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Key Technologies of Coupling for Multiphysics in Numerical Reactor DENG Li, SHI Dunfu, LI Gang CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2016, 33 (6): 631-638.   Abstract （1066）   HTML （116）    PDF （1623KB）（3453）       Knowledge map    With rapid development of computer and super computation, coupling for multi-physics,multi-scale and multi-process has become possible. Some lone process are integrated together. Some approximates from experience will be removed after all of the processes to be considered. This work is based on a virtual reactor. The goal is to improve precision by improvement of modeling and high fidelity computation. At present, study measures are changed from experiment and engineer dependent to theory analysis and numerical simulation. Numerical simulation will become more and more important. In this paper, CASL and NURESAFE are introduced. Then, several challenges, which include key technologies of software, are put forward in development of nuclear energy. Finally, suggestions are given for numerical reactor. It is only for reference and discussion. Reference | Related Articles | Metrics

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Study on Extreme Plasma Dynamics by Quantum Electrodynamic Particle-in-Cell Simulations CHANG Hengxin, XU Zheng, YAO Weipeng, XIE Yu, QIAO Bin CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2017, 34 (5): 526-542.   Abstract （1036）   HTML （25）    PDF （4769KB）（3481）       Knowledge map    Next generation petawatt laser facility is expected to reach intensity up to the order of 1023-1024 W·cm-2,which may generate electromagnetic fields so strong that nonlinear quantum electrodynamics (QED) processes play a crucial role in plasma dynamics.A large number of γ photons can be emitted through synchrotron radiation from ultrarelativistic electrons,and pair creation process can also be triggered when γ photons traverse electromagnetic fields.In turn,these QED physics can affect plasma dynamics itself significantly,in particular for electron motion under radiation reaction.In order to study such extreme plasma dynamics,we introduce a QED model developed in recent years,which can be coupled with traditional particle-in-cell (PIC) code,i.e.,so-called a QED-PIC code.Due to booming particle number caused by the newly emitted photons and created pairs,we also develop a particle merge algorithm to reduce the computational scale.Several applications of this contemporary QED-PIC code in modeling of ultraintense laser-plasma interaction and extreme astrophysical phenomena are presented. Reference | Related Articles | Metrics

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Thyristor Latching Current and Maintain Current TAN Wei, LI Jianqing CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2015, 32 (6): 729-734.   Abstract （1025）      PDF （1318KB）（1659）       Knowledge map    Thyristor latching current and maintaining current have important effects on its working state. With thyristor conduction characteristics latching current is derived from carrier density; Based on current gain of NPN transistor, maintaining current is obtained. Compared with simulation results of Sentaurus TCAD software, calculated results have good agreement. It shows correctness of the formula. Related Articles | Metrics

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Numerical Simulation on Nonlinear Evolution of Magneto-Rayleigh-Taylor Instability CAO Qiwei, XIAO Delong, YANG Xianjun, WANG Jianguo Chinese Journal of Computational Physics    2021, 38 (1): 5-15.   DOI: 10. 19596/ j. cnki. 1001-246x. 8237 Abstract （953）   HTML （115）    PDF （10495KB）（1095）       Knowledge map    A 2D numerical simulation program is developed for nonlinear evolution of magneto-Rayleigh-Taylor instability(MRTI). Based on an ideal magnetohydrodynamic model, a 5th WENO scheme is employed to calculate MHD equations and a projection scheme is used to clean spurious magnetic field divergence. The method is validated with MRTI compared with theory of linear stability. It is shown that the vertical magnetic field suppresses evidently MRTI in both linear and nonlinear stages. The parallel magnetic field has weak effect on MRTI in linear stage. However, it reduces remarkably Kelvin-Helmholtz instability and overall instability in nonlinear regime. High order harmonic occurs in the nonlinear evolution of single mode, and many modes except fundamental modes and harmonic occur in the evolution of double modes. In MRT evolution of multi-mode seeds inverse cascade occur, which means that perturbations evolve from short wavelength to long wavelength in the nonlinear stage. Reference | Related Articles | Metrics

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Lattice Boltzmann Simulation of Mixed Convection in an Enclosure Filled with Porous Medium WANG Tingting, GAO Qiang, CHEN Jian, XU Hongtao, YANG Mo CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2017, 34 (1): 39-46.   Abstract （952）   HTML （0）    PDF （3388KB）（2282）       Knowledge map    Lattice Boltzmann method is adopted to investigate mixed convection in an enclosure filled with porous medium.A heated cylinder (D/L=0.4) is located at center of the enclosure with high temperature.Inlet flow with low temperature is located at lower-left wall of the enclosure and exit is at upper-left wall.Other walls are assumed adiabatic.Influences of Richardson number Ri and Darcy number Da on average Nusselt number Nu around heated cylinder are investigated while Prandtl and Grashof numbers are kept at 0.71 and 1.4×104, respectively.It indicates that Nu decreases with increasing Ri.Influence of Richardson number on Nu is significant as Darcy number is great.At 10-5≤Da≤10-2, Nu increases with increasing Darcy number as forced convection dominates flow (Ri≤0.1).As natural convection dominates flow (Ri=10), Nu is not sensitive to Darcy number. Reference | Related Articles | Metrics

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An Integrated High-throughput Computational Material Platform YANG Xiaoyu, WANG Juan, REN Jie, SONG Jianlong, WANG Zongguo, ZENG Zhi, ZHANG Xiaoli, HUANG Sunchao, ZHANG Ping, LIN Haiqing CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2017, 34 (6): 697-704.   Abstract （910）   HTML （16）    PDF （2633KB）（2829）       Knowledge map    The core philosophy of Material Genome Initiative is transition of way of new material design from traditional "try-and-error" approach to in-silico material design approach where intensive computing and material informatics are employed. It aims to effectively speed up discovery, development, production and deployment of new material two times faster as it is now. It means a culture shift of new material discovery:simulation and prediction first, followed by experiment. An integrated computational material platform that can facilitate high-throughput quantum mechanical simulations and manage simulation lifecycle data is therefore vital. This paper depicts a high throughput computational material platform and software framework, namely, MatCloud, which effectively integrates individual quantum mechanical simulation tasks, data extraction and data storage into an automatic flow in an end-to-end manner without direct human control. Especially, core data curation activities are also integrated into this flow rather than happening at post-simulation stage separately. MatCloud is demonstrated in an example of disorder binary alloy design to be valid and effective. Reference | Related Articles | Metrics

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THE CALCULATION AND THE MAIN FEATURES OF η<0 COULOMB WAVE FUNCTION Fang Dufei, Wang Yansen, Huang Fayang, Shi Wei CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    1991, 8 (1): 88-94.   Abstract （881）      PDF （392KB）（1246）       Knowledge map    A approach of the calculation for the regular Coulomb wave function Ft (η,ρ) (η<0)and its main features depended on η,l and ρ are described. A example about their applications to integral calculations in electron-ion collision is given. Related Articles | Metrics

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Interview archives: The world as I see it Jie LIU, Shuo HUANG, Wenjuan LYU, Ying YUE Chinese Journal of Computational Physics    2021, 38 (3): 253-256.   Abstract （866）   HTML （252）    PDF （2903KB）（2024）       Knowledge map    Reference | Related Articles | Metrics

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Theoretical Study on Electronic Structure and Optical Properties of GaN:TM(TM=V, Cr, Mn, Fe, Co, Ni) DONG Yanfeng, LI Ying CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2016, 33 (4): 490-498.   Abstract （832）   HTML （0）    PDF （6320KB）（2081）       Knowledge map    Electronic structure and optical properties of GaN systems doped with transition metals (GaN:TM, TM=V, Cr, Mn, Fe, Co, Ni) are studied with first-principles calculations. Influences of transition metals on electronic structure and optical properties are discussed. It shows that doped materials are direct semiconductors with half-metal property except Fe-doped material. Transition metal impurity introduces defect levels in energy gap of GaN, which is contributed by 3d electron states of transition metals. For GaN:V, Cr, Mn, Co, absorption peaks appear near defect level in low energy region. These peaks can be attributed to transiton between 3d electrons and N-2p electrons. Reference | Related Articles | Metrics

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Boundary Conditions in Lattice Boltzmann Method NIE De-ming, LIN Jian-zhong CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2004, 21 (1): 21-26.   Abstract （819）      PDF （250KB）（3774）       Knowledge map    Comparison and discussion of several boundary conditions in lattice Boltzmann method are presented. To achieve improved accuracy, a new method based on the idea of standard bounce-back scheme is proposed. Numerical simulations for two-dimensional Poiseuille flow and unsteady Couette flow are carried out using d2q9 model, and the results are identical to the analytical solutions. The convergence for different boundary treatments is discussed by changing single relaxation time τ and Re number. The results show that LBM can recover Navier-Stokes equation at low Mach number. It is also indicated that the errors for large τ are much bigger than those for τ close to 1. Related Articles | Metrics

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Efficient Algorithm for Stiff Source Terms in Strongly Coupling Radiative Transfer and Electron Energy Equations LI Ruo, LI Weiming, SONG Peng CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2017, 34 (3): 253-260.   Abstract （783）   HTML （1）    PDF （1111KB）（1797）       Knowledge map    We study numerical methods for coupled radiative transfer and electron energy equations. In highly opaque materials, strong coupling between them results in stiff source terms, making design of efficient and stable algorithms a challenging task. In this paper, we develop an efficient algorithm for multi-group radiative transfer equations coupled with electron energy equations. It is an integration method based on an ansatz of electron temperature. It poses no constraint on time step, and gives physically relevent solutions under reasonable assumptions. Numerical results show that the method is highly efficient and accurate. Reference | Related Articles | Metrics

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First-Principles Simulation on Structure-Property of Ti-Al Intermetallic Compounds TAN Junhua, ZHU Kaijin, PENG Junhui CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2017, 34 (3): 365-373.   Abstract （780）   HTML （4）    PDF （2403KB）（2010）       Knowledge map    Crystal structure, mechanical and electronic properties of Ti-Al intermetallic compounds were studied using first-principles implemented in CASTEP. At 0 K, 0 GPa, thermodynamically stable structures are TiAl3, TiAl2, TiAl, Ti3Al. Unit cells of TiAl3, TiAl2, TiAl are evolutions of face-centered cubic Al. Structure of Ti3Al is similar to Ti, which is hexagonal close packing structure. Mechanical properties were calculated. It was found that with increasing of Ti molar fraction, their bulk modulus are approximate equivalent. But shear modulus and Vickers hardness decrease, and so did Pugh ratios. It shows that toughness became better. At last, density of state and Mulliken population analysis were simulated. Bonding nature of Ti-Al is a combination of metallic, covalent and weak ionic. Reference | Related Articles | Metrics

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High Order Schemes for CFD: A Review CHENG Juan, SHU Chi-Wang CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2009, 26 (5): 633-655.   Abstract （769）      PDF （1273KB）（1924）       Knowledge map    Over the past two decades there have been many research activities in the design and application of high order accurate numerical methods in computational fluid dynamics (CFD). High order methods are especially desirable for simulating flows with complicated solution structures. We give a review on the development and application of several classes of high order schemes in CFD, mainly concentrating on the simulation of compressible flows. An important feature of the compressible flow is the existence of shocks, interfaces and other discontinuities and often also complicated structure in the smooth part of the solution. This gives a unique challenge to the design of high order schemes to be non-oscillatory and yet still maintaining their high order accuracy. We concentrate our discussion on the essentially non-oscillatory (ENO), weighted ENO (WENO) finite difference,finite volume schemes and discontinuous Galerkin (DG) finite element methods. We attempt to describe their main properties and their relative strength and weakness. We also briefly review their developments and applications, concentrating mainly on the results over the past five years. Related Articles | Metrics

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Discontinuous Finite Element Methods for Solving Hydrodynamic Equations YU Xi-jun, ZHOU Tie CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2005, 22 (2): 108-116.   Abstract （768）      PDF （509KB）（3232）       Knowledge map    The discontinuous finite element method with first, second and third order accuracy on triangular meshes on two-dimensional domain is applied to simulate hydrodynamic equations. The calculation results are compared with those from difference methods. It is reckoned that the discontinuous finite element method has advantages in solving hydrodynamic problems with complicated boundary conditions or a domain with a complicated boundary. Related Articles | Metrics

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Progress in Research on Stochastic Neutron Dynamics and Its Numerical Simulation YANG Junyun, YING Yangjun, XIAO Gang CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2017, 34 (2): 127-141.   Abstract （763）   HTML （119）    PDF （2459KB）（3318）       Knowledge map    Stochastic neutron dynamics is important task in nuclear power plant design and nuclear reactor safety. In this paper, basic concepts and research methods for stochastic neutron kinetics are introduced and historical development and research status in the field are sketched out. Multiplicities of fission neutrons and photons are main sources of zero power reactor noise. Based on description equation of neutron fluctuation and its solution, stochastic theory of zero power and power reactor noise is evolved. Stochastic neutron dynamics are applied in important areas such as reactivity microscopic measurement, power reactor noise measurement and analysis, nuclear criticality excursion analysis, nuclear material detection and identification and so on. In the past half century, however, it lacks available method and tool to implement quantitative analysis of problems such as probability distribution of burst waiting time of neutron initiation in pulse reactor. In recent years, important progress is made in generalized semi-Markov process simulation method, which is applied to stochastic neutron kinetic process simulation. It reveals inherent law of neutron initiation experiments conducted in pulse reactor. At last, research topics to be solved in stochastic neutron dynamics are discussed. Reference | Related Articles | Metrics

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A Fast Node Placement Method with Bubble Simulation QI Nan, NIE Yufeng, ZHANG Weiwei CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2012, 29 (3): 333-339.   Abstract （746）      PDF （1273KB）（1230）       Knowledge map    Node placement method with bubble simulation can generate high-qualify node sets in complex domains.However,its efficiency needs to be increased.Several modifications were done to reduce the cost of simulation.Firstly,let viscosity coefficient c gradually increases instead of being taken as a constant.It speeds up convergency.Moreover,at the end of each round simulation,in which bubbles additions or deletions are operated,c is assigned to a small value in order to ensure quality of bubble distribution.Secondly,as solving ordinary differential equations that control movement of bubbles,a low order numerical algorithm is chosen.Finally,sort process of overlapping rate of bubbles is removed.It is replaced by setting only threshold for bubbles additions and deletions.Numerial examples show that computing cost decreases by approximately 40% and average quality of Delaunay triangulation corresponding to node set is over 0.9.It shows that the algorithms are efficient and generate node sets with high-quality. Related Articles | Metrics

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Different Forms of Nonlinear Schrödinger Equation and Solutions Using Split Step Fourier Method LÜ Lixiang, ZHANG Xiaoping CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2007, 24 (3): 373-377.   Abstract （724）      PDF （215KB）（2840）       Knowledge map    The positive and negative frequency expressions of quasi-monochromatic optical fields of a pulse in fiber-optic communication and the positive and negative frequency forms of Fourier transformations and nonlinear Schrödinger(NLS) equations are discussed.Especially,in the solution of pulse spectrum,the negative frequency form of NLS equation should be solved by the negative frequency form of Fourier transformation,while the positive frequency form of NLS equation is solved by the positive frequency form of Fourier transformation.An example is given using split step Fourier method. Related Articles | Metrics

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Mechanism of Acetylenic-Keton Intramolecular Cyclization Reaction Catalyzed by AuCl3 LI Anjun, ZHU Yuanqiang, SU Hong, YANG Zehong CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2017, 34 (6): 679-684.   Abstract （721）   HTML （0）    PDF （2518KB）（1477）       Knowledge map    Density functional theory with B3LYP functionals was used to study generating phenanthrene derivatives mechanism of acetylenic-keton intramolecular cyclization reaction catalyzed by AuCl3. It shows that the reaction can occur through [2+2] and [2+6] reaction pathways with and without AuCl3 catalyst. Without catalyst, energy barrier of rate determining step of [2+2] pathway is lower than that of [2+6] pathway by 32.01 kJ·mol-1. Reaction mainly occurs through [2+2] pathway. With AuCl3 catalyst, dominent reaction pathway is still [2+2] pathway with an energy barrier of rate determining step of 137.05 kJ·mol-1. Energy barrier of rate determining step of four-membered ring pathway with AuCl3 catalyst is 102.72 kJ·mol-1 lower than that of reaction without catalyst. This difference indicates that AuCl3 is an efficient catalyst which can raise reaction rate and moderate reaction condition. Reference | Related Articles | Metrics

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COMPUTING METHOD OF STOCHASTIC DIFFERENTIAL EQUATION AND IT'S APPLICATION LIU Xiao-qing, WU Sheng-Chang CHINESE JOURNAL OF COMPUTATIONAL PHYSICS    2002, 19 (1): 1-7.   Abstract （710）      PDF （288KB）（3638）       Knowledge map    Construction of discretization schemes, convergence principle, strongly convergent scheme and weakly convergent scheme for stochastic differential equations as well as computing method of jump stochastic differential equation are presented. Related partial differential equations are solved by probability method. Finally several examples in application are given. Related Articles | Metrics

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A Multi-material Five-equation-reduced Model and Artificial Compression Method for Interface Capture Chuang XUE, Xingdong LI, Wenjun SUN, Wenhua YE, Xianjue PENG Chinese Journal of Computational Physics    2021, 38 (3): 257-268.   DOI: 10.19596/j.cnki.1001-246x.8248 Abstract （699）   HTML （1083427）    PDF （8825KB）（2031）       Knowledge map    The volume fraction equations of five-equation-reduced model were studied and numerical scheme was developed in two-dimensional Eulerian frame in planar and cylindrical geometry. To capture material interfaces, Yang's slope modification of artificial compression method was adopted in MUSCL, PPM and WENO type data reconstruction processes. HLLC-HLLCM hybrid flux was applied in Godunov type scheme to avoid numerical shock instability. For multi-material Riemann problems, numerical results show that the scheme captures shock and contact discontinuities with non-oscillatory character. No numerical shock instabilities growing shows as small perturbations was adding on initial physical variables. SOD problems in cylindrical and spherical geometries and contact-type two-dimensional Riemann problem were studied. Table and Figures | Reference | Related Articles | Metrics