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25 November 2004, Volume 21 Issue 6 Previous Issue    Next Issue

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PDF Modeling of Local Extinction and Re-ignition Within Turbulent Non-Premixed Flame WANG Hai-feng, CHEN Yi-liang 2004, 21(6): 471-476.  Abstract ( )   PDF (355KB) ( )   A piloted CH4/O2/N2 turbulent jet non-premixed flame (Sandia flame D) is numerically investigated.The summary of the adopted models contains a two-scale k-ε turbulence model,the scalar joint probability density function (PDF) transport equation approach,the augmented reduced mechanism (ARM) for methane oxidation (consisting of 16 species and 12 lumped reaction steps),the Euclidean minimum spanning tree (EMST) small scale mixing model etc.The agreements between the numerical results and the experimental data are good,including the scatter plots and conditional PDFs of scalars as well as the scalar averages.The numerical results indicate that the present models are not only able to represent the macro flame structure accurately,but also can successfully predict the complicated local extinction and re-ignition processes in the turbulent combustion.

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The Coupling of Natural Boundary Element and Finite Element for Semilinear Boundary Value Problems WU Zheng-peng, YU De-hao 2004, 21(6): 477-483.  Abstract ( )   PDF (259KB) ( )   The finite element method is combined with the natural boundary element method to study the weak solvability and Galerkin approximations of a class of semilinear exterior boundary value problems.Theoretical analysis is mainly based on the variational formulation with constraints.The error estimate of the finite element solution and the asymptotic rate of convergence O(hn) are obtained.Finally,a numerical example is devoted to illustrate this new method.

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A New High Order Methods for the Heated Cavity Problem GUO Xiao-hu, TIAN Zhen-fu, ZHANG Lin-bo 2004, 21(6): 484-494.  Abstract ( )   PDF (444KB) ( )   Based on the high accuracy compact difference scheme and the alternating group explicit (AGE) iterative method which has obvious property of parallelism,an AGE iterative method with the fourth-order compact scheme is established for the steady convection-diffusion equation.Numerical solutions are obtained for the model problem of natural convection in a square cavity with large Rayleigh number of physical interest and small Prandtl numbers attempted.Some results of the present are compared with the referenced paper.

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Dynamic Properties of Nonlinear Schrödinger Equation LIU Xue-shen, HUA Wei, DING Pei-zhu 2004, 21(6): 495-500.  Abstract ( )   PDF (335KB) ( )   The dynamic properties of nonlinear Schrödinger equations are investigated numerically by using the symplectic scheme (Euler centered scheme). The dynamic behavior of cubic nonlinear Schrödinger equations with various nonlinear parameter is studied in different phase space.And the dynamic properties of cubic-quintic nonlinear Schrödinger equations are dealt with numerically by using the symplectic scheme. The dynamic behaviors of cubic-quintic nonlinear Schrödinger equations with different cubic and quintic nonlinear parameters are discussed in the phase space.It shows that the route varies with different cubic nonlinear parameters and with the increase of the quintic nonlinear parameters.

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Lattice Gas Simulation of Thermoacoustic Prime Movers LIU Xu, CHEN Yu, ZHANG Xiao-qing 2004, 21(6): 501-504.  Abstract ( )   PDF (321KB) ( )   A 9-bits lattice gas model with temperature effect is applied into the simulation of thermoacoustic prime movers. The self-excited oscillation in a thermoacoustic resonant tube has been simulated. The distribution of two-dimensional temperature field and the evolution process of temperature are presented as well. The effects of the length of stack and of its position on acoustic pressure have also been investigated numerically. The simulation results are valuable to the optimum design of stack. The validity of the lattice gas model for a thermoacoustic engine has been verified by the comparison of the simulated and experimental results, which demonstrates that the lattice gas method is suitable for the thermoacoustic simulation.

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Numerical Calculation of Soliton Transport in Trans-polyacetylene Under an External Electric Field ZHU Rui, TIAN Qiang 2004, 21(6): 505-508.  Abstract ( )   PDF (213KB) ( )   Soliton dynamics is simulated for trans-polyacetylene single-chain systems using the Su-Schrieffer-Heeger (SSH) model with an additional part to include an external electric field. It is shown that the soliton moves along the chain with a constant speed when an external electric field is applied.

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Boundary Condition for Obliquely Incident Laser in Particle Simulation LI Bin, LIU Zhan-jun, ZHENG Chun-yang, ZHU Shao-ping 2004, 21(6): 509-514.  Abstract ( )   PDF (356KB) ( )   Lindman boundary condition is adopted in particle simulation code LARED-P. Using this code, obliquely incident laser propagation in plasma is numerically studied, with enough testing computation, it is convinced that Lindman BC can officiently diminish wave reflection into simulation area.

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A Stochastic Model of Heavy Particle Dispersion in Turbulent Boundary Layer GUO Yu, CUI Gui-xiang, XU Chun-xiao, ZHANG Zhao-shun, Michel AYRAULT 2004, 21(6): 515-522.  Abstract ( )   PDF (395KB) ( )   A stochastic model of heavy particle dispersion is proposed.It is based on the coupling of the stochastic equation of turbulent fluid motion with the heavy particle crossing trajectory equation in which Saffman force,particle-wall collision and particle-particle collision are included.The model is also tested in a turbulent boundary layer with heavy particles.The numerical results are in good agreement with previous experimental data.The effect of Saffman force and particle collision on the heavy particle dispersion is investigated numerically as well.

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An Adaptive Wavelet Precise Integration Method for Partial Differential Equations MEI Shu-li, LU Qi-shao, ZHANG Sen-wen 2004, 21(6): 523-530.  Abstract ( )   PDF (437KB) ( )   Taking the Burgers equation as example, an adaptive multilevel interpolation quasi-wavelet collocation method for the solution of partial differential equations is developed. In this method, an adaptive multilevel quasi-wavelet collocation interpolation operator is constructed according to the interpolation wavelet theory, and then the equations can be discreted adaptively in physical space. On the other hand, the extrapolation and precise integration method is helpful for decreasing computation time and improving calculating precision, and it make the selection of time step for integration self-adaptive.

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Numerical Computations of the Refraction of a Shock Wave at Interface by Multi-component PPM Algorithm WANG Chen-xing, TANG Wei-jun, CHENG Jun-bo 2004, 21(6): 531-537.  Abstract ( )   PDF (375KB) ( )   It presents numerical computation results of the refraction of a plane shock wave at the different interfaces. The unsteady, two-dimensional, compressible, Euler equations are solved numerically assuming stiffened gas equation of state. The numerical method used is PPM (Piecewise Parabolic Method) method for multi-component. On basis of solving the Riemann problem using two-shock approximation the interface can be determined by computing the volume-fraction in terms of the high-order PPM method in the whole computational field. This method is also used to compute some case of the inter-action when the shock wave meets the interfaces of the different fluids. It also gives the evolvement of interfaces due to baroclinic effects on the interface, especially in the cases of strong shock striking at the interfaces.

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Particles Reynolds Stresses Trajectory Model and Numerical Simulation for a Backward-facing Step Two-phase Flow XU Jiang-rong, ZHOU Zhi-jun, ZHANG Wei, ZHOU Jun-hu, CEN Ke-fa 2004, 21(6): 538-542.  Abstract ( )   PDF (272KB) ( )   A Lagrangian equation of v'giv'pi on the particles trajectory is obtained with stochastic process theory, and then Lagrangian equation of particle Reynolds stresses is exactly set up. Wang Stock experiment on heavy particle dispersion considered scale ratio and flow decay is simulated by both this method and Zhang's model[1]. Simulation results show the new method is better than Zhang's model. A backward-facing step two-phase flow is calculated by the new model and the results show good agreement with the experiment results.

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Electronic Structure and Poling Characteristics of Na1/2Bi1/2TiO3 System CHEN Wen, ZHOU Jing, XU Qing, LI Yue-ming, Sun Hua-jun, MIN Xin-min 2004, 21(6): 543-546.  Abstract ( )   PDF (270KB) ( )   The electron structure of the Na1/2Bi1/2TiO3 system with ABO3 type perovskite structure is studied by using self-consult charge-discrete variation-Xα (SCC-DV-Xα) method, and the effect of A, B position substitute on poling characteristic is also analyzed. The calculational results show that spontaneous polarization exists in the NBT piezoceramics system, the piezoelectric properties are enhanced because of the displacement of the B position ions, in addition, the compound substituent of Ba, Sr and Mn ion can decrease coercive field, and increase the strength of spontaneous polarization, so the dielectric properties get improved.

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Finite Element Solution of Radiative Heat Transfer in a Rectangular Enclosure with Participating Media QI Hong, RUAN Li-ming, TAN Jian-yu 2004, 21(6): 547-550.  Abstract ( )   PDF (340KB) ( )   The finite element method is applied to solve the radiative heat transfer equation and energy conservation equation discretely.This paper provides an exact solution of the mean incident intensity and the temperature distribution in a rectangular geometry in a absorbing,emitting,isotropically scattering media enclosed by black and gray diffuse surfaces.The validity of this method is examined by comparing the present results with the those available of Monte Carlo simulation (M-C).Numerical results show that the present method can satisfactorily predict the radiation transfer.

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The Geometrical Configuration and Potential Curve of PuH3 ZHU Sheng-xiang, XUE Chun-rong, XIAO Zhi-gang 2004, 21(6): 551-557.  Abstract ( )   PDF (448KB) ( )   Until now,there are very little public data about the molecular structures and molecular spectroscopy in plutonium hydride.The different geometrical structures and potential energy curves of the molecule PuH3 are calculated with the discrete variational method (DVM),which is based upon the density functional theory.The optimal data of pyramidal molecule PuH3 on the ground level are as follows:bond angle θ (H-Pu-H)=119.102°,bond length Pu-H=2.097726Å,the distance of H-H is 3.616817Å,total orbital energy is -19868.834 a.u.,Fermi energy level Ef=-16.856eV.The equivalent molecular state in inverse symmetry and the total orbital energy in mass centric coordinates are discussed.With full-electronic calculation,the results of PuH2 and PuH3 are compared.

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The Analytical Solutions of Mathematical Model for a Fractal Composite Reservoir with Non-Newtonian Power Law Fluids Flow XIANG Kai-li, TU Xiao-qing 2004, 21(6): 558-564.  Abstract ( )   PDF (283KB) ( )   The Theories and model of well testing analysis for a fractal composite reservoir have been discussed with non-Newtonian power law fluid flow. In order to completely describe the situation of real reservoirs, the fractal composite reservoir is defined as fractal reservoir that consists of many zones with different fluid and different format properties. The initial and three outer boundary conditions such as infinite, finite with constant pressure and closed boundary have been given according to polymer flooding in an oil field. A new effective well radius mathematical model of this fractal composite reservoir is suggested involving the wellborn storage and skin effects. The analytical solutions in Laplace-space for the mathematical model and two special cases of two and three regions are derived by Laplace transformation. The dimensionless wellborn pressure for the modern well test analysis is given by using Stehfest numerical inversion. The well test analysis theories and the pressure behavior of this reservoir are also discussed for the two region model.