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25 May 2004, Volume 21 Issue 3 Previous Issue    Next Issue

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A New Subgrid Eddy Viscosity Model and Its Application CUI Gui-xiang, ZHOU Hai-bing, XU Chun-xiao, ZHANG Zhao-shun, L. Shao 2004, 21(3): 289-293.  Abstract ( )   PDF (266KB) ( )   A new subgrid eddy viscosity model is proposed. The new subgird eddy viscosity is proportional to the skewness of longitudinal velocity increment, which characterizes the transportation of turbulent momentum bteween resolved and unresolved turbulence. The new model is verified by a DNS data bank of isotropic turbulence, and has been applied to the turbulent channel flow. The results show to be in good agreement with DNS ones.

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Numerical Simulation of Inertial Confinement Fusion Laser Ablative Interfaces Instability GE Quan-wen 2004, 21(3): 294-304.  Abstract ( )   PDF (563KB) ( )   It studies numerical simulation of two-dimensional hydrodynamic instability and the laser ablative interfaces instability of the inertial confinement fusion by applying the level-set-methods and the ENO method. Numerical examples are given, which demonstrate the efficiency of the present scheme for the numerical siumlation of interfaces instability.

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Three Dimensional Object Oriented Parallel Particle Simulation Code-PLASIM3D MA Yan-yun, CHANG Wen-wei, YIN Yan, ZHUO Hong-bing, XU Han 2004, 21(3): 305-311.  Abstract ( )   PDF (458KB) ( )   A three dimensional object oriented parallel particle simulation code PLASIM3D (using the first three letters of the words "plasma" and "simulator") is developed with the purpose of studying the interaction of laser and plasma. The arithmetic of the code is introduced and its performance is tested and analyzed. The linear speedup is acquired in the present test.

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A Robust Front-tracking Method Based on Conservation for Euler System in One Space Dimension LIU Yan, MAO De-kang 2004, 21(3): 312-318.  Abstract ( )   PDF (365KB) ( )   A conservative front-tracking method[8,9] has been developed. The main feature of the method is that it uses the conservation property of the solution rather than the Hugoniot conditions to track discontinuities. The goal of this paper is to realize the method for the Euler system in an almost second order fashion. Euler system has three different kinds of characteristics, and waves propagate along the characteristics. Thus, to do the front-tracking, in the vicinity of the tracked discontinuities, it is necessary to spearate the waves in other characteristic fields from the tracked discontinuities and then distribute them to the solution on the two sides. An almost second order accurate wave separation procedure be designed, which can separate waves and then distribute them. Numerical examples show the effciency of the method.

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The Design of the Entropy Dissipator of the Entropy Dissipating Scheme for Scalar Conservation Law LI Hong-xia, MAO De-kang 2004, 21(3): 319-326.  Abstract ( )   PDF (376KB) ( )   In our foregoing paper[8] we had designed a nonlinear conservative difference scheme of second-order Godunov type with piecewise-linear reconstruction,in which the slope of the reconstructed function in each grid cell can be computed by dissipating the entropy. Such a scheme satisfies the entropy condition,and computes not only numerical solution but also numerical entropy; thus, it is different from all former conservative schemes. A socalled entropy dissipator in the scheme, which dissipates the entropy in each grid cell in the computation, plays an important role in stabilizing the computation. The entropy dissipator designed in is quite complicated. In this paper, we numerically discuss why entropy must be dissipated and how much entropy should be dissipated. A new entropy dissipator, based on the second-order difference of the numerical solution is given. Numerical examples are presented to show how the entropy dissipator suppresses nonphysical oscillations near discontinuities.

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Numerical Simulation of One-dimensional Atom Lithography HE Ming, LI Ruo-hong, WANG Xiao-rui, WANG Jin, ZHAN Ming-sheng 2004, 21(3): 327-332.  Abstract ( )   PDF (326KB) ( )   Building on direct numerical calculation, it analyzes the dynamics of atoms propagating through a laser standing wave (SW) potential in the regime of immersion-lens.The spot size of Cr atomic deposition is estimated. It is also shown that some physical quantities, such as atomic velocity distribution, laser detuning and laser beam radius, play important roles in determining the quality of atom lithography.

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Common Formulae for Free-order Explicit Multistep Method of Precise Time Integration and the Higher Order Numerical Simulation YAN Hai-qing, TANG Chen, ZHANG Hao, LIU Ming, ZHANG Gui-min 2004, 21(3): 333-338.  Abstract ( )   PDF (280KB) ( )   Common formulae for the free-order explicit multistep method of precise time integration are proposed. When the higher order explicit algorithms of precise time integration are applied for calculating the ray equation and the classical trajectories of diatomic system, the effect is admirable. The numerical results reveal that the pressent method is higher accurated and efficient, capable of keeping computational stability for long time simulation, and suitable for higher order numerical computation.

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Micromagnetism and Monte Carlo Simulation of Magnetism of a Two-Dimension Diluted System WENG Zhen-zhen, FENG Qian, XIAO Yan, LI Yong-sen, HUANG Zhi-gao 2004, 21(3): 339-345.  Abstract ( )   PDF (350KB) ( )   Magnetic feature of a two-dimension ferromagnetic/antiferromagnetic random diluted magnetic system is studied by micromagnetism and Monte Carlo method. The step effect of M-H magnetization curve is found in this system, and discussed with the one-dimension Ising model, which covers the energy of system and the spin configuration. It's found that the step effect can be produced in the antiferromagnetic coupling system with small number of spins.

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PDF Simulation of Fluctuating Behavior of Radiative Source Term in Hydrogent Turbulent Jet Diffusion Flame XU Xiao, LIU Lin-hua, CHEN Yi-liang, WANG Hai-feng 2004, 21(3): 346-350.  Abstract ( )   PDF (353KB) ( )   The laminar flamelet model in combination with joint probability density function (PDF) transport equation of mixture fraction and turbulence frequency is used to simulate fluctuating behavior of radiative source term in turbulent jet diffusion flames of hydrogen.The frequency distributions of radiative source terms in the combustion zone are calculated. The results show that, for the given ensemble, about 95% samples of radiative source term locate within the region of ±3.0 standard deviation of the mean radiative source term. The profile of frequency distribution indicates having a single peak.

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PDF Simulation of Axisymmetric Bluff Body Stabilized Turbulent Diffusion Flame ZHU Min-ming, CHEN Yi-liang, WANG Hai-feng, DONG Gang 2004, 21(3): 351-356.  Abstract ( )   PDF (360KB) ( )   A consistent hybrid FV/MC algorithm developed on triangular unstructured meshes is implemented to simulate turbulent diffusion flame stabilized on bluff body. Monte Carlo method is used to solve joint fluctuating velocity-frequency-composition PDF equation, while Reynolds averaged mass, momentum and energy equations are solved by finite volume method. The coupling between the two methods reduces the statistical and bias error of stand-alone particle method, so accuracy and efficiency are improved greatly. Laminar flamelet model is incorporated. The simulation results are compared with the experimental data.

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Numerical Investigation of Turbulent Mixing in a High Temperature Air Combustion Furnace WANG Li-jun, CAI Jiu-ju, ZOU Zong-shu, KUANG Shi-bo, HAO Yu-ling 2004, 21(3): 357-361.  Abstract ( )   PDF (261KB) ( )   The three-dimensional numerical simulation of the non-premixed combustion turbulent mixing processing in high temperature combustion furnace have been performed with authors developed computer program of flow,combustion,heat transfer and NOx turbulent formation.The 3d-distributions of mixture fraction and its turbulent fluctuation are forecasteed under three different inlet air temperature conditions in combustion furnace.Compared with non-premixed combustion,the results demonstrate that,under certain geometry and dynamical conditions,the turbulent mixing of high temperature air combustion proceeds with smaller intensity within a larger zone; the turbulent mixture fluctuation distributes within the larger combustion zone.This also indicates that the flame thickness appears to be larger and that heat is released within larger combustion zone.The simulating conclusions are in agreement with the results of similar experiments.

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The Principle of Local Tomography with a New Filter XU Mao-lin, QIU Jun, FAN Hui-rong, ZHANG Zhao-tian, LI Xing-dong 2004, 21(3): 362-368.  Abstract ( )   PDF (473KB) ( )   It introduces the principle of local tomography algorithm with a new filter.The second order error estimation is obtained.The local reconstruction of simulation and experimental projection data show that the local tomography algorithm is simple and fast,by which the resolution and Gibbs effect of the reconstructed images can be improved.

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Electronic Properties of Single Carbon Nanotubes with Pentagon-heptagon Pairs Defects HU Hui-fang, ZHANG Li-fang, WANG Xiao-zhi, LIANG Jun-wu 2004, 21(3): 369-372.  Abstract ( )   PDF (237KB) ( )   Using the extended Su-Schriffer-Heeger model,in the real space it investigates the features of energetics, the electronic properties of carbon nanotubes,containing pentagon-heptagon pairs(5/7),pentagon-hexagonal-heptagon (5/6/7) and pentagon-hexagonal-hexagonal-heptagon(5/6/6/7) topological defects in the perfect hexagonal network of the zigzag configuration.The present calculations show that the pentagon-heptagon pair defects on the nanotube structure are not only responsible for a change in nanotube diameter,but also govern the electronic behavior around Fermi level.By calculating the densities of states of the (9,0)-(8,0),(9,0)-(7,0) and (9,0)-(6,0) system,and the densities and band of these heterojuctions have been compared.These results show that the different arranges of pentagon and heptagon along the axi have obvious difference on electrical properties of carbon Nanotube.So different electronic devices based on these heterojuctions can be created.

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Electronic Structure of Ca3Co2O6 and Ni-doped Ones MIN Xin-min, ZHU Lei, XING Xue-lingnd 2004, 21(3): 373-376.  Abstract ( )   PDF (232KB) ( )   The electronic structures of Ca3Co2O6 and Ni-doped ones are calculated using density functional and discrete variation method (DFT-DVM).The relation between electronic structure,chemical bond and thermoelectric property is discussed.The results indicate that the highest valence band (HVB) and the lowest conduction band (LCB)are mainly contributed from Co3d,Ni3d and O2p atomic orbitals.The property of semiconductor is shown from the gap between HVB and LCB.The gap of Ni-doped ones is less than that of Ca3Co2O6.The covalent and ionic bonds of Ni-doped ones are both weaker than those of Ca3Co2O6.The thermoelectric property may be improved from adding Ni element into the system of Ca3Co2O6.

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Analysis of Elastic Cosserat Medium Using Discrete Cosserat Finite Elements ZHENG Chang-liang, REN Ming-fa, ZHANG Zhi-feng, SONG He-ping 2004, 21(3): 377-382.  Abstract ( )   PDF (274KB) ( )   This paper deals with the finite element method of plane couple stress theory. A discrete Cosserat finite element method is proposed. The displacement and rotation fields are interpolated independently. Kinematic constraints between rotation and displacement gradient are imposed in discrete fashions. A 3-nonded, 9-dof (degree of freedom) triangular discrete Cosserat element (called DCT9) is formulated based on discrete Cosserat technique. Numerical results show that DCT9 element can describe mechanical properties of the Cosserate medium.