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25 December 1991, Volume 8 Issue 4 Previous Issue    Next Issue

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NUMERICAL METHOD FOR THE VISCOUS FLOW AROUND A CIRCULAR CYLINDER WITH PERIODIC ONCOMING FLOW FROM INFINITY Hu Yang, Shi Changchun, Chen Yaosong 1991, 8(4): 337-346.  Abstract ( )   PDF (478KB) ( )   Two-dimensional imcompressible viscous flows around a circular cylinder with periodic oncoming flow from infinity are investegated. By means of spectrum method, the stream functions are developed into Fourier series, so the stream functions depend on angle 0 continuousely. Numerical calculations are implemented for stream functions as well as vortices for the case Kc=4 and Re=200. The results manifeste that the method used here has the advantage of simplicity and saving computer time comparing with the method of fully discretiged N-S egs. and discretiged vortices method.

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THEORETICAL CALCULATION OF THE QUANTITY OF CORNEA ABLATION IN LASER MYOPIA THERAPY Yang Yuanlong, Chen Zhong 1991, 8(4): 347-358.  Abstract ( )   PDF (703KB) ( )   Basing on the statistical model of eyes, using self-consistency single lens approximation and matrix optical theorem, we have calculated the backward shift of focus under the condition of different myopia degrees, and the quantity of corneal ablation for three different causes of myopia. The calculation shows that the maximum ablation is only 50um less than one tenth of the total corneal thickness although the myopia is 1000 degrees.We also consider using optical system to alternate illuminative distribution to achieve adjusting myopia, based on the gaussian distribution of laser beam.

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h4 EXPONENTIAL FINITE DIFFERENCE SCHEME FOR CONVECTIVE DIFFUSION EQUATION Chen Guoqian, Yang Zhifeng, Gao Zhi 1991, 8(4): 359-372.  Abstract ( )   PDF (705KB) ( )   A kind of exponential finite difference schemes with h4 consistency are developed in this study. The h4 scheme is obtained from a second-order modification of the convective coefficients and the source term in an h2 scheme, and the modification could be determined once and for all from computational information of the h2 scheme, which bring great convenience to the h4 scheme. The proposed exponential scheme are unconditionally stable, and show a excellent accuracy and adaptability to great gradient variation when applicated in illustrative computations of 1D to 3D fluid flow model problems.

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ANALYSIS AND COMPUTATION OF DEGENERATE FOUR-WAVE MIXING IN PHOTOREFRACTIVE CRYSTALS Fu Changhai, Li Qingxing, Yu Zhenxin 1991, 8(4): 373-376.  Abstract ( )   PDF (282KB) ( )   A boundary correction method is proposed for the numerical solution of the degenerate four-wave mixing in photorefractive crystals. The present method can easily deal with the problem of split boundary conditions. Results from the present method shows that the incidence angles of and ratio of pump beam intensity in the PCR lead to a significant improvement; The line absorption of the interacting beams by the crystals is nonlinear in the PCR.

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THE DOMAIN DECOMPOSITION METHOD WITH OVERLAPPING FOR GENERAL ELLIPTIC PARTIAL DIFFERENTIAL EQUATIONS Chu delin 1991, 8(4): 377-386.  Abstract ( )   PDF (501KB) ( )   In this paper, the domain decompositions method with overlapping for general elliptic partial differential equation is studied, its convergence is proven based on maximum principle.

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APPLICATION ANALYSIS OF MULTI-GRID METHOD FOR SOLVING THE NUCLEAR REACTOR DIFFUSION EQUATIONS Qiu Xichun, Xue Youyi 1991, 8(4): 387-394.  Abstract ( )   PDF (488KB) ( )   per presents some preliminary work on the applications of multi-grid method for solving the 2D reactor diffusion Equations. We used the multi-grid method with V-cycle and W-cycle for solving a model problem and comparied the results by SOR. Numerical results showed that the multi-grid method with W-cycle is the best. It is faster four time than the SOR.

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MONTE-CARLO STUDIES OF RADIATION DAMAGE IN THE FIRST WALL CAUSED BY FUSION NEUTRON Gao Xinghua, Huo Yukun, Pan Zhengying, Shao Qiyun, Chen Janxin, Wu Sheming 1991, 8(4): 395-406.  Abstract ( )   PDF (681KB) ( )   A Monte-Carlo Neutron Transport Program and Neutron Radiation Damage Program are presented for studying radiation damage in the First Wall. The programs are used to static multi-component amorphous target. With the average wall load 1MW/m2, the following calculating results for EHR first wall (type 316 stainlees steel)have been performed using designed neutron spectrums at EHR first wall: the PKA energy spectrums (30eV to 1MeV), average displacement per atom rate (20.6dpa/a), average helium and hydrogen production rates (247.18appm/a and 721.15appm/a). It is shows that Hybrid Reactor's radiation damage more serious than pure Fusion Reactor's by comparison of above results and EHP's calculated results in the same wall load. The cross-section data from MC (87) n library is used in this calculation.

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NUMERICAL SIMULATION OF EXPLOSIONS OF FUEL VAPOUR CLOUD USING TVD SCHEME Peng Jinhua, Tang Mingjun 1991, 8(4): 407-412.  Abstract ( )   PDF (363KB) ( )   In this paper, Total Variation Diminishing (TVD) scheme was used to simulate the two-dimensional axisymmetric blast fields from explosions of fuel vapour cloud. Numerical solution fo overpressures and trajectories of blast waves are agreement with the experimental results.

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THE MUSCL SCHEME OF FLOW VARIABLES WITH LINEAR PROFILES Ma Dawei, Zang Guocai 1991, 8(4): 413-418.  Abstract ( )   PDF (351KB) ( )   In this article, we suggest a new linear function and prove that the MUSCL scheme would have second-order accuracy, if the function was used to approximate the initial-value distribution of flow variables in every mesh. The scheme is suitable for the Enlerian calculation when monotonicity condition and some dissipative mechanisms are introduced. We approximate the characteristic equations with shock jump relations near discontinuities and resolve the problem of using characteristic method in whole flowfield calculation. Finally, we present the numerical examples of Emery problem and a rocket jet problem.

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THE SCALE FACTOR AND UNIVERSAL CONSTANT FOR ASYMMETRIC UNIMODAL MAPPING Liu Ruilin, Peng Shouli 1991, 8(4): 419-427.  Abstract ( )   PDF (521KB) ( )   In this paper, the scale factor and universal constant are discussed for asymmetric unimodal mapping. The convergence are obtained by redefining the scale factor and the universal constant. We have given a algorithm.

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THE BOUNDARY ELEMENT ANALYSIS OF AXISYMMETRIC TRANSIENT HEAT CONDUCTION PROBLEM Yao Shuoguang, Zhu Deshu 1991, 8(4): 428-436.  Abstract ( )   PDF (489KB) ( )   In this paper, the boundary integral equation and the fundamental solution of axisymmetric transient heat conducation problem are derived from the boundary integral equation and fundamental solution of three dimension transient potential problem, and given in discretization form of the boundary element equation. On this basis, several axisymmetric thermal problems with different boundary conditions are calculated. Obtained results show that the method formed in this pape is reliable, and have good accuracy and good stability. It can be used to analyze the temperature field of axisymmetric body in engineering.

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A NEW HIGHER ORDER ACCURACY NUMERICAL FORMULA FOR DOUBLE INTEGRAL Wu xinyuan, Wu Hongwei 1991, 8(4): 437-441.  Abstract ( )   PDF (273KB) ( )   An extension of result in [1] to two dimension is derived in this paper. The new numerical formula for double integral possesses the all advantage of Simpson's formula but the degree of accuracy is increased by two order than that of Simpson's formula.The numerical tests show that the new numerical formula of this paper is more efficient.