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25 July 2018, Volume 35 Issue 4 Previous Issue    Next Issue

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A Three-dimensional Multiple-Relaxation-Time Lattice Boltzmann Method for Whole-Speed-Range CHEN Feng, XU Aiguo, ZHANG Guangcai, JIAO Peigang 2018, 35(4): 379-387.  DOI: 10.19596/j.cnki.1001-246x.7680 Abstract ( )   HTML ( )   PDF (1731KB) ( )   A three-dimensional (3D) free-parameter multiple-relaxation-time lattice Boltzmann method for high speed compressible and low speed incompressible flows is presented. In the approach transformation matrix is constructed according to irreducible representation basis functions of SO(3) group. Equilibria of nonconserved moments are chosen so as to recover compressible Navier-Stokes equations through Chapman-Enskog analysis. Sizes of discrete velocities are flexible. Influence of model parameters on numerical stability is analyzed. Reference values of parameters are suggested. To validate performance of the model, several well-known benchmark problems ranging from 1D to 3D are simulated. Numerical results are in good agreement with analytical solutions and/or other numerical results.

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Numerical Study on Influence of Reaction Mechanisms on Reactive Shock Bubble Interaction WANG Ziang, YU Bin, HANG Haotian, ZHANG Bin, LIU Hong 2018, 35(4): 388-396.  DOI: 10.19596/j.cnki.1001-246x.7665 Abstract ( )   HTML ( )   PDF (5996KB) ( )   We solve Navier-Stokes equation with chemical source term, focusing on effect of three oxygen-hydrogen chemical reaction mechanisms on ignition, combustion efficiency and area compression ratio of reactive shock bubble interaction(RSBI). These chemical reaction mechanisms are Evans-Schexnayder(ES) model, Jachimowski(J) model, Ó Conaire(Ó) model, respectively. Results simulated with ES model show that subjected to shock wave,bubble has the largest ignition delay; the lowest balanced temperature and its ignition position is different from J model and Ó model.Dimensionless area is adopted to characterize shape of bubble under effect of shock and combustion. It shows that simulation of bubble area is closely related to chemical reaction model after stage of heat release,and J model has the highest dilation rate. In simulating combustion efficiency of long-term RSBI flow field, differences among chemical reaction models are relatively decreased. As ES model fails to reveal ignition position correctly, J model and Ó model are suitable for simulating RSBI.

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A Hybrid WENO Scheme for Resolution Optimization GUO Yuan, TIAN Qi, LIANG Xian, LI Xinliang 2018, 35(4): 397-404.  DOI: 10.19596/j.cnki.1001-246x.7664 Abstract ( )   HTML ( )   PDF (1906KB) ( )   To improve finite difference scheme, Fourier analysis is used to optimize dispersion and dissipation of WENO scheme. And optimal linear weights are given. A class of hybrid schemes is designed by combing optimized WENO schemes with monotonicity-preserving scheme. A weighted hybrid WENO scheme(H-WENO) is obtained. The scheme is tested with one-dimensional shock tube problem, Shu-Osher problem, two-dimensional Mach reflection problem and R-T instability problem. It shows that the scheme has strong ability to capture shock wave and high resolution for small scale wave structure, which is improved obviously compared with original WENO scheme.

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Lattice Boltzmann Simulation of Double Diffusive Natural Convection in an Enclosure with Soret and Dufour Effects WANG Jun, LOU Qin, XU Hongtao, CHEN Jian, YANG Mo 2018, 35(4): 405-412.  DOI: 10.19596/j.cnki.1001-246x.7658 Abstract ( )   HTML ( )   PDF (1825KB) ( )   We adopt lattice Boltzmann method to investigate double diffusive natural convection around a heated cylinder in an enclosure with Soret and Dufour effects. The inner heated cylinder is located at center of a square enclosure and four surrounding walls are assumed with low temperature and concentration. In the model, distributions of velocity, temperature and concentration are solved with three independent LBGK equations which are combined into a coupled equation through Boussinesq approximation. Influences of Soret number and Dufour number on double diffusive natural convection are analyzed. Streamlines, isotherms, isoconcentrations, average Nusselt and Sherwood numbers around heated cylinder in enclosure are presented. It shows that Soret and Dufour effects have significant influence on double diffusive natural convection.

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A Strang-type Alternating Segment Domain Decomposition Method for Two-dimensional Parabolic Equations ZHANG Shouhui, LIANG Dong 2018, 35(4): 413-428.  Abstract ( )   HTML ( )   PDF (1044KB) ( )   A Strang-type alternating segment domain decomposition method for 2-D parabolic problems is proposed. The domain can be divided into non-overlapping multi-block sub-domains by the idea of alternating segments. Strang-type splitting technique reduces complexity of the solving of the high dimensional problems by a series of one-dimensional ones. The method is proved to be unconditionally stable and truncation error is analyzed. Numerical experiments show that convergence rates in time and space are both second order.

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Numerical Simulation of Fission Neutron Angular Correlation Distributions ZHU Jianyu, HUANG Meng 2018, 35(4): 429-436.  DOI: 10.19596/j.cnki.1001-246x.7663 Abstract ( )   HTML ( )   PDF (2487KB) ( )   For numerical simulation of spontaneous fission neutron source energy, neutron multiplicity and neutron angular correlation distribution, a NESF numerical simulation program is developed to provide fission neutron multiplicity, energy, angular distribution and other parameters on basis of fission process. The program is integrated into existing neutron transport software. This report focuses on background, physical basis, and process of the program, as well as numerical simulation correlated to neutron angular correlation distribution characteristics and nuclear component characteristics.

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A Magnetic Field Divergence Cleaning Method in MHD Numerical Simulations YANG Yun 2018, 35(4): 437-442.  DOI: 10.19596/j.cnki.1001-246x.7688 Abstract ( )   HTML ( )   PDF (3549KB) ( )   We make use of characteristics of CESE method(in CESE method, conservative variables as well as their spatial derivatives are regarded as independent marching quantity and solution points are on boundary of every control volume) and give a new method to clean magnetic field divergence by using the least-squares method. We also explore the influence of the weights of magnetic field divergence constrained equation on the results, by comparison, we found that when the weight of the equation is 1, the magnetic field divergence can be decreased efficienty.

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Parallel Computing of Multipoint-Base-Excited Harmonic Response with PANDA Platform YU Chenyang, FAN Xuanhua, WANG Keying, XIAO Shifu 2018, 35(4): 443-450.  DOI: 10.19596/j.cnki.1001-246x.7708 Abstract ( )   HTML ( )   PDF (2083KB) ( )   Based on self-developped parallel software platform PANDA, algorithm design and parallel implementation of multipoint-base-excited harmonic response were carried out via modal superposition method. Corresponding parallel solution module was constructed, rightness of which is validated by comparisons with commercial FE software. Parallel module was successfully applied to harmonic response analysis of SG facility. An effective parallel solution of extensive computing scale up to 1.188 billion DOFs was achieved. It shows that parallel solution module is suitable to large-scale refined harmonic response analysis of complex equipments, behaving a strong parallel computing scalability up to thousands of CPU processors, and going far beyond the scale of commercial FE software.

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Standards for Grid and Zone in Simulation of Flow in 5×5 Pins Assembly LIU Jian, CHEN Jun, LI Jian, WANG Shiqing 2018, 35(4): 451-457.  DOI: 10.19596/j.cnki.1001-246x.7660 Abstract ( )   HTML ( )   PDF (4680KB) ( )   To obtain reasonable scales and grid requirements of computational zone, water flow in 5×5 fuel pins assembly was simulated adopting incompressible N-S equations, standard k-ε turbulent model and SIMPLE algorithm. By comparing pressure drop, velocity and its vertical component at different planes perpendicular to fuel pins, with relative error smaller than 5%, conclusions were obtained. Length of inlet part and outlet part of computational domain should be about 2.0 times and 2.3-2.8 times of space between two spacer. Polyhedral mesh should be adopted and its scale should be smaller than 0.35 mm in zone between spacer as smooth pin zone adopt structured grid with 0.3 mm-0.5 mm dimension.

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Dynamical Behavior Analysis of a Class of 4D Memristive Chaotic System LIU Di, YANG Fangyan, ZHOU Guopeng, LI Qingdu, LIAO Xiaoxin 2018, 35(4): 458-468.  DOI: 10.19596/j.cnki.1001-246x.7678 Abstract ( )   HTML ( )   PDF (15059KB) ( )   Dynamical behavior of a class of 4D memristive chaotic circuits was discussed, and attracting domain of multi-stability was studied. In order to guarantee efficiency and accuracy of calculation results, CPU+GPU large-scale computing power were introduced and more than 128 decimal places of precision GMP library and MPFR library were applied to calculate domain of corresponding attractor. Finally, existence of hyperchaos was proved by using method of topological horseshoe theory and constructing memristive analog circuit.

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Spectral Properties of Excited States of MgI Molecule Based on Multi-reference Configuration Interaction Method WU Donglan, TAN Bin, WEN Yufeng, ZENG Xuefeng, XIE Andong 2018, 35(4): 469-474.  DOI: 10.19596/j.cnki.1001-246x.7694 Abstract ( )   HTML ( )   PDF (1371KB) ( )   Potential energy curves and dipole moments of five bound states are computed by high-level multi-reference configuration interaction method with all-electron aug-cc-pwCV5Z+DK for Mg atom and aug-cc-pV5Z-PP for I atom. To obtain high precise spectroscopic properties, Davidson modification, core valence correlation and relativistic correction are introduced. Based on PECs of 5 bound states, accurate spectroscopic constants, vibration levels and molecular constants of bound states are obtained by solving radial Schrödinger equation. Compared with recent theoretical calculation our results are closer to experimental datum. It shows that high precision calculation method and correlation correction are necessary for analysis of spectral properties. It provides support for further research on spectroscopic and transition characters of higher excited states of MgI molecule.

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Defect Location Effect on Tensile Behavior of Graphene MA Jiangjiang, LI Kexun, ZHOU Bicheng, GU Jianyu, JIA Kun 2018, 35(4): 475-480.  DOI: 10.19596/j.cnki.1001-246x.7704 Abstract ( )   HTML ( )   PDF (13382KB) ( )   Molecular dynamic (MD) simulations were performed to simulate stretching process of graphene containing defect in which AIREBO potential is used to describe interactions of atoms. We investigated defect location effect on tensile behavior of graphene. It shows that defect location has different influence on fracture process of graphene. Distance to boundary and arrangement of defect have great effect on mechanical stability of graphene. It suggests that mechanical property of graphene can be improved through location control of defect.

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A study on Physical Properties of Mn-Doped (ZnSe)12 Clusters XIE Jianming, CHEN Hongxia, ZHUANG Guoce 2018, 35(4): 481-486.  DOI: 10.19596/j.cnki.1001-246x.7651 Abstract ( )   HTML ( )   PDF (4641KB) ( )   Structure, electronic and magnetic properties of (ZnSe)12 clusters doped with one or two Mn atoms were studied with a first-principles method. Substitutional, exohedral, and endohedral doping are considered. Substitutional isomers are found most favorable for both monodoped and bidoped clusters. Magnetic moment is mainly contributed by 3d component of Mn atom, while 4s and 4p orbitals also have certain contributions. Due to hybridization interaction, a small magnetic moment is induced in nearest neighboring Se and Zn atoms. We demonstrate that endohedral bidoped (ZnTe)12 clusters favor ferromagnetic state, which has potential applications in nanoscale quantum devices.

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Density Functional Theory Calculations of Ga Doped δ-Pu LI Dawei, GAO Yunliang, ZHU Yuanjiang, LI Jinping 2018, 35(4): 487-493.  DOI: 10.19596/j.cnki.1001-246x.7673 Abstract ( )   HTML ( )   PDF (3673KB) ( )   As a high-temperature phase of Pu, δ-Pu doped with little Ga can stay to room temperature. Crystal structure and electronic structure of systems with different contents of Ga are calculated with density functional theory (DFT) method. Calculations mainly include lattice constant, density, formation energy, density of states(DOS), electron density and Mulliken population. It shows that within studied doping scope, lattice constant of systems decrease and density of systems increase with increase of content of Ga, while stability of system with 6.25% content of Ga is superior to that with 3.125% and 12.5% content of Ga. Ga-doping enhanced locality and strengthens bonding ability of electrons, which, to some degree, reveals electronic mechanism of Ga stabilizing δ-Pu. Character of Pu-Ga bond is metallic state, and interaction is mainly contributed by Pu 7s, 6p, 6d and Ga 4s, 4p orbital electrons. While interaction is relatively weak, doped systems maintain fine mechanical properties and machining performance. Contribution of Ga to stability of δ-Pu lies mainly in its improvement on bonding performance of Pu, instead of its immediate bonding effect with Pu.

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Investigation on Multiferroicity in Spinel Oxide CoCr2O4 LIU Jiahong, DU An, QI Yan 2018, 35(4): 494-504.  DOI: 10.19596/j.cnki.1001-246x.7675 Abstract ( )   HTML ( )   PDF (1735KB) ( )   To understand fantastic multiferroicity of CoCr2O4, a Heisenberg spin model on three-dimensional spinel lattice was constructed. In the model, we considered multiple magnetic interactions including nearest-neighbor A-A, A-B, B-B couplings as well as next-nearest-neighbor interaction among B sites. Monte Carlo simulation is employed to obtain magnetoelectric quantities. Influences of exchange couplings on magnetoelectric behaviors are emphatically investigated under rotation of magnetic field. It is found that macroscopic magnetization and polarization stem mainly from contributions of B1 ions. With varying exchange couplings of A-A interaction and next-nearest-neighboring B-B interaction among B-site ions, B-site ions exhibit prominent magnetoelectric responses, while A-site ions remain unchanged. It indicates distinct differences between symmetry and magnetic interaction environment for A-site and B-site ions in spinel lattice.