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25 January 2008, Volume 25 Issue 1 Previous Issue    Next Issue

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Diffusion-synthetic Acceleration Method for Diamond-differenced Discrete-ordinates Radiative Transfer Equations LI Shuanggui, FENG Tinggui 2008, 25(1): 1-6.  Abstract ( )   PDF (323KB) ( )   A consistent linear multifrequency-grey acceleration scheme is developed to accelerate the iterative convergence speed of diamonddifferenced multigroup radiative transfer equations. A difference scheme of acceleration equation is obtained directly by applying discrete P1 approximation to differenced SN equations. Numerical examples show that the method is effective and robust.

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Tangential Flux on Grid Edge in Nine-point Schemes for Diffusion Equations YUAN Guangwei, HANG Xudeng 2008, 25(1): 7-14.  Abstract ( )   PDF (349KB) ( )   A discrete tangential flux on grid edge in nine-point schemes for solving diffusion equations on arbitrary quadrilateral meshes is derived. The discrete tangential flux is represented as a weighted combination of difference of center values with adaptive weighted coefficients, which depend on the thermal conductivity and geometric parameters of distorted meshes.

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Physical Considerations in Deuterium Fusion Explosion Cave Design for Power Generation LIU Chengan 2008, 25(1): 15-21.  Abstract ( )   PDF (379KB) ( )   Physical considerations in explosion cave design of 10 kt TNT nuclear explosion of deuterium fusion are analyzed. The lowest quantity of heat carrier(sodium) is estimated. Physical factors affecting sodium vaporization and damping shock waves are analyzed. The action intensity in the nonstationary process of nuclear explosion——shock waves on the outer wall and durability of outer wall are qualitatively evaluated.

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Formulation of Edge-centered Artificial Viscosity Unstructured Mesh GE Quanwen, LIN Zhong, WANG Ruili 2008, 25(1): 22-28.  Abstract ( )   PDF (419KB) ( )   With artificial viscosity and total variation diminishing advection limiter, the edge-centered artificial viscosity with structure zones is extended to unstructured grids, The limiter is constructed by neighbor edges determined by maximum angle choice. The edge-centered artificial viscosity is compared with the zone-centered artificial viscosity. Numerical results demonstrate accuracy and efficiency of the edgecentered artificial viscosity in capturing shock discontinuous.

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A Fifth-order Semi-discrete Central-upwind Scheme for Hyperbolic Conservation Laws HU Yanmei, CHEN Jianzhong, FENG Jianhu 2008, 25(1): 29-35.  Abstract ( )   PDF (394KB) ( )   A fifth-order semi-discrete central-upwind scheme for hyperbolic conservation laws is proposed. In one dimension, the scheme is based on a fifth-order central weighted essentially non-oscillatory(WENO) reconstruction:In two dimensions, the reconstruction is generalized by a dimension-by-dimension approach. A Runge-Kutta method is employed in time integration. The method requires neither Riemann solvers nor characteristic decomposition and therefore enjoys main advantage of the central schemes. The present scheme is verified by one and two dimensional Euler equations of gas dynamics and shows high resolution and high accuracy.

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2D Simulation of an Ag Planar Target Driven by Focus-line Laser ZHENG Wudi, ZHANG Guoping 2008, 25(1): 36-42.  Abstract ( )   PDF (597KB) ( )   Physical equations and calculation methods of XRL2D code, a 2D non-equilibrium radiation hydrodynamics code, are introduced. With this code, three different ALE methods are adopted to simulate hydrodynamic behavior of focus-line plasma of an Ag planar target driven by pre-main-pulse laser, which is a typical Ni-like Ag-ray laser experiment on ShenguangⅡ. The methods give similar and clear physical pictures:abundance distribution of Ni-like ion shows a shape of bow which agrees with distribution of XRL intensity in experiment. The methods are compared in detail as well.

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Development and Application of Multi-dimensional Particle-in-cell Codes for Investigation of Laser Plasma Interactions CHEN Min, SHENG Zhengming, ZHENG Jun, MA Yanyun, ZHANG Jie 2008, 25(1): 43-50.  Abstract ( )   PDF (637KB) ( )   A multi-dimensional particle-in-cell code KLAP is introduced. Field ionization, impact ionization and two body collision are considered in a one-dimensional code. Moving window technology is used in a three-dimensional code to study laser wakefield acceleration in GeV region. Terahertz radiation, laser propagation in neutral gas medium, surface electron acceleration as well as GeV electron generation in laser wakefield acceleration are studied.

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Implicit Iteration Time-advancement Scheme for Compressible Navier-Stokes Equations GAO Hui, ZHOU Xiaojun 2008, 25(1): 51-57.  Abstract ( )   PDF (449KB) ( )   According to the characteristics of compressible flows with wall boundary conditions, a simplified iterative-implicit timeadvancement scheme combined with high order compact difference schemes based on a non-uniform grid system is proposed to solve compressible Navier-Stokes equations, An iteration convergence criterion is given. The computational efficiency is greatly improved. The new scheme is applied to simulate two-dimensional compressible flat-plat laminar boundary layer flows and two-dimensional compressible channel flows.

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Numerical Investigation of One-dimensional Overdriven Detonation Initiation TENG Honghui, JIANG Zonglin 2008, 25(1): 58-64.  Abstract ( )   PDF (457KB) ( )   One-dimensional overdriven detonation initiation is investigated numerically within a finite rate detailed chemical reaction model. Numerical results exhibit that due to upstream inflow at high temperature, pressure and velocity, a leading shock followed by induction and heat-release zones appears. Because of inflow disturbances, the interface between induction and heat-release zones becomes unstable and overdriven detonation waves are generated. With simulation of unstable interfaces with different gas species, temperatures, inflow pressures and velocities, overdriven detonation initiation process is analyzed and illustrated.

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Massive Parallelization of Gas-kinetic Algorithm for Boltzmann Model Equation LI Zhihui, ZHANG Hanxin 2008, 25(1): 65-74.  Abstract ( )   PDF (855KB) ( )   In a numerical study of Bohzmann model equation, a gas-kinetic finite difference scheme with coupling and iteration is constructed to solve molecular velocity distribution function directly. The parallel strategy is established by using parallel technique of domain decomposition based on variable dependency relation, data communication and parallel expansibility. Gas-kinetic HPF(High Performance Fortran) parallel algorithm is developed to solve three-dimensional problems in various flow regimes. Hypersonic gas flows around a sphere and a spacecraft at various Knudsen numbers, Mach numbers and flying angles are computed at a high performance computer with massive scale HPF parallel. The computational results are in good agreement with experimental and theoretical ones. It is shown that the parallel speed-up increases approximately linearly with the numbers of processors. It indicates high parallel efficiency and expansibility with good load balance and data communication. It suggests that a gas-kinetic parallel algorithm on large scale can be used for three-dimensional complex hypersonic flow problems in various flow regimes.

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Numerical Simulation of Micro Flows Considering Wall Adhesion SONG Yu, WANG Fei, HAO Pengfei, HE Feng 2008, 25(1): 75-82.  Abstract ( )   PDF (405KB) ( )   Level set and volume of fluid(VOF) methods for incompressible two-phase micro flows considering wall adhesion are presented. In the level set method, based on staggered MAC grid, a second-order projection method is carried out to solve 2D Navier-Stokes(N-S) equations and level set function. In the VOF method, the volume fraction of each phase in each computational cell is employed. Variables and properties of flow are computed to represent volume-averaged values. The interface between fluids is traced with solution of a continuity equation for volume fractions. Computational results are shown and compared with experimental results.

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Simulation of Steady Laminar Flow Within a Quarter-circular Cavity by Lattice Boltzmann Method SHI Weiping, ZU Yingqing, YAN Yuying 2008, 25(1): 83-86.  Abstract ( )   PDF (285KB) ( )   A numerical scheme based on lattice Boltzman method(LBM) is presented to deal with curved boundaries with second-order accuracy. The scheme is applied to steady laminar flow within a quarter-circular cavity with curved boundaries and proved to be relatively reliable, accurate and feasible. Streamlines and vorticity contours are obtained to analyse the variation of flow field with Reynolds number. The radian between verticity centre of clockwise flow and x-axis decreases with increase of Re from 10 to 100, while the radian between verticity centre of anticlockwise flow and the x-axis shows inverse tendency.

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Numerical Study of Two-dimensional Hydrodynamic Equations for Dielectric Barrier Discharge with Atmospheric Pressure ZHANG Wenjing, ZHANG Mei 2008, 25(1): 87-91.  Abstract ( )   PDF (502KB) ( )   In a fluid model of DBD(dielectric barrier discharge) with atmospheric pressure, a finite difference algorithm with fixed grids is adopted to solve two-dimensional fluid continuous equations by using four-order and six-order phase error FCT(flux-corrected transport) methods, respectively. With uniform initial conditions, spatial evolution of the electron density during avalanche propagation is studied. Two FCT algorithms are compared in detail. The simulation agrees with theoretical and experimental results. It demonstrates high accuracy and precision of the FCT method.

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Thermal-stability and Tensile Properties of Single-walled Si-H Nanotubes SHEN Haijun, SHI Youjin 2008, 25(1): 92-96.  Abstract ( )   PDF (316KB) ( )   With a Tersoff-potential based MD(molecular dynamics) method, thermal-stability and tensile properties of Sio-H(hydrogenated outside) and Siio-H(hydrogenated outside and inside) single wall nanotubes are investigated. Compared with a(14,14) carbon nanotube, the axial-tensile properties of Sio-H and Siio-H nanotubes are discussed. The results show:1)The Sio-H and Siio-H nanotubes have similar Si skelectons with t {110} crystal-pane of a single-crystal silicon and exist stably only at a temperature lower than 150 K and 75 K, respectively. 2) Sio-H and Siio-H nanotubes have anti-tensile strength of 4.0 and 1.2 GPa, and fracture strain of 35% and 32%, respectively, which are much lower than those of a(14,14) carbon nanotube.

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First Principle Study of Magnetism and Electronic Structure of Fen/Urn Superlattices LI Hengshuai, HU Haiquan, REN Zhongmin, CUI Shouxin 2008, 25(1): 97-100.  Abstract ( )   PDF (254KB) ( )   Electronic structure and magnetism of Fen/Crn superlattices(SL) with various layer thickness(n=1,3,5) are studied using a full-potential linearized augmented plan-wave(FLAPW) method within a density functional formalism. It is shown that ferromagnetic state is a preferable phase in the ground state and the intrinsic spin density wave length is about 2 monolayers(ML). The magnetic moment of Fe layer is slightly modified by an intelvening Cr layer, and becomes stronger with the increase of n. The direction of Cr magnetic moment alternates layer by layer. An antiferromagnetic coupling hetween interfacial Fe and Cr layers is observed. There is a moderate hybridization between d-states of Fe and Cr atoms near Fermi energy.

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Zero Dispersion Point Adjusted by Structural Parameters of TIR-PCF with Six-fold Rotation Symmetry （C6v） TANG Bingshu 2008, 25(1): 101-105.  Abstract ( )   PDF (380KB) ( )   Zero dispersion point adjusted by structural parameters of TIR-PCF with six-fold rotation symmetry is studied numerically with a multipole method. It is indicated that the zero dispersion point is hardly influence.d by the number of air holes in cladding with large relative apertures. The wavelength of the zero dispersion point becomes shorter with larger size of air holes and longer with larger distance between air holes. As size and distance are small, zero dispersion point appears in a long wavelength region. As size and distance are large enough, the dispersion curve oscillates near the zero dispersion point and several zero dispersion points appear. With constant number of air holes in cladding, the adjustment for zero dispersion point by the number of absent air hole in center core is large.

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Decomposition Projective Method with Multi-subspace and Its Convergence SUN Lianyou, HONG Wei 2008, 25(1): 106-112.  Abstract ( )   PDF (414KB) ( )   A decomposition projective method(DPM) is presented to solve large-scale electromagnetic field boundary condition problems. Theoretical analysis shows that its convergence ratio is geometrical and mainly affected by the length of inner boundary of subdomains. Numerical results are coincident with theoretical analysis.

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Evaluation of Nearly Hyper-singular Integrals in Thermal Stress Boundary Element Method CHENG Changzheng, NIU Zhongrong, ZHOU Huanlin, YANG Zhiyong 2008, 25(1): 113-118.  Abstract ( )   PDF (316KB) ( )   An algorithm is developed to calculate stresses at the interior points near boundary in boundary element method of thermoelasticity. A series of transformations is manipulated on conventional derivative boundary integral equations(BIE). It leads to a new natural BIE in thermoelasticity problem named thermal stress natural boundary integral equation(NBIE). Hyper-singularity and strong-singularity in conventional BIE are converted into strong-singularity in NBIE. Nearly strong singular integrals are evaluated in NBIE by the regularization algorithm. Thermal stresses at points near boundary are calculated by NBIE. Numerical examples illustrate efficiency of the method.