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25 September 2010, Volume 27 Issue 5 Previous Issue    Next Issue

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A Two-dimensional Monotonicity-and Conservation-preserving Interpolation Operator MA Libin, HU Xiaoyan, MO Zeyao 2010, 27(5): 633-640.  Abstract ( )   PDF (479KB) ( )   We propose a two-dimensional(2D) monotonicity-and conservation-preserving interpolation operator based on a one-dimensional monotonicity-and conservation-preserving interpolation operator.With several numerical examples we conclude that our interpolation operator is effective.Furthermore,we take it as a refinement interpolation operator in a structured adaptive mesh refinement(SAMR) algorithm to solve numerical examples governed by 2D Euler equation.Results show that our method is effective in SAMR.

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A Integrated Gradient Scheme for Preservation of Symmetry YONG Heng, LIAN Zhiqiang, ZENG Qinghong, YUAN Guoxing, WANG Zheng 2010, 27(5): 641-648.  Abstract ( )   PDF (372KB) ( )   An integrated gradient total symmetry-preserving(IGTSP) scheme for momentum equations of Lagrangian hydrodynamics in cylindrical coordinates is presented.The scheme inherits advantages of both IGT and IGA schemes,that is,the scheme not only overcomes nonsymmetry of the IGT scheme but also has a momentum conservation error of order O(h),one order higher than that of IGA scheme.A number of numerical examples are tested to demonstrate advantages of IGTSP scheme.

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A 3D Constrained Unstructured Mesh Generation Method with VBATM and Steiner Points Perturbation WANG Shengxi, SONG Songhe, ZOU Zhengping 2010, 27(5): 649-657.  Abstract ( )   PDF (500KB) ( )   A constrained boundary recovery algorithm for 3D unstructured meshes which combines vector boundary advancing triangulation method(VBATM) with Steiner point perturbation is presented.From conforming mesh,constrained edges and faces could be recovered by Steiner point perturbation and VBATM to reconstruct triangulation on constrained faces.The tetrahedral-eating method can be used to get rid of Steiner points as many as possible.Different from existing methods,the algorithm does not need edges/faces swapping(flip) method and side compress method.Convergence and stability of the method are theoretically studied.Numerical examples are provided to illustrate effectiveness of the method.

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Closing Relations in Two-step Eulerian Method for Multifluid Dynamics LIANG Xianhong, LI Zheng, HE Changjiang, LIU Chao 2010, 27(5): 658-664.  Abstract ( )   PDF (272KB) ( )   We describe a problem that the multifluid dynamic equations are not closed.To solve equations,they must be closed.Existing closing relations are analyzed and an adaptive closing relation method according to sound velocity is given.Numerical example shows that pressure relaxation is also important for pressure equalization in mixed cells.

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Investigation on Cross-flow Instabilities in Swept-wing Boundary Layers with Linear Parabolized Stability Equations ZUO Suihan, YANG Yong, LI Dong 2010, 27(5): 665-670.  Abstract ( )   PDF (333KB) ( )   Linear parabolized stability equations(LPSE) considering model curvature are solved with finite difference method.Stationary cross-flow instabilities in boundary layers of an infinite swept-wing are analyzed.LPSE and experimental results are compared.It is shown that at early development of stationary cross-flow disturbances,LPSE simulates flow structure and disturbance profiles well and predicts the N-factors accurately.When disturbances are amplified enough,high order terms can not be omitted and linearization assumption of LPSE is no longer suitable.Moreover,effects of model curvature and boundary layer non-parallelism are investigated.It shows that curvature and non-parallel terms have significant effects on stability analysis of stationary cross-flow instabilities on a swept-wing,and the effects are independent of Reynolds numbers.In the model investigated,inclusion of curvature has a stabilizing effect and non-parallelism shows destabilizing effects on disturbances.

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High Resolution Entropy Stable Schemes for Hyperbolic Conservation Laws LUO Li, FENG Jianhu, TANG Xiaojuan, XIANG Liang 2010, 27(5): 671-678.  Abstract ( )   PDF (348KB) ( )   Entropy stable schemes based on physical concepts guarantee the dissipation of total entropy.They are unnecessarily entropy-fixed and effectively avoid unphysical phenomena such as expansion shock and negative pressure.By inserting limiters and using high order reconstructions at cell interfaces,a high resolution entropy stable scheme is proposed.Several numerical experiments demonstrate that the scheme is robust,accurate and essentially non-oscillations.

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Numerical Simulation of Transient Viscoelastic Flows Using SPH Method YANG Bo, OUYANG Jie 2010, 27(5): 679-684.  Abstract ( )   PDF (278KB) ( )   Smoothed particle hydrodynamics(SPH) method is applied to simulate transient viscoelastic flows.The method for viscoelastic flows is verified by comparing numerical solution with analytical solution of an Oldroyd-B fluid in a start-up Couette flow.An Oldroyd-B fluid in a lid-driven cavity is simulated by the method.In addition,a new treatment of solid wall boundaries is presented to prevent particles penetrating solid walls and improve numerical accuracy.It shows that SPH method is valid and stable in simulation of viscoelastic flows.

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An Uncoupled Method with Dual Time-step for Chemical Nonequilibrium Flows WANG Hongbo, SUN Mingbo, LIANG Jianhan, WANG Zhenguo 2010, 27(5): 685-691.  Abstract ( )   PDF (405KB) ( )   An uncoupled method based on an implicit dual time-step approach for nonequilibrium flows is developed.Flow and reaction are separated by using operator-splitting method.Flow equations are solved by a dual time-step approach and source equations are solved by 2nd order trapezoidal formulas.A source-eliminating method is designed to remove error imposed to the solution by chemical source,which is very effective to assure time precision of flow-solving.Analysis and computations suggest that the method maintains efficiency of dual time-step approach as well as precision of unsteady computational results.

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Finite Element Simulation of Heterogeneous Reservoir with Full Permeability Tensor LI Yajun, YAO Jun, HUANG Zhaoqin, ZHANG Kai 2010, 27(5): 692-698.  Abstract ( )   PDF (347KB) ( )   Mathematical model with full tensorial permeability and mixed boundaries is presented to simulate single phase flow in heterogeneous reservoirs.A finite element method based on variational principle is proposed to solve the model.Fluid flows in homogeneous and heterogeneous reservoirs are simulated.It demonstrates that the finite element method is reliable and precise in determining flow behavior in heterogeneous reservoirs.It provides an important theoretical basis for detailed reservoir numerical simulation.

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Nonlinear Heat Conduction Equation Solved with Lattice Boltzmann Method ZHANG Donghui, LIU Fanggui, ZHANG Jincun, RUI Xiaofang 2010, 27(5): 699-704.  Abstract ( )   PDF (275KB) ( )   Lattice Boltzmann method is employed to study nonlinear heat conduction problems.A kind of lattice Boltzmann model is derived in details and multi-scale algorithm and macroscopic quantity are selected.It is proposed to solve transient responses of nonlinear heat conduction problems.The relation between heat conductivity and temperature meets the multi-polynomial function.Different parameters are considered to verify feasibility of the proposed method.Simulation results are illustrated with comparison in linear case.

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Iterative Method for Continuation of Three-component Magnetic Field YAN Hui, XIAO Changhan, ZHANG Zhaoyang, ZHU Xingle 2010, 27(5): 705-710.  Abstract ( )   PDF (395KB) ( )   An iterative continuation method for three-component magnetic field is presented.It aims at downward continuation of three-component magnetic field.The fields on those points with same horizontal coordinates are related by differential calculus.As divergence and rotation of three-component magnetic field are taken into consideration,vertical derivatives can be described with horizontal derivatives.As three-component magnetic field on an upper plane is known,magnetic fields on lower planes can be computed with an iterative procedure.Efficiency and accuracy are illustrated by applications.

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Substructure Fast Multipole Boundary Element Approach for Acoustic Performance Prediction of Silencers CIU Xiaobing, JI Zhenlin 2010, 27(5): 711-716.  Abstract ( )   PDF (356KB) ( )   A substructure FMBEM approach is developed for multi-domain sound field computations.The basic approach and process as well as advantages and disadvantages are introduced.Transmission loss of expansion chamber with extended inlet tube is calculated by using substructure FMBEM and conventional boundary element method(CBEM).Availability and accuracy of the approach are validated with experimental result.It indicates that,compared to the CBEM,substructure FMBEM reduces computational time and computational complexity obviously as the number of nodes is increased.

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Super-high Energy Neutrons Produced by Neutron Collision LI Shu, TIAN Dongfeng, DENG Li 2010, 27(5): 717-721.  Abstract ( )   PDF (230KB) ( )   Relationship between super-high energy neutrons and collisions is derived.Monte Carlo method is used to decide speed of neutrons after collision.A code applicable to nonlinear neutron transport problem is developed to simulate neutron collision and transportation.Numerical calculation indicates that production rate of super-high energy neutrons is in linear relationship with the square of neutron source intensity.

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Global Variance Reduction Method for Monte Carlo Particle Transport Problemes XU Haiyan, HUANG Zhengfeng, CAI Shaohui 2010, 27(5): 722-732.  Abstract ( )   PDF (647KB) ( )   A global variance reduction method is described.The method is based on a modified transport problem that can be solved by analog Monte Carlo with zero variance.It is developed by breaking up the whole into parts and coupling Monte Carlo method with discrete ordinates method and using approximate importance function to guide Monte Carlo simulation.Performance of the method for a one-dimensional sphere transport problem is demonstrated.The method is shown to produce lower variances globally compared to analog Monte Carlo.

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Time Station Importance Sampling Method for Flux Field Calculation of Time-dependent Problem WANG Ruihong, JI Zhicheng, JIANG Song, HUANG Zhengfeng, PEI Lucheng 2010, 27(5): 733-739.  Abstract ( )   PDF (442KB) ( )   Flux field calculation in time-dependent problems with Monte Carlo method and associated particles transportation equation are described.The random walk principle of time station sampling(TSS) method in dynamic system is introduced.A time station importance sampling(TSIS) method is developed and applied to decrease statistical fluctuation in global flux field calculation.Alternative importance function and its unbiased weight of modification are investigated.Numerical results and analyses on methods in specific model are given.The time station importance sampling(TSIS) biased method can be used to control statistical variance of global fine mesh flux adaptively in a same level.

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Monte Carlo Simulation of Gamma Ray Transport in Non-uniform Atmosphere TAO Yinglong, ZHU Jinhui, WANG Jianguo, NIU Shengli, FAN Ruyu 2010, 27(5): 740-744.  Abstract ( )   PDF (241KB) ( )   The atmosphere is a kind of non-uniform media,whose density drops rapidly with the increase of height.In order to simulate transport of gamma ray in high-altitude atmosphere,the media is divided into many uniform layers with different densities.To eliminate error,the number of layers should be as many as possible,which results in a large amount of computation.We propose a method without layering.It samples mass distance to replace step length of particles.The results agree well with those calculated directly by MCNP code.The method increases speed of computation considerably.

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A Semi-microscopic Proton Optical Potential HU Zehua, SUN Weili, WANG Jia, ZHANG Benai 2010, 27(5): 745-751.  Abstract ( )   PDF (376KB) ( )   A semi-microscopic proton optical potential with parameters is constructed for analyzing elastic scattering data.It's real part is given by a folding model incorporated with one-body density matrix of shell model with Woods-Saxon potential,and the imaginary part is taken consistently with that of Koning-Delaroche(K-D) global optical potential.Potential parameters are obtained by fitting proton elastic scattering data up to 200 MeV in a range of mass number A=28~90.Compared with measurements of elastic scattering angular distributions and analyzing powers it is overall better than those of K-D global optical potential.

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First-principles Study of Electronic Structure and Optical Properties of A-La2O3 LIU Qijun, LIU Zhengtang, FENG Liping 2010, 27(5): 752-758.  Abstract ( )   PDF (344KB) ( )   Electronic structure and optical properties of A-La2O3 are investigated with plane waves ultrasoft pseudopotential technique in density functional theory (DFT).Calculated results show that A-La2O3 is indirect oxide with a band gap of 3.72 eV.Valence bands of A-La2O3 are composed of La-5s,La-5p,La-6s,O-2s,O-2p and the conduction bands are mainly composed of La-5d.With band gap correction,optical linear response functions of A-La2O3 as a function of photon energy are obtained including complex dielectric function,complex of refractive,absorption coefficients,reflectivity,loss function and complex conductivity function in(100) and(001) directions.It shows that A-La2O3 shows optical anisotropy in polarization directions(100) and(001),and A-La2O3 is high transmission from near-ultraviolet to infrared,which offers a theoretical basis for applications.

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First-principles Study of Structural Phase Transformation and Electronic Structure of ZnO Under High Pressures HAO Junhua, WU Zhiqiang, WANG Zheng, JIN Qinghua, LI Baohui, DING Datong 2010, 27(5): 759-764.  Abstract ( )   PDF (325KB) ( )   Equation of state and phase transformation of ZnO in wurtzite structure and NaCl structure under high pressures are studied using density function theory(DFT) formalism.We analyze structural properties,including lattice constant,electronic density of states and band gap.The results are in good agreement with experimental and other theoretical results.It is found that the calculated phase trasformation pressure of metallic oxides using local density approximation(LDA) is generally higher than experimental results.Calculated results using generalized gradient approximation(GGA) are in good agreement with experiments.

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Stable Structures of Binary Molecular Cluster of 3(H2O)4 HU Weijun, YANG Hua, MENG Xianmei, SUN Ping 2010, 27(5): 765-770.  Abstract ( )   PDF (393KB) ( )   An empirical potential of binary molecular clusters of (NH3)m(H2O)4 is proposed.Stable model structures of NH3(H2O)4 are optimized by using a fast molecular dynamics algorithm.The optimal structures are refined by using conventional ab initio optimization method.Optimization and frequency calculations are carried out at different levels of density functional theory (DFT/B3LYP) and Mller-Plesset second-order perturbation method(MP2) with 6-311++G** basis set.It is found that stable model structures remain the minima at B3LYP and MP2 levels.12 new ab initio stable isomers of NH3(H2O)4,including the second and third ones are obtained.The results show that there is no inevitable relevancy between stability and dipole moment,and the number of hydrogen bonds of isomers.

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Modeling and Simulation of Double Base Epilayer 4H-SiC BJTs ZHANG Qian, ZHANG Yuming, ZHANG Yimen 2010, 27(5): 771-778.  Abstract ( )   PDF (299KB) ( )   With characteristics of 4H-SiC,a double base epilayer 4H-SiC bipolar junction transistors(BJTs) is investigated.By analyzing build-in electric field in the base region and the base transit time,the device is numerically calculated in two-dimensional models according to orthogonal experiments.A mean range analysis is made to find optimized structure of 4H-SiC BJTs.It shows that common emitter current gain with negative temperature coefficient is about 72 and it remains high in a wide range of collector current.

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Novel Chemical Sensor of NO2:Silicon Carbide Nanotubes DING Ruixue, YANG Yintang, LIU Lianxi 2010, 27(5): 779-784.  Abstract ( )   PDF (295KB) ( )   Structure and electronic properties of silicon carbide nanotube(SiCNT) with and without adsorption of NO2 are calculated with CASTEP package based on density functional theory.A stable adsorption between nanotube and gas molecule is formed and conductivity of the SiCNT is improved obviously.It is shown that SiCNT is a potential candidate for gas sensors.It is expected to provide a useful guidance in developing SiCNT-based sensors for NO2 molecules.

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Effects of Molecular Orientation and Laser Intensity in Non-sequential Double Ionization WEI Yana, TIAN Gang, LI Yan, YANG Shiping 2010, 27(5): 785-790.  Abstract ( )   PDF (336KB) ( )   In semiclassical rescattering model,momentum distribution of recoil ions,momentum correlation of two ejected electrons and ionized energy of tunnelled electron are calculated as molecular orientation is parallel or perpendicular to the linearly polarized field.It indicates that molecular orientation and laser intensity have strong impacts on non-sequential double ionization.