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25 September 2000, Volume 17 Issue 5 Previous Issue    Next Issue

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LINEARIZED AUGMENTED PLANE-WAVE CALCULATION OF COHESIVE ENERGY OF BINARY COMPOUNDS ZHANG Jian-zhong, ZHOU Yu-mei, WANG Ding-sheng 2000, 17(5): 467-475.  Abstract ( )   PDF (245KB) ( )   The total energy and cohesive energy of typical binary compounds, namely, NiAl, SiC, GaAs, MgS and NaCl, are studied by using he linearized augmented plane-wave method. Special emphasis is put on the effects of the choice of muffin-tin radii of the two elements. Results show that, for closely packed alloy NiAl, the variation of MT radius yields little change to the total energy; and the atomic covalent radii could be used in setting the MT radii for covalent crystals such as SiC and GaAs; but the ionic radii are not appropriate for crystals with strong ionic bonds such as MgS and NaCl due to a large number of core electrons lost out of the mufin-tin spheres of cations. The calculated cohesive energies with proper choice of muffin-tin radii are in good agreement with experimental results.

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FILL-IN TECHNOLOGY FOR HIGH DIMENSIONAL PRECONDITIONER LIU Xing-ping, MO Ze-yao, PENG Li-tian 2000, 17(5): 476-482.  Abstract ( )   PDF (153KB) ( )   It presents an effective fill-in technology for the preconditioners of large sparse linear algebraic equations arising from the difference discretizations of high dimensional physical problems, and discusses the relations between fill-in and numerical costs. By using this technology into the practical problems for verification, numerical results obtained are well coincided with the theoretical analyses.

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THE DISCRETE METHOD OF SEPARATION OF VARIABLES FOR COMPUTATION OF STRESS INTENSITY FACTORS HAN Hou-de, HUANG Zhong-yi, BAO Wei-zhu 2000, 17(5): 483-496.  Abstract ( )   PDF (452KB) ( )   A semi-discrete method is proposed for finding the numerical solution of the boundary value problem(BVP) of Navier's equations on the polygon with a single edge-crack. After a suitable transformation of the coordinates, the BVP is reduced to a discontinuous coefficients problem on a semi-infinite strip, and the semi-discrete approximation of the problem is obtained, equivalent to a BVP of a system of O.D.E's with constant coefficients. Furthermore, the semi-discrete approximation of the BVP can be acquired by a direct method. It is worthwhile to note that, the semi-discrete approximation in the form of separable variables naturally possesses the singularity of the given problem. Finally numerical examples show the effectiveness of the method to calculate the approximation of the stress intensity factors.

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TWO DIMENSIONAL UNSTRUCTURED ADAPTIVE MULTIGRID FOR EULER EQUATIONS WANG Ping, ZHU Zi-qiang, LU Xiao-bin 2000, 17(5): 497-503.  Abstract ( )   PDF (193KB) ( )   The AUSM+ scheme which was developed on structured grid has been extended to be used on unstructured grid. The monotone linear reconstruction procedure using Green-Gauss theory is utilized to obtain second order spatial accuracy. Barth's limiter is employed to prevent solution spurious oscillations. An adaptive multigrid strategy is used to accelerate the convergence. Numerical results for several test cases are presented.

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EFFECTS OF NON-MAXWELLIAN ELECTRON VELOCITY DISTRIBUTION ON STIMULATED SCATTERING ZHANG Jia-tai 2000, 17(5): 504-510.  Abstract ( )   PDF (206KB) ( )   According to the linear theory of stimulated scattering instabilities taking into count kinetic effects, the frequencies and the damping rates of an electron plasma wave (PEW) and of an ion-acoustic wave (IAW) are computed in a maxwellian electron velocity distribution function(n=2) to the non-Maxwellian saturated (n=5) limit. Stimulated Raman scattering and stimulated Brillouin scattering are analyzed, the results show that in high-Z plasmas or in laser hot spots with moderate Z, the damping rate of an electron plasma wave is substantially lower and the frequency of an ion-acoustic wave significantly higher than those in a Maxwellian distribution, and its damping rate is also lower.

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PARAMETER IDENTIFICATION PROBLEM FOR PARABOLIC EQUATIONS USING EVOLUTIONARY ALGORITHMS XIONG Sheng-wu, LI Yuan-xiang, KANG Li-shan, CHEN Yu-ping 2000, 17(5): 511-517.  Abstract ( )   PDF (174KB) ( )   A general approach based on evolutionary algorithms to inverse parameter identification problems of PDEs is introduced. The evolutionary algorithms is used for solving the inverse problem as an optimization problem. This approach can evolve the optimal coefficient estimation by genetic algorithms (GA) in the giving function space of unknown parameter from observation data objectively and automatically. The approach has also been applied to parameter identification problem of linear and quasi linear parabolic equations. The numerical results demonstrated the effectiveness of this method.

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VARIABLE DOMAIN VARIATIONAL FINITE ELEMENT APPROACH TO IA INVERSE PROBLEM OF UNSTEADY TRANSONIC FLOW AROUND OSCILLATING AIRFOILS GUO Jia-hong, LIU Gao-lian 2000, 17(5): 518-524.  Abstract ( )   PDF (201KB) ( )   On the basis of the variational principles developed in Ref[1], a finite element method(FEM) is constituted for soluting the inverse problem of 2-D unsteady transonic flow around oscillating airfoils, incorporating the non-reflecting far-field boundary conditions and a new unsteady Kutta condition[7]. All unknown boundary(airfoil contour) and discontinuities(shocks and free trailing vortex sheets) are handled(captured) via the functional variation with variable domain and artificial density concept. For the numerical realization of variable-domain variation, a special finite element with self-adjusting nodes is also suggested herein. The numerical results show that the present method is effective for the design of unsteady airfoil.

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MCMGP3-A 3-D MULTIGROUP P3 MONTE CARLO NEUTRON TRANSPORT CODE AND BENCHMARKS DENG Li, XIE Zhong-sheng, ZHANG Jian-ming, LI Shu 2000, 17(5): 525-531.  Abstract ( )   PDF (185KB) ( )   It outlines MCMGP3-A 3-D multigroup P3 Monte Carlo neutron transport code, which is designed for computation of reactor critical safety. It is developed from the coupled neutron and photon transport Monte Carlo code MCNP with continual point cross sections and the continual point cross section module of MCNP code has been replaced by multigroup cross section module. MCMGP3 code is with the capablilities of MCNP geometry treatment, counting, deviation reducing techniques and plot. Either macroscopic or microscopic cross sections can be used.The neutron scattering angular distribution adopts P3 approximation and generalized Gaussian quadrature scheme. The sample problem results prove the computational correctness of the code. MCMGP3 code can treat steady or unsteady porblems with exterior source and critical problems. It suits various cross section formats and the energy groups can be expanded easily from one group to multigroup. In addition, the MCMGP3 code has successfully realized the coupled with the reactor lattic code WIMS. It can be used to simulate the full reactor problems.

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THE NUMERICAL STUDY OF FLOWFIELDS AROUND A SEPARATING MISSILE ZHOU Wei-jiang, BAI Peng, MA Han-dong 2000, 17(5): 532-536.  Abstract ( )   PDF (140KB) ( )   The flowfields around a separating missile in supersonic free stream are studied numerically. Several typical flowfield structures in various separation distances are obtained. Two typical flow patterns are consistent very well with that observed in experiment. When the separation distance is small, the region between two stages is filled with "dead water" flow, the bottom drag of forebody is negative, the typical "afterbody effect" phenomenon occurs. When the separation distance is large, the complex interactive waves system is observed. After centain separation distance, the normal shock wave is formed in the front of the separated flow region before afterbody, hence the afterbody effect to forebody has been cut off.

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APPLICATION OF GMRES ALGORITHM IN THE PREDICTIONS OF TWO-DIMENSIONAL INVISCOUS STEADY FLOWS NING Fang-fei, XU Li-ping 2000, 17(5): 537-547.  Abstract ( )   PDF (417KB) ( )   Two types of preconditionings coupled with the GMRES algorithm for the two-dimensional Euler equations are presented.An approach is used for reducing the memory requirement of GMRES algorithm and preserving its efficiency.With the calculations of two inviscous flows,the GMRES algorithm and the associated two preconditionings are analyzed,and its comparison with the DDADI method is also presented.The calculation results of the NACA0012 airfoil transonic flow and the supersonic GAMM flow show that the GMRES algorithm coupled with the two preconditionings has superior advantage on convergence rate compared to DDADI method.Furthermore,from the results it can be seen that the LUSGS preconditioning is slightly better than the ILU preconditioning.

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SOFTWARE DEVELOPMENT AND APPLICATION OF COMPOSITIONAL MODEL WITH THREE PHASE AND 3D FOR OIL/GAS RESERVOIR YE Ji-gen, WU Xiang-hong 2000, 17(5): 548-552.  Abstract ( )   PDF (138KB) ( )   A new solution method to compositional model is investigated,which is implicit to pressure and saturation of oil and gas,and explicit to mole fractions of components.The number of equations to be solved simultaneously is much less than that of the fully implicit method,but the stability is as good as such one.It is also shown that the present compositional software have good accuracy and exciting computation speed.

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A METHOD OF DISCRETE ADJOINT OPERATOR IN DATA ASSIMILATION FOR THE PREDICTION OF THE VERTICAL DISTRIBUTION OF SEA TEMPERATURE HE Bai-rong, MA Ji-rui, HAN Gui-jun, LI Dong 2000, 17(5): 553-559.  Abstract ( )   PDF (182KB) ( )   To carry out the data assimilation of sea temperature observations the adjoint method is applied, which can provide an accurate initial temperature field for numerical prediction. For simplicity we consider only a one-dimensional sea temperature model, what are discussed in this paper involve, the idea of the adjoint method, the optimal procedure and the finite difference schemes of sea temperature control equation and adjoint equation. Numerical results are also presented for describing the varying sea temperature field.

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THE INFLUENCE OF ABSORPTION SPECTRUM OF α-Al2O3 BY NEUTRON RADIATION-INDUCED F3 CENTER CHEN Jun, LIN Li-bin 2000, 17(5): 560-564.  Abstract ( )   PDF (141KB) ( )   The energy band structure,density of state and Mulliken charge density of the F3-center in α-Al2O3 are studied by an embedded-cluster model,when H-like wave function is used for F-center.The optical transition model of the color center is also discussed.It found one single energy level and one doubly-degenerate energy level in the fundamental gap of the crystal with F3-center.There is a new transition from defect energy level to conduction band and the transition energy is 3.54 eV.Comparing with the absorption spectrum of α-Al2O3 by high-energy and great flux neutron radiation,shows that 0.356 μm(3.483 eV) experimental absorption peak should be due to the F3-center.Also,it found the charge density is less in the site of F3-center than that of Fcenter in α-Al2O3 crystal.

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LOCAL EXACT NUMERICAL METHODS FOR BOUNDARY VALUE PROBLEMS OF ODEs MOU Zong-ze, LONG Yong-xing, PENG Dian-yun, MIAO Jing, HUANG Lin 2000, 17(5): 565-572.  Abstract ( )   PDF (216KB) ( )   It proposes three kinds of new difference schemes(exponential type,oscillatory type and exponential-oscillatory type) based on the coefficient structural characteristic and the behaviour of solution in the ODEs.The schemes can describe excellently dependent variables with steep gradient,shear layer and/orhighly oscillations.

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AERODYNAMIC OPTIMIZATION DESIGN THROUGH SELF-ADAPTIVE GENETIC ALGORITHM WANG Xiao-peng, GAO Zheng-hong 2000, 17(5): 573-578.  Abstract ( )   PDF (163KB) ( )   A simple genetic algorithm(SGA) is modified to form self-adaptive genetic algorithm(SAGA) in aerodynamic optimization design. Real number coding skill is used in the algorithm to represent individuals of population, while binary coding and encoding are not required. In order to improve the quality and efficiency of optimization design, crossover and mutation operators are designed with respect to specified problem. Then self-adaptive genetic algorithm is adopted to maximize lift-to-drag ratio of transonic airfoil and wing as examples. Analysis approves the designed results reasonable.

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THE BOUNDARY ELEMENT METHOD OF PRESSURE BEHAVIOR MODEL OF LATERAL DRILLING AND FORMATION DAMAGE EVALUATION XIANG Kai-li, GUO Jian-chun, LI Yun 2000, 17(5): 579-587.  Abstract ( )   PDF (241KB) ( )   Lateral wells increasing, it becomes more and more important to evaluate the pressure performance and formation damage in the heterogeneous reservoirs with lateral drilling. Considering the properties of lateral drilling in the heterogeneous reservoirs, the paper has presented a mathematical model of 3D unsteady flow. Since it is intricate to solve the model by analytical method, the model is solved by boundary element method and regional division technique for the pressure performance of lateral drilling well produced at constant rate or bottom well pressure. By reasonable incorporation of pseudo skin factor, dimensionless damaged radius, dimensionless well storage coefficient, and permeability of damaged region; we can get type curves, which can be used for evaluation of formation damage caused by lateral drilling. The application to well test data of a lateral-drilling well of Liaohe oil field in the East China shows that the model and method are all valid.

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ENGINERRING CALCULATION FOR FIXING SEAT OF DAPER ON AERIAL CONDUCTOR HE Xiao-xiong, LI He-qin 2000, 17(5): 588-592.  Abstract ( )   PDF (121KB) ( )   Dampers are widely used in aerial conductors to reduce the severity of aeolian vibration and the accompanying fatigue damage to conductor strands and fittings. It describes a physics model and deduces a numerical calculation method about fixing seats of dampers on aerial conductors by calculating the amplitude ratio, so a new design method is given in the preventing conductors from aeloian vibration and construction of transmission line.