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25 January 2009, Volume 26 Issue 1 Previous Issue    Next Issue

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Algebraic Two-level Iterative Method for 2-D 3-T Radiation Diffusion Equations XU Xiaowen, MO Zeyao, AN Hengbin 2009, 26(1): 1-8.  Abstract ( )   PDF (465KB) ( )   A two-level iterative method is proposed for linear systems discretizated from two-dimensional(2-D) radiative diffusion equations with photon, electron,ion temperatures(3-T).The main idea is to decouple one temperature from other two by a special coarsening strategy.Variables related to electron temperature are forced to be selected as coarse points and photon and ion temperatures are forced to be fine points.Several single temperature equations instead of coupled linear systems need to be solved by a classical-AMG method.The method is applied to the JFNK framework for preconditioning.Numerical results show effectiveness of the method.

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SIMPLEC Algorithm with Unstructured Grids Considering Coupling of Density and Temperature LEI Guodong, LIU Gongmin, ZHANG Wenping, ZHU Minggang 2009, 26(1): 9-16.  Abstract ( )   PDF (465KB) ( )   An algorithm with unstructured girds is introduced in which coupling of density and temperature is considered.Static enthalpy equation is employed to construct relation between temperature correction and pressure correction.As in Rhie-Chow method,temperature and pressure corrections of grid interfaces are interpolated by static enthalpy equation and omitting neighbour temperature correction as in the velocity-pressure coupling in SIMPLEC.CGNS is taken as I/O in the in-house unstructured FVM code.For combustion simulation,Arrinius-Eddy dissipation model is employed.

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Discretization of Two-dimensional Advection-Diffusion Equation with Unstructured Cell Center Finite Volume Method GENG Yanfen, WANG Zhili, LU Yongjun 2009, 26(1): 17-26.  Abstract ( )   PDF (459KB) ( )   In a two-dimensional shallow water flow model advective-diffusion derivative equation is discretized with cell center finite volume method.Flux reconstruction and support operators method are used for advective and diffusive terms,respectively.The model is second order and can be used for arbitrarily unstructured grids.A pure advective problem and a pure diffusion problem verify the algorithm.The model is used to simulate salt transport in Oujiang estuary.Water level,velocity and salt calculated are in good agreement with measurement.

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Chemistry Acceleration Algorithm for Gaseous Detonation DONG Gang, FAN Baochun 2009, 26(1): 27-34.  Abstract ( )   PDF (468KB) ( )   A dynamical storage/deletion algorithm for acceleration of chemical reaction calculation is proposed which deals with stiff chemical source term in reactive flows.The algorithm is applied to two-dimensional gaseous detonation.Two deletion approaches, global deletion and node deletion,are developed and compared with traditional direct integration(DI) algorithm.It shows that the proposed algorithm ensures computational accuracy and relaxes stringent limitation on computer memory.With fixed size of data table,computational speedup factor increases with increament of tolerance error.With same tolerance error,speedup factor of node deletion approach is higher than that of global deletion.The algorithm shows advantages in solving transient reactive flows.

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Reordering Method for Two-dimension Three-temperature Energy Equations ZHANG Yong, HUANG Tingzhu, LIU Xingping, GU Tongxing, LI Houbiao 2009, 26(1): 35-41.  Abstract ( )   PDF (291KB) ( )   A reordering method,named alternate hyperplane ordering,is proposed to solve linear systems from two-dimension three-temperature nonlinear energy equations.Numerical experiments are performed with Krylov subspace iterative associated ILU(k) preconditioning.It is showed that with nearly same preconditioning cost,the proposed ordering method is better than red-black ordering and hyperplane ordering etc.

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Monte Carlo Simulation of Liquid Self-diffusion with Surface Relaxation CAI Shuhui, CHEN Qiaolong, CAI Congbo 2009, 26(1): 42-48.  Abstract ( )   PDF (349KB) ( )   Time-dependent self-diffusion coefficients and magnetization attenuation of liquid with surface relaxation in porous media in an infinitely long cylinder are calculated with Monte Carlo random walk method.Relationship between parameters of NMR relaxation and random walk is obtained.In fast-diffusion area, magnetization of nuclear spins attenuates exponentially,and self-diffusion coefficients are independent of surface relaxivity within short diffusion time.In slow-diffusion area,both magnetization attenuation and self-diffusion coefficients are independent of surface relaxivity within short diffusion time.These results agree well with theoretical analysis.Surfaceto-volume ratio and pore size can be determined.

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Simulation of Multiphase Flows in Microscale Hemodialysis XU Kan, LIU Minghou, LIU Dong, CHEN Yiliang 2009, 26(1): 49-56.  Abstract ( )   PDF (426KB) ( )   A non-Newtonian shear-thinning model is shown and applied to multiphase flow simulation in 3-D micro-tubes.The model is validated by comparing simulation and experimental results.Velocity simulated agrees well with experimental data and shows F-L effect in microscale hemodynamics.To investigate non-membrane hemodialysis,we simulate hemodialysis in a T-shape mixer.Simulation indicates that components with larger mass diffusion coefficient pervade sufficiently and they can be separated from other components.

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Boundary Layer Flows with One Atmosphere Uniform Glow Discharge Plasma MAO Meiliang, DENG Xiaogang, CHEN Liangzhong, CHEN Jianqiang 2009, 26(1): 57-63.  Abstract ( )   PDF (364KB) ( )   In a model for interaction between one atmosphere uniform glow discharge plasma (OAUGDP)and air proposed by Shyy,electric field and electric forces acting on air as body force are obtained.The electric field is calculated with electric potential equation. The influence of OAUGDP on flows around a NACA0015 airfoil at low speed is investigated by solving N-S equation with a body force term.Plasma located upstream of the separation point damps the flow separation around the airfoil efficiently,while plasma located downstream of the separation point has little effect on the flow.It agrees with experimental observations. Effect of plasma on aerodynamics of airfoil and pressure distribution on airfoil surface are investigated.

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GSS-3 Molecular Model in Monte Carlo Simulation WANG Xuede, WU Yizhao, XIA Jian, LIN Xiaohong 2009, 26(1): 64-70.  Abstract ( )   PDF (300KB) ( )   With Lennard-Jones interaction potentials a GSS-3 molecular model is proposed to study transport properties of gas,such as coefficient of viscosity,self-diffusion and diffusion of molecules.The model is applied to unstructured direct simulation Monte Carlo method.Numerical results confirm feasibility of the model.

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Monte Carlo Simulation of Electron Transport in a Nitrogen Plasma Gun SUN Fengjiu, YU Hanjiang, ZHANG Jun 2009, 26(1): 71-77.  Abstract ( )   PDF (333KB) ( )   Monte Carlo simulation on electron transport in nitrogen glow discharge between drilled electrodes in a plasma ion source is presented.Collision probabilities of electron-molecule,average energy and exit angle of outgoing electrons are calculated.Energy distribution of electron calculated follows approximately Boltzmann distribution.With increasment of E/N,electron average energy and probabilities of electric excitation,dissociation,ionization,dissociative ionization collisions are increased.Nonuniform electric field between electrodes enhances ionization rate and electron average energy obviously.

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Spurious Magnetic Field Divergence Cleaning in Magnetohydrodynamic Simulation TIAN Zhengyu, ZHANG Kangping, DING Guohao, LI Hua 2009, 26(1): 78-86.  Abstract ( )   PDF (643KB) ( )   Numerical technique is developed to clean spurious magnetic field divergence ▽·B in full MHD (Magnetohydrodynamics) simulation.Eight-wave equations are solved in basic scheme combined with additional source term ▽·B to keep conservation.A projection scheme is used to clean spurious magnetic field divergence.3D Poisson equation is solved with a finite volume method.For smooth analytical field,▽·B is cleaned efficiently.While for hypersonic MHD blunt flows with shock wave,▽·B error increases sharply in free stream region.A local projection scheme is proposed to clean ▽·B in relatively high divergence region. Flow field converges well and magnetic field divergence in low divergence region is not influenced.

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Wavelet-Homotopy Hybrid Algorithm for Inverse Problem of Ground Penetrating Radar LI Zhuang, HAN Bo, CHEN Yong 2009, 26(1): 87-93.  Abstract ( )   PDF (427KB) ( )   A wavelet-homotopy hybrid inversion algorithm for inverse problem of ground penetrating radar (GPR) is proposed.Wavelet is applied to separate inverse problem into different scales.In the maximum scale,initial value of the next scale is found by a homotopy method.In other scales,iteration process is carried out to obtain the global minimum point.The algorithm takes advantages of wavelet analysis and homotopy inversion method.It shows high capability of global search.

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Lattice Boltzmann Heat-transfer Models with Different Accuracy DONG Zhiqiang, LI Weizhong 2009, 26(1): 94-100.  Abstract ( )   PDF (362KB) ( )   Lattice Boltzmann thermal models with second-order accuracy are obtained with an extra parameter term.They are employed to Rayleigh-Benard convection heat transfer and are compared with original models.In order to reduce error of Nu number at large Ra number and thermal diffusivity,we analyze truncation error of corresponding heat-transfer equation and introduce an adjusting parameter in the equilibrium distribution function.Applicability of LBM heat-transfer models is extended.

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P3 Approximation in Spherical Harmonics Method for Radiative Transfer Equation and Application in Biological Tissues CHAI Chenggang 2009, 26(1): 101-106.  Abstract ( )   PDF (251KB) ( )   P3 approximation of raditive transfer equation in spherical coordinate results nonlinear differential equations.Their solution are spherical Bessel functions. Particular solutions are obtained with variation of parameters in exponenital representation of spherical Bessel functions.Approximation boundary condition of Marshak and others can not be satisfied due to solution discontinuity at r=0.It is solved by energy conservation with approximation of P3 by P1 as absorption coefficient is much lower than reduced scattering coefficient.Compared with Monte Carlo and analytic solutions of P3 approximation,it is found that P3 approximation deals with biological tissues with ratios of reduced scattering coefficient to absorption coefficient from 2 to 10.

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Unified Time Scale Algorithm for Thermal Effect of MESFET Under Irradiation of High Power Electromagnetic Pulses TIAN Guangkun, HUANG Kama 2009, 26(1): 107-113.  Abstract ( )   PDF (295KB) ( )   We propose a unified time scale algorithm for thermal effect of MESFET under irradiation of high power electromagnetic pulses.Electromagnetic equations,heat transfer equations and carrier equations are solved effectively.Numerical stability and calculation errors are discussed.A practical MESFET is calculated.Simulated results agree well with measured results.

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Flexoelectric Effect on Electro-Optical Characteristics of a Nematic Liquid Crystal Cell YE Wenjiang, XING Hongyu, ZHANG Zhidong, CHEN Guoying 2009, 26(1): 114-120.  Abstract ( )   PDF (274KB) ( )   Flexoelectric effect on electro-optical characteristics of a nematic liquid crystal cell is investigated.Differential equations and boundary conditions for director of liquid crystal are obtained with variation theory.Distributions of director of nematic liquid crystal (NLC) cells with strong anchoring and weak anchoring are calculated by a finite-difference iterative method.With Jones matrix method,transmittance-voltage characteristics of liquid crystal cells are obtained.Surface flexoelectric effect and bulk flexoelectric effect are considered.

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Molecular Dynamics Study on Structural Stability of Ag Nanorods with Crystallographic Orientation [111] LU Min, LIU Weiqing, LUO Fei, WEI Wanghe 2009, 26(1): 121-128.  Abstract ( )   PDF (463KB) ( )   A three-dimensional molecular dynamics method with Finnis-Sinclair embedded atom potentials is used to study relaxtion of fcc Ag nanorods with crystallographic orientation[111] .Homeostasis of Ag nanorod relaxation is shown.Stable structures and potential energies and structure evolution of Ag nanorod are studied. A critical temperature of destabilization(Tc) is found.As temperature of the nanorod is less than Tc,the system keeps intact line form of crystal.As temperature is higher than Tc and less than melting point,the system collapses,fuses and then recrystallizes.As temperature is near melting point,a stable polyhedron bounded by(111) and(100) facets forms. As cross-section of Ag nanorod increases Tc and melting point decrease.As cross-section dimension is larger than 2 nm,Tc is close to the melting point.Destabilization exists in a narrow temperature range.

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Nonlinear Buckling Analysis of Tubular in a Deviated Well with Differential Quadrature Element Incremental Iteration Method GAN Lifei, WANG Xinwei, TAN Meilan 2009, 26(1): 129-134.  Abstract ( )   PDF (297KB) ( )   Equilibrium equations of tubular in a deviated well are presented.A differential quadrature element(DQE)incremental iteration method is established to analyze nonlinear buckling of tubular in a deviated well.The method is verified with result of finite element method.It exhibits advantages of easy implementation,low computational cost and higher accuracy.Helical buckling by DQE agrees well with experimental data.The maximum constraint force increases with increasing of upper end load.It is found that the buckling of long tubular is a local buckling problem.The buckling starts from the lower end and propagates upward with increasing applied load.Boundary conditions at upper end have little influence on local buckling of lower tubular.

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Finite-difference Method for Thin Plate Bending XIE Wenhao, QU Xiaogang 2009, 26(1): 135-140.  Abstract ( )   PDF (221KB) ( )   According to the principle of minimum potential energy, finite difference schemes for small deflection bending of thin elastic plates with edge beams are obtained with FDM based on the principle of variation.The schemes depend only on mesh points in plates .They avoid problems with fictitious mesh points.Difference equations are programed with MATLAB and numerical simulations are shown.

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Quantum Key Generation Rate of Decoy State Quantum Key Distribution with Heralded Single-photon Source QUAN Dongxiao, PEI Changxing, MA Huaixin, LIU Dan, YAN Yi 2009, 26(1): 141-146.  Abstract ( )   PDF (253KB) ( )   Quantum key generation rate of decoy state quantum key distribution(QKD) with a heralded single-photon source(HSPS) is deduced.Relationship between quantum key generation rate and detection efficiency of sender is discussed.Optimal intensities and key generation rate of decoy state QKD with a weak coherent pulse(WCP) and an HSPS are analyzed.It shows that key generation rate increases with increase of detection efficiency of sender and its security distance is the same as with a perfect single photon source.Decoy state QKD increases security distance and key rate of QKD.Due to less dark counts QKD with HSPS works longer distance than WCP.

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Classical Dynamics of One-dimensional Hydrogen Molecule in Two-color Intense Laser Field JIA Lina, GUO Jing, LIU Xueshen 2009, 26(1): 147-151.  Abstract ( )   PDF (227KB) ( )   Dynamics of one-dimensional hydrogen molecule in two-color intense laser field is studied with classical theory and symplectic algorithm.Classical trajectories are obtained by solving Hamiltonian equations numerically. Probabilities of H2+,H22+,H,H+ are evaluated.Classical dynamics caused by laser intensity,frequency,and phase are illustrated and explained.

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Monte Carlo Simulation on Topology of DNA Minicircles LIU Yanhui, HU Lin 2009, 26(1): 152-158.  Abstract ( )   PDF (283KB) ( )   Metropolis-Monte Carlo simulation is made to investigate autocorrelation of conformation energy and tangent vectors of minicircles(less than 500 base pairs) with flexible hinges.Direct conformation information and topology of minicircle containing flexible hinges are demonstrated.It provides powerful support for the existence of flexible hinge.