy interface treatment for describing interface...In this paper, we incorporate fuzzy mathematics approach into the Eulerian method to simulate three dimensional multi-material interfaces. In particular, we propose a fuzzy interface treatment for describing interfaces, designing transport plans, and computing transport quantities. Using a set of three-dimensional inviscid isothermal elastic-plastic hydrodynamic equations, we simulate shaped charge jet in different filled dynamite structures. Strain and stress have been under consideration in simulations. Numerical results demonstrate that the fuzzy interface treatment is correct and efficient for three-dimensional multi-material problems.展开更多
n the area of naval architecture and ocean engineering,the research about the underwater xplosion problem is of great significance.To achieve prolonged simulation of near-free surface underwater explosion,the underwat...n the area of naval architecture and ocean engineering,the research about the underwater xplosion problem is of great significance.To achieve prolonged simulation of near-free surface underwater explosion,the underwater explosion transient numerical model is established in this paper based on compressible Eulerian finite element method(EFEM).Compared with Geers Hunter formula,EFEM is availably validated by simulating the free-field underwater xplosion case.Then,the bubble pulsation and flow field dynamic characteristics of the cases with different underwater explosive depth are compared in this work.Lastly,the height of the water hump and the pressure of flow flied are analyzed quantitatively through the simulation results.展开更多
A difference scheme in curvilinear coordinates is put forward for calculation of salinity in estuaries and coastal waters, which is based on Eulerian-Lagrangian method. It combines first-order and second-order Lagrang...A difference scheme in curvilinear coordinates is put forward for calculation of salinity in estuaries and coastal waters, which is based on Eulerian-Lagrangian method. It combines first-order and second-order Lagrangian interpolation to reduce numerical dispersion and oscillation. And the length of the curvilinear grid is also considered in the interpolation. Then the scheme is used in estuary, coast and ocean model, and several numerical experiments for the Yangtze Estuary and the Hangzhou Bay are conducted to test it. These experiments show that it is suitable for simulations of salinity in estuaries and coastal waters with the models using curvilinear coordinates.展开更多
The Eulerian？Lagrangian method（ELM） has been used by many ocean models as the solution of the advection equation,but the numerical error caused by interpolation imposes restriction on its accuracy.In the present st...The Eulerian？Lagrangian method（ELM） has been used by many ocean models as the solution of the advection equation,but the numerical error caused by interpolation imposes restriction on its accuracy.In the present study,hybrid N-order Lagrangian interpolation ELM（Li ELM） is put forward in which the N-order Lagrangian interpolation is used at first,then the lower order Lagrangian interpolation is applied in the points where the interpolation results are abnormally higher or lower.The calculation results of a step-shaped salinity advection model are analyzed,which show that higher order（N=3？8） Li ELM can reduce the mean numerical error of salinity calculation,but the numerical oscillation error is still significant.Even number order Li ELM makes larger numerical oscillation error than its adjacent odd number order Li ELM.Hybrid N-order Li ELM can remove numerical oscillation,and it significantly reduces the mean numerical error when N is even and the current is in fixed direction,while it makes less effect on mean numerical error when N is odd or the current direction changes periodically.Hybrid odd number order Li ELM makes less mean numerical error than its adjacent even number order Li ELM when the current is in the fixed direction,while the mean numerical error decreases as N increases when the current direction changes periodically,so odd number of N may be better for application.Among various types of Hybrid N-order Li ELM,the scheme reducing N-order directly to 1st-order may be the optimal for synthetic selection of accuracy and computational efficiency.展开更多
冰晶结冰是威胁航空飞行安全的重要因素之一,研究冰风洞的结冰机理是研究高空冰晶结冰的重要基础。采用基于欧拉方法的数值模拟,实现冰风洞流场与粒子参数的双向耦合,以NRC大尺寸冰风洞为模型,计算分析了风洞进口不同平均体积直径(Media...冰晶结冰是威胁航空飞行安全的重要因素之一,研究冰风洞的结冰机理是研究高空冰晶结冰的重要基础。采用基于欧拉方法的数值模拟,实现冰风洞流场与粒子参数的双向耦合,以NRC大尺寸冰风洞为模型,计算分析了风洞进口不同平均体积直径(Median Volume Diameter,MVD)、总含水量(Total Water Content,TWC)以及相对湿度的情况下,粒子温度、液态水占总含水量的比例(Liquid Water Content/Total Water Content,LWC/TWC)、MVD以及流场温度等粒子和流场参数的沿程变化规律。结果表明:粒子运动速度受MVD、TWC和相对湿度的影响均不大;粒子温度变化受相对湿度影响较大,TWC的增加增大了粒子与流场整体的热交换;风洞出口MVD的大小受初始MVD大小、TWC以及相对湿度的影响均较大;受风洞收缩型构型以及粒子在风洞中的换热影响,空气温度沿流程是降低的,相对湿度沿程是增加的。初始TWC、MVD和相对湿度的变化均对风洞沿程的流场温度和相对湿度造成影响;增大TWC、增加MVD以及增大相对湿度,均有利于在风洞出口形成冰晶。展开更多
基金supported in part by the National Natural Science Foundation of China(No.51806008)the Open Fund of Key Laboratory of Rotor Aerodynamics Key Laboratory(No.RAL202104-2)。
文摘This numerical simulation investigates the two⁃phase flow under the condition of supercooled large droplets impinging on the aircraft surface.Based on Eulerian framework,a method for calculating supercooled water droplet impingement characteristics is established.Then,considering the deformation and breaking effects during the movement,this method is extended to calculate the impingement characteristics of supercooled large droplets,as well as the bouncing and splashing effects during impingement.The impingement characteristics of supercooled large droplets is then investigated by this method.The results demonstrate that the deformation and breaking effects of supercooled large droplets have negligible influence on the impingement characteristics under the experimental conditions of this paper.In addition,the results of the impingement range and collection efficiency decrease when considering the bouncing and splashing effects.The bouncing effect mainly affects the mass loss near the impingement limits,while the splashing effect influences the result around the stagnation point.This investigation is beneficial for the analysis of aircraft icing and the design of anti⁃icing system with supercooled large droplet conditions.
基金Sponsored by State Key Laboratory of Computational Physics Fundation(9140C690101070C69)
文摘Eulerian method is a main numerical simulation method in elastoplastic hydrodynamics, which is suitable for the problems with multi-component and large deformation. As the feature of the problems to be simulated, such as detonation and penetration, the dynamic parallel method （DPM） is designed to adjust the computational domain dynamically to get better load balance. Dynamic parallel method can be separated into two parts： one is division of initial computational domain and location of the data, the other is expansion of the computational domain and adjustment of the data location. DPM program can greatly shorten computational time and be preferable in simulating actual problems. The speedup of the DPM program is linear in parallel test. DPM can be popularized to parallel program of other multi-component high dimension Eulerian methods naturally.
基金Project(50505027) supported by the National Natural Science Foundation of ChinaProject(20070248056) supported by the Research Fund for the Doctoral Program of Higher Education of China
文摘An Arbitrary Lagrangian-Eulerian(ALE) method was employed to simulate the sheet metal extrusion process,aiming at avoiding mesh distortion and improving the computational accuracy.The method was implemented based on MSC/MARC by using a fractional step method,i.e.a Lagrangian step followed by an Euler step.The Lagrangian step was a pure updated Lagrangian calculation and the Euler step was performed using mesh smoothing and remapping scheme.Due to the extreme distortion of deformation domain,it was almost impossible to complete the whole simulation with only one mesh topology.Therefore,global remeshing combined with the ALE method was used in the simulation work.Based on the numerical model of the process,some deformation features of the sheet metal extrusion process,such as distribution of localized equivalent plastic strain,and shrinkage cavity,were revealed.Furthermore,the differences between conventional extrusion and sheet metal extrusion process were also analyzed.
基金Project supported by the China Postdoctoral Science Foundation(No.2017M610823)
文摘A new flux-based hybrid subcell-remapping algorithm for staggered multimaterial arbitrary Lagrangian-Eulerian (MMALE) methods is presented. This new method is an effective generalization of the original subcell-remapping method to the multi-material regime (LOUBERE, R. and SHASHKOV,M. A subcell remapping method on staggered polygonal grids for arbitrary-Lagrangian-Eulerian methods. Journal of Computational Physics, 209, 105–138 (2005)). A complete remapping procedure of all fluid quantities is described detailedly in this paper. In the pure material regions, remapping of mass and internal energy is performed by using the original subcell-remapping method. In the regions near the material interfaces, remapping of mass and internal energy is performed with the intersection-based fluxes where intersections are performed between the swept regions and pure material polygons in the Lagrangian mesh, and an approximate approach is then introduced for constructing the subcell mass fluxes. In remapping of the subcell momentum, the mass fluxes are used to construct the momentum fluxes by multiplying a reconstructed velocity in the swept region. The nodal velocity is then conservatively recovered. Some numerical examples simulated in the full MMALE regime and several purely cyclic remapping examples are presented to prove the properties of the remapping method.
基金The work of A.Kurganov was supported in part by NSF grants DMS-0310585 and DMS-0610430.
文摘We present a simple and efficient strategy for the acceleration of explicit Eulerian methods for multidimensional hyperbolic systems of conservation laws.The strategy is based on the Galilean invariance of dynamic equations and optimization of the reference frame,in which the equations are numerically solved.The optimal reference frame moves(locally in time)with the average characteristic speed of the system,and,in this sense,the resulting method is quasi-Lagrangian.This leads to the acceleration of the numerical computations thanks to the optimal CFL condition and automatic adjustment of the computational domain to the evolving part of the solution.We show that our quasi-Lagrangian acceleration procedure may also reduce the numerical dissipation of the underlying Eulerian method.This leads to a significantly enhanced resolution,especially in the supersonic case.We demonstrate a great potential of the proposed method on a number of numerical examples.
基金the National Natural Science Foundation of China (Grant No.10272023).
文摘In this paper, we incorporate fuzzy mathematics approach into the Eulerian method to simulate three dimensional multi-material interfaces. In particular, we propose a fuzzy interface treatment for describing interfaces, designing transport plans, and computing transport quantities. Using a set of three-dimensional inviscid isothermal elastic-plastic hydrodynamic equations, we simulate shaped charge jet in different filled dynamite structures. Strain and stress have been under consideration in simulations. Numerical results demonstrate that the fuzzy interface treatment is correct and efficient for three-dimensional multi-material problems.
基金The authors would like to acknowledge the support of the National Natural Science Foundation of China(Grant 11672081)the Industrial Technology Development Program(Grants JCKY2018604C010 and JCKY2017604C002).Finally,Thanks for the help of Zu-Hui Li during writing the paper.
文摘n the area of naval architecture and ocean engineering,the research about the underwater xplosion problem is of great significance.To achieve prolonged simulation of near-free surface underwater explosion,the underwater explosion transient numerical model is established in this paper based on compressible Eulerian finite element method(EFEM).Compared with Geers Hunter formula,EFEM is availably validated by simulating the free-field underwater xplosion case.Then,the bubble pulsation and flow field dynamic characteristics of the cases with different underwater explosive depth are compared in this work.Lastly,the height of the water hump and the pressure of flow flied are analyzed quantitatively through the simulation results.
基金This project was supported by the Major State Basic Research Program under Contract Grant No. G1999043803the University Fund for Mainstay Teachers of State Ministry of Education and the Opening Fund of Open Laboratory of Marine Dynamic Process and Sa
文摘A difference scheme in curvilinear coordinates is put forward for calculation of salinity in estuaries and coastal waters, which is based on Eulerian-Lagrangian method. It combines first-order and second-order Lagrangian interpolation to reduce numerical dispersion and oscillation. And the length of the curvilinear grid is also considered in the interpolation. Then the scheme is used in estuary, coast and ocean model, and several numerical experiments for the Yangtze Estuary and the Hangzhou Bay are conducted to test it. These experiments show that it is suitable for simulations of salinity in estuaries and coastal waters with the models using curvilinear coordinates.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.40906044 and 41076048)the Fundamental Research Funds for the Central Universities Project(Grant No.2011B05714)
文摘The Eulerian？Lagrangian method（ELM） has been used by many ocean models as the solution of the advection equation,but the numerical error caused by interpolation imposes restriction on its accuracy.In the present study,hybrid N-order Lagrangian interpolation ELM（Li ELM） is put forward in which the N-order Lagrangian interpolation is used at first,then the lower order Lagrangian interpolation is applied in the points where the interpolation results are abnormally higher or lower.The calculation results of a step-shaped salinity advection model are analyzed,which show that higher order（N=3？8） Li ELM can reduce the mean numerical error of salinity calculation,but the numerical oscillation error is still significant.Even number order Li ELM makes larger numerical oscillation error than its adjacent odd number order Li ELM.Hybrid N-order Li ELM can remove numerical oscillation,and it significantly reduces the mean numerical error when N is even and the current is in fixed direction,while it makes less effect on mean numerical error when N is odd or the current direction changes periodically.Hybrid odd number order Li ELM makes less mean numerical error than its adjacent even number order Li ELM when the current is in the fixed direction,while the mean numerical error decreases as N increases when the current direction changes periodically,so odd number of N may be better for application.Among various types of Hybrid N-order Li ELM,the scheme reducing N-order directly to 1st-order may be the optimal for synthetic selection of accuracy and computational efficiency.
文摘冰晶结冰是威胁航空飞行安全的重要因素之一,研究冰风洞的结冰机理是研究高空冰晶结冰的重要基础。采用基于欧拉方法的数值模拟,实现冰风洞流场与粒子参数的双向耦合,以NRC大尺寸冰风洞为模型,计算分析了风洞进口不同平均体积直径(Median Volume Diameter,MVD)、总含水量(Total Water Content,TWC)以及相对湿度的情况下,粒子温度、液态水占总含水量的比例(Liquid Water Content/Total Water Content,LWC/TWC)、MVD以及流场温度等粒子和流场参数的沿程变化规律。结果表明:粒子运动速度受MVD、TWC和相对湿度的影响均不大;粒子温度变化受相对湿度影响较大,TWC的增加增大了粒子与流场整体的热交换;风洞出口MVD的大小受初始MVD大小、TWC以及相对湿度的影响均较大;受风洞收缩型构型以及粒子在风洞中的换热影响,空气温度沿流程是降低的,相对湿度沿程是增加的。初始TWC、MVD和相对湿度的变化均对风洞沿程的流场温度和相对湿度造成影响;增大TWC、增加MVD以及增大相对湿度,均有利于在风洞出口形成冰晶。
