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25 July 2009, Volume 26 Issue 4 Previous Issue    Next Issue

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Progress in Numerical Methods for Radiation Diffusion Equations YUAN Guangwei, HANG Xudeng, SHENG Zhiqiang, YUE Jingyan 2009, 26(4): 475-500.  Abstract ( )   PDF (1809KB) ( )   Radiative transfer in fluid flow of radiation hydrodynamics is studied.Kinetic laws under radiation condition are investigated.Practical radiation hydrodynamics process is complicated,and numerical simulation is one of primary research means.Splitting methods are often used in numerical simulation,in which fluid motion and radiation are computed separately.We discuss computational problems in radiation diffusion calculations.Diffusion schemes and nonlinear iterative methods on severely distorted meshes are studied.A brief introduction on research progress is given.

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RKCVDFEM for One-dimensional Hyperbolic Conservation Laws CHEN Dawei, YU Xijun 2009, 26(4): 501-509.  Abstract ( )   PDF (349KB) ( )   Runge-Kutta control volume discontinuous finite element method (RKCVDFEM) is proposed to solve numerically hyperbolic conservation laws,in which space discretization is based on control volume finite element method (CVFEM) while time discretization is based on a second order accurate TVB Runge-Kutta technique.Piecewise linear function space is chosen as finite element space.The scheme is total variation bounded (TVB) and is formally second order accurate in space and time.Numerical examples show that numerical solution converges to the entropy solution,and order of convergence is optimal for smooth solution.Compared with numerical results of Runge-Kutta discontinuous Galerkin method (RKDGM) those of RKCVDFEM are better.

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Shock Limiter in Front Tracking Method WANG Donghong, ZHAO Ning, LIU Jianming 2009, 26(4): 510-516.  Abstract ( )   PDF (326KB) ( )   Riemann problems are constructed at interface in front tracking (FT) method for multi-fluid flows to study application of shock limiter.In gas-gas and gas-water problems,shock limiter parameter is selected about 0.3 considering average conservation error,L1 error and strength of the shock.It is indicated that in order to obtain better solutions the back shock wave should be selected as an original state for Riemann problems at the interface as a shock is close to a material interface.

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A Cartesian Mesh Algorithm for Supersonic Flows Around Arbitrary Moving Bodies WANG Qiang, HU Xiangyu, JIANG Zonglin 2009, 26(4): 517-526.  Abstract ( )   PDF (683KB) ( )   A Cartesian mesh algorithm is developed for numerical solution of supersonic flows with arbitrarily complex and moving solid boundaries.The method defines and tracks fluid-solid interfaces with a level set function. Fluid-solid boundary condition is dealed with a ghost cell technique and is calculated separately in normal and tangential directions.The method proposed is simple,robust,and can work with high-order finite difference schemes.To validate the scheme,one-and two-dimensional numerical examples involving static or moving boundaries are included.

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Delaunay Triangulation for Internal Node Generation in Frontal Approach and Application CHEN Yan, CAO Shuliang, LIANG Kaihong, ZHU Baoshan 2009, 26(4): 527-533.  Abstract ( )   PDF (513KB) ( )   A mixed unstructured mesh generation method is proposed for complicated computational domains.Delaunay triangulation is applied based on initial meshes generated by frontal approach.It indicates that the mixed method shows good geometrical features and high efficiency.Characteristic based split scheme is applied to flows around a square cylinder in a channel with unstructured meshes generated by mixed method.

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Three-dimensional Massively Parallel Numerical Simulation of Kerosene-fueled Scramjet YANG Shunhua, LE Jialing, ZHAO Huiyong, ZHENG Zhonghua 2009, 26(4): 534-540.  Abstract ( )   PDF (418KB) ( )   Massively parallel numerical simulation of a kerosene-fueled scramjet on national MPP computer with 1024 CPUs is presented.A self-developed software AHL3D is employed.Reynolds averaged N-S equations are adopted in governing equations.Inviscid flux is computed with Steger-Warming flux-splitting scheme.Turbulent effects are studied in a k-ω two-equation turbulence model.Kerosene is replaced by a simple surrogated fuel of n-decane.Computed wall pressure along combustor exhibits good agreement with measured data.Computation shows that cavity provides main ignition zone and flame holder,and recirculation zone resulting from fuel injection contributes to flame stability.It indicates that the AHL3D code and methodologies can be used to simulate complicated flow patterns in kerosene-fueled scramjets.

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Numerical Study on Gain Distribution in COIL: Flow Rate Ratio of Primary and Secondary Flow LV Junming, WANG Chun, JIANG Zonglin 2009, 26(4): 541-547.  Abstract ( )   PDF (518KB) ( )   Three-dimensional CFD technology is applied in a RADICL model by solving laminar Navier-Stokes equations and transportation equations to study iodine molecule dissociation rate,iodine atom pumping rate,singlet oxygen yield rate and small signal gain at different flow rate ratio of primary and secondary flow.It is found that an appropriate flow rate ratio plays an important role in spatial distribution of the small signal gain.Rich or poor oxygen conditions go against with a proper gain.

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Initial Smoothing Length and Space Between Particles in SPH Method for Numerical Simulation of High-speed Impacts XU Jinzhong, TANG Wenhui 2009, 26(4): 548-552.  Abstract ( )   PDF (309KB) ( )   High-speed impact problems are simulated with smoothed particle hydrodynamics method.Initial smoothing length and nonconforming space between particles in simulation are analyzed.A modified smoothing length approach is put forward.With increase of initial smoothing length, projectile rigidity decreases gradually.A rational range of initial smoothing length is d0< h0≤ 1.5d0.With decrease of space between particles,rigidity of material decreases.With XSPH correction on velocity of a particle,results by nonconforming space between particles agree well with those from identical particle distribution.

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Reproducing Kernel Particle Method in Smoothed Particle Hydrodynamics YIN Jianwei, MA Zhibo 2009, 26(4): 553-558.  Abstract ( )   PDF (346KB) ( )   Kernel functions approximate physical quantities in smoothed particle hydrodynamics (SPH) method.However,approximation accuracy decreases near boundaries.By reconstruction of a kernel with correcting function,reproducing kernel particle method (RKPM) improves approximation accuracy and computational stability at internal or boundary points.Though correction is proposed to approximate functions accurately,it also benefits in approximation of derivatives.

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Ballistic Performance of Long Rods: Material Properties LOU Jianfeng, HE Changjiang, ZHU Jianshi, WANG Zheng 2009, 26(4): 559-563.  Abstract ( )   PDF (360KB) ( )   Material properties are investigated on ballistic performance of tungsten-alloy rods with two-dimensional numerical simulations by program LS-DYNA.In an elastic-plastic hydrodynamic material model,primary parameters of the rod includes failure strain,yield stress and shear modulus,etc.Penetration is studied through simulation of a tungsten-alloy rod impacting on a semi-infinite aluminum-alloy target.It is shown that failure strain shows dominant effect on penetration. Numerical simulations of penetration within impact velocity regime ranging from 785 m/s to 1 924 m/s are performed.Numerical results are in good agreement with experimental data.

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Efficient Calculation of 3D Frequency-domain Green Functions YAO Xiongliang, SUN Shili, ZHANG Aman 2009, 26(4): 564-568.  Abstract ( )   PDF (266KB) ( )   We introduce Gaussian quadrature into calculation of frequency-domain Green functions and their partial derivatives.Compared with referenced methods the method proposed simplifies compution,reduces zoning and improves computing efficiency with sufficient accuracy.

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Fast Computation of Electromagnetic Scattering by Vehicle Above Ground ZHAO Xunwang, LIANG Changhong, LIANG Le 2009, 26(4): 569-573.  Abstract ( )   PDF (300KB) ( )   To study electromagnetic scattering by vehicle above ground,a half-space multilevel fast multipole algorithm (MLFMA) is proposed.Near terms in the MLFMA are evaluated by rigorous half-space dyadic Green functions.Far MLFMA interactions employ an approximate dyadic Green function via a direct-radiation term plus a single real image.The real image method leads to fast and convenient computation compared with the discrete complex image method (DCIM).It also results in less memory requirement and CPU time.Finally,bistatic radar cross sections are shown for a realistic 3D car model over lossy ground.

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Layer-oriented Integration Arithmetic for Conformal Perfectly Matched Layer ZHANG Yongjie, SUN Qin 2009, 26(4): 574-578.  Abstract ( )   PDF (269KB) ( )   We propose a layer-oriented integration arithmetic for conformal perfectly matched layer (CPML).It reduces number of element and computational scale by superposing multilayer integration to monolayer integration.To retain geometrical and material information of multilayer elements we mesh CPML by multilayer elements and calculate element matrixes by monolayer integration.Numerical examples show that layer-oriented integration CPML is a reliable and high-efficient absorbing boundary condition.

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EPR Spectra of CdCl2:Ni2+ Crystals:High-order Perturbation and Complete Diagonalization ZHANG Jinping, CHEN Taihong, DAI Wei, LAN Xiaogang, YU Fei 2009, 26(4): 579-585.  Abstract ( )   PDF (385KB) ( )   Local structure,optical absorption spectra and electron paramagnetic resonance (EPR) spectra of CdCl2:Ni2+ crystal are calculated in a semi-SCF d-orbit wave functions model for free Ni2+ ions and a point-charge-dipole model.A complete diagonalization procedure (CDP) and high-order perturbation formulas are used.Results of two methods are compared.

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Detailed Monte Carlo Simulation of Low Energy Electron Backscattering from Solids ZHUO Jun, NIU Shengli, HUANG Liuxing, ZHU Jinhui 2009, 26(4): 586-590.  Abstract ( )   PDF (271KB) ( )   Backscattering coefficients of low energy electron beams(from 100 eV to(10 000) eV) impinging on solids(Au,Si and Al) are simulated with detailed Monte Carlo code in which all interaction experienced by single electron are simulated in chronological succession.Mott cross-section and atomic generalized-oscillator-strength model within Born approximation are used to calculate elastic and inelastic scatterings in solid,respectively.Compared with various Monte Carlo codes it is concluded that detailed Monte Carlo code provided better agreement with experimental results at electron energies less than 10 keV.

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GEANT4-Based Simulation on Shielding and Radiation Effects of SPE Protons in Semiconductors LU Wei, WANG Tongquan, WANG Shangwu, CHEN Dayi, WANG Xinggong 2009, 26(4): 591-596.  Abstract ( )   PDF (336KB) ( )   We simulate radiation effects of solar cosmic protons on spacecraft and satellites with a Monte Carlo software GEANT4.Damage induced by proton irradiation and shielding of Al layer are calculated.Linear energy transfer and range in materials agree well with referenced data. Energy deposited in incident direction shows a Bragg curve and nonelastic interactions show important impact.In Si recoil atoms are mainly distributed along incident proton trajectory and isolated recoils distribute along lateral direction with lower concentration. Al shielding layer shows a shielding on high energetic protons.Shielding is hardly changed as layer thickness is larger than 10mm.On the contrary,secondary production increases obviously.

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Monte Carlo Simulation of Nematic Liquid Crystals YANG Peipei, LIU Hong, LIU Hong 2009, 26(4): 597-602.  Abstract ( )   PDF (312KB) ( )   With Monte Carlo simulation,we investigate phase transition of rod-like liquid crystals.Disciplinarian of specific heat with temperature is obtained. The peak in specific heat illustrates temperature of phase transition.Relations between order parameters and temperature are obtained.Phase diagram with different molecular structure parameters is plotted.It shows that as lengths of short rods are equal no biaxial phase exists.

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Suppression of Zero-order Term in Digital Holography Based on Hilbert-Huang Transform CHAI Xiaodong, LI Xiaohui 2009, 26(4): 603-608.  Abstract ( )   PDF (477KB) ( )   A zero-order term suppression method for digital holography with Hilbert-Huang transform is proposed.Two-dimensional hologram data are changed into one-dimensional data.The first order of intrinsic mode functions containing high frequency of hologram is obtained by Hilbert-Huang transform through empirical mode decomposition.The second order of intrinsic mode functions containing direct current component of hologram is obtained similarly.Experiments show that reconstructed image of the first order of intrinsic mode functions represents conjugate image with suppressed zero-order term,and the second order of intrinsic mode functions represent the zero-order term.The proposed method preserves effectively information of original complex-wave and shows advantage in computational speed since it decomposes empirical mode decomposition once and obtains suppressed zero-order term in space frequency field well.

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Configuration and Stability of TiO2-rutile Doped with VB Metal Ions: Molecular Dvnamics Simulation PAN Haibo, ZHANG Lipen, HUANG Jinling 2009, 26(4): 609-616.  Abstract ( )   PDF (493KB) ( )   Molecular dynamics simulation is made to study configuration and total energy of 0.5 mol%,2.1mol%,3.8mol% VB transition metal ions (V5+,Nb5+,Ta5+)/TiO2 in rutile at 300K and 101 325 Pa.As 2.1mol% Ti4+ is substituted by dopants,configuration remains well with less mean-square displacements (MSDs),distinct planes of atoms and higher stability.Nb5+ incorporates into TiO6 octahedra well and shows a large solubility in TiO2 compared with V5+ or Ta5+ due to comparable valence and ionic radius between Nb5+ and Ti4+.

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Numerical Solution of Two-dimensional Gross-Pitaevskii Equation for Bose-Einstein Condensation in a Non-harmonic Trap SUN Changyong, ZHOU Yuxin, XIA Qingfeng, ZHAO Jiangang 2009, 26(4): 617-623.  Abstract ( )   PDF (286KB) ( )   A two-dimensional Gross-Pitaevskii equation describing Bose-Einstein condensation in an axial symmetry nonharmonic trap is solved.Converged wave functions,chemical potentials,and internal energies in Bose-Einstein condensation are obtained.Ground-state of Bese-Einstein condensation with atomic interaction is investigated.A comparison between harmonic and non-harmonic traps is reported.

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Electronic Transport of an Organic Molecule LIU Ruijin, WANG Chuankui 2009, 26(4): 624-628.  Abstract ( )   PDF (308KB) ( )   With first principle and hybrid density functional theory,electronic structrue of an organic molecule bis-(4-mercaptophenyl)-ether is calculated.Electronic transport is studied by elastic scattering Green function method.It shows that electronic field has obvious influence on electronic structrue of molecular system.The current and conductance exhibit nonlinear changes.They are close to experimental results.

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Hole Solitons in an Atomic Chain with Double-well Potentials Under Damping XU Haiqing, ZHONG Hongwei, HU Ke 2009, 26(4): 629-632.  Abstract ( )   PDF (169KB) ( )   With a method of multiple scales,a one-dimensional atomic chain with symmetric double-well potentials with damping is investigated.A damped nonliner Schrödinger equation is derived.Analytical solutions of damped hole solitons propagating in the chain are presented.