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25 May 2001, Volume 18 Issue 3 Previous Issue    Next Issue

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NUMERICAL SIMULATION OF THE SOUND FIELD GENERATED BY AXISYMMETRIC JET HU Guo-qing, LIU Ming-yu, FU De-xun, MA Yan-wen 2001, 18(3): 193-198.  Abstract ( )   PDF (260KB) ( )   An algorithm is proposed to combine Kirchhoff integral and an unsteady flow computation. Axisymmetric jet flows are given by DNS using 5-order accurate upwind compact scheme and 3-order accurate Runge-Kutta scheme. Kirchhoff integral is used to predict the far-field sound. Numerical results show that far-field sound pressure has the directivity and reaches maximal value at 20° diverged from the flow direction. The directivity is attenuating while the propagation distance is increasing.

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GRID OVERLAPPING FOR IMPLICIT PARALLEL COMPUTATION OF N-S EQUATIONS ZOU Hui, LI Jin-jing, WU Zi-niu 2001, 18(3): 199-205.  Abstract ( )   PDF (279KB) ( )   Recently Wu Z N and Zou H proposed an overlapping grid method.The suitability of applying the method to parallel computation of steady and unsteady compressible inviscid flows with three-point block-tridiagonal implicit schemes was addressed in the paper [1],and an easily usable interface treatment was constructed and analyzed for both steady and unsteady problems.This method is here applied to the computation of N-S equations.In both steady and unsteady cases a good absolute parallel efficiency has been still demonstrated for bidimensional subsonic and transonic flow computations.

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A COMPARISON BETWEEN TWO AVERAGING METHODS OF MULTI-GROUP PARAMETERS IN ICF RADIATION TRANSFER CALCULATION FENG Ting-gui, LAN Ke, LAI Dong-xian 2001, 18(3): 206-210.  Abstract ( )   PDF (196KB) ( )   Comparing two multigroup methods that the means of Rosseland mean at local material temperature (method 1) and the means based on the local effective radiation temperature (method 2),a conclusion that method 1 is superior to the method 2 in ICF radiation transfer calculation is drawn. Some numerical results are presented.

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HOMOGENEOUS WAVES AND EVANESCENT WAVES IN NEAR-FIELD DIFFRACTION OF A SMALL APERTURE DENG Xiao-jiu, WU Ben-ke 2001, 18(3): 211-214.  Abstract ( )   PDF (144KB) ( )   Using the angular spectrum representation,the homogeneous and evanescent waves in near-field diffraction of a small aperture are examined.As an example,the diffraction of a plane wave by a circular aperture is considered in detail,and some new results have been obtained.

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A RAY SPLIT-OFF AND TRACING APPROACH FOR ANALYZING THE SPECTRAL REFLECTING PERFORMANCE OF A SEMITRANSPARENT FLUID LAYER WITH UNDULANT SURFACE XIA Xin-lin, HUANG Yong, TAN He-ping 2001, 18(3): 215-218.  Abstract ( )   PDF (203KB) ( )   A ray split-off and tracing approach is presented to analyze the apparent spectral reflecting performance of a semitransparent fluid layer with undulant surface.For parallel incidence and diffuse incidence of the spectral radiation,the regular ray tracing and the inverse ray tracing are separately employed to realize tracing the ray split-off process.With a clear and simple solving idea, the approach possesses a high calculating rate and small demands for the EMS memory,and is flexible for this kind of problems.The results of the calculating example show the following facts.For diffuse incidence of the spectral radiation,the undulant curve of the surface lowers the reflecting ability of the fluid layer.While for parallel incidence of the spectral radiation,two kinds of different influences on the reflecting ability may be caused by the undulant curve.

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THE THEORETICAL SIMULATION AND COMPUTER SOFTWARE OF INFRARED RADIATION FIELDS OF TARGETS ON THE SEA YANG Bao-cheng, SHEN Guo-tu, MAO Hong-xia, GAO Lan-xiang, HONG Zhen-qing, ZHU Wen-yong, GAO Jing 2001, 18(3): 219-224.  Abstract ( )   PDF (234KB) ( )   A theoretical model of the temperature field and infrared radiation field is presented,the physical characteristic of which is the separate treatment of the three wavelength regions of the radiation of the sun,the sea and atmosphere background,and the target,and based on the model the complete set of equations of the temperature field and radiation field for the ship in question are obtained that are then used to developed a computer software to obtain the field distribution and to simulate the thermal images of the target.The flow chart of the software is presented and key points concerning the programming are discussed.The numerical results and the simulated graphs for the infrared images of a ship are calculated using the software.The results are compared with the real infrared images of the ship and the main features of the two results are in good agreement.

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NUMERICAL STUDY ON THE LAMINAR FLUID FLOW AND HEAT TRANSFER CHARACTERISTICS IN PERIODIC DIVERGENT-CONVERGENT CHANNELS XU Jia-ying, WANG Qiu-wang, YANG Xiao-yu, WANG Liang, TAO Wen-quan 2001, 18(3): 225-229.  Abstract ( )   PDF (210KB) ( )   The laminar flow and heat transfer of water in periodic fully-developed divergent-convergent channels has been investigated numerically.The SIMPLE algorithm and body-fitted coordinates (BFC) are used.The periodic boundary condition is treated using the method proposed by Amano.It is found that under the range of Re=100~1 000,the friction factor is about 10%~200% more than that of parallel plate channel,while the average Nusselt number is about 40%~320% more than that of parallel plate channel.

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PARALLEL COMPUTATION FOR THE THIN FILM DEPOSITION ON THE NOW SHU Ji-wu, ZHENG Wei-min, SHEN Mei-ming, HUANG Han-chen 2001, 18(3): 230-234.  Abstract ( )   PDF (247KB) ( )   An approach to the parallelization is proposed on the network of workstation,that simulates the produce of the thin film deposition with a scale of 100×100×100 atomic sites in three-dimension by Monte Carlo method.It uses a efficient parallel algorithm for the thin film deposition simulation using domain decomposition and asynchronous parallel communication,and adopts the reasonable division of domain with the topology geometric of space filling in the film deposition process.The results show that parallel processing generated by these methods can make communication overhead fallen off considerably,and the parallel performance of algorithm improved and computation time for the thin film deposition decreased largely.

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THE METHOD OF ORTHOGONAL COLLOCATION USED IN CHEMICAL ENGINEERING WITH FRACTAL STRUCTURE LIU Fu-sheng, MA Zheng-fei, WANG Sheng 2001, 18(3): 235-240.  Abstract ( )   PDF (245KB) ( )   The method of orthogonal collocation in Euclid's space has been extended to fractal space,with which the numerical computation of reaction-diffusion problem in chemical engineering has been also performed.The comparisons between calculated results and related analytical solutions show that this extended method gives the same results as theoretical ones,and permits to be used as a powerful numerical tool for the detailed analysis of chemical processes with fractal structure.

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A CLASS OF GAUSS SCHEMES WITH STAGGERED GRIDS IN TWO DIMENSIONS QIU Jian-xian, DAI Jia-zun 2001, 18(3): 241-246.  Abstract ( )   PDF (199KB) ( )   It presents a class of the second order accurate explicit Gauss schemes with staggered grids for the computation of solutions of single hyperbolic conservation laws in two dimernsions, these schemes are Riemann solver-free and Maximum and Minimum Bounds under the restriction of CFL,and have been extended to system of hyperbolic conservation laws. Because these schemes are constructed under staggered grids and Riemann solver-free,the advantages of these schemes compared to other TVD schemes such as Harten's are:no complete set of eigenvectors is needed and hence weakly hyperbolic system can be solved,faster and programming is much simpler.The numerical solutions obtained in computation Riemann problem are satisfactory.

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MULTIFRACTAL CALCULATION OF THIN FILM GROWTH SUN Xia, FU Zhu-xi, WU Zi-qin 2001, 18(3): 247-252.  Abstract ( )   PDF (264KB) ( )   Regular fractal has ideal scale-invariance.But the probability distribution curve and the range of scale-invariance of random fractal (for example thin film growth) are related to the calculation method.The scale-invariance is not good and the multifractal spectrum is not smooth when the probability is calculated by variance from average height.The range of scale-invariance can be extend to 3 orders of magnitude and the multifractal spectrum is smooth when the probability is calculated by height based on the bottom of the film.An extending method is here used to correct the deviation of gray level setting-up so as to improve the multifractal spectrum.The effect of the range of the moment order q is discussed as well.

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EMISSION AND SPATIAL DISTRIBUTIONS OF BSEs IN SOLIDS UNDER THE ACTION OF LOW ENERGY ELECTRON BY MONTE CARLO SIMULATION TAN Zhen-yu, HE Yan-cai 2001, 18(3): 253-258.  Abstract ( )   PDF (263KB) ( )   Using Monte Carlo method, both emission and spatial distributions of the backscattered electrons (BSEs) of the solids Al,Cu,Ag,Au under the action of low energy electrons with energy E0 ≤ 5keV keV have been simulated and calculated. Mott cross section and the modified Bethe equation are used to describe the elastic and inelastic scattering of electrons in solids, respectively. The energy distribution, surface spatial distribution, depth distributioin in solids and angle distribution of BSEs have been obtained. The dependence of angle distribution of BSEs on the energy distribution, surface spatial distribution and depth distribution of BSEs are also calculated, describing the distribution regularity and emission of BSEs systematically.

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CALCULATION OF THE ENERGY LEVELS FOR MULTI-WELL POTENTIAL BY MEANS OF B-SPLINE TECHNIQUE HUI Ping, TAN Zhong-ming, SHI Ting-yun 2001, 18(3): 259-262.  Abstract ( )   PDF (183KB) ( )   The B splines method is used to calculate eigenvalues for one and two dimensional multi-well potential.Comparisons are made with calculations using Gaussian bases for one dimensional potential.The B splines bases is shown to be accurate,flexible,and efficient.

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GRIDLESS PARTICLE SIMULATION OF ELECTROSTATIC PLASMAS YIN Yan, CHANG Wen-wei, MA Yan-yun, YUE Zong-wu, CAO Li-hua, XU Han 2001, 18(3): 263-270.  Abstract ( )   PDF (324KB) ( )   The 3-D Fast Multipole Method, a kind of gridless particle simulation method, is described and improved to obtain higher accuracy. A spherical particle with reduced dimensional motion model is presented. As examples, the spatial distribution of the potential in dust plasma and the instability produced by electrons streaming through ions are simulated. The results of simulations are in agreement with the theory.

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NON-OSCILLATORY SELECTION (NOS) SCHEME FOR HYPERBOLIC EQUATIONS YU Heng, SHUI Hong-shou, ZHANG Hui-sheng 2001, 18(3): 271-275.  Abstract ( )   PDF (219KB) ( )   The TVD conditions of finite difference schemes are interpreted on geometrical views for hyperbolic equations,and from it the non-oscillatory conditions are derived for conventional second-order schemes.A mainly third-order non-oscillatory scheme (NOS) is developed.Numerical experiments show high order,non-oscillation,simplicity and symmetric diffusion of the scheme.

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A NEW METHOD UNFOLDING SPECTRA FOR THE SOFT X-RAY SPECTROMETER JIANG Shao-en, ZHENG Zhi-jian, SUN Ke-xun 2001, 18(3): 276-280.  Abstract ( )   PDF (227KB) ( )   A new method unfolding soft X-ray spectra for a soft X-ray spectrometer (SXS),which is based on maximum entropy principle (ME),is put forward.The spline fit method is used to smooth the discontinuities between the channels at the filters edge responses.The convergent speed of ME is rapid,the stability and the deconvolution accuracy appear to be good.ME's unfolding error can achieve 5%.The method is capable of unfolding the soft X-ray spetra for the soft X-ray spectrometer.

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NUMERICAL METHOD OF DIFFERENTIAL EQUATION WITH NEURAL NETWORKS SHANG Zhi, LIU Rui-lan, SU Guang-hui, JIA Dou-nan 2001, 18(3): 281-284.  Abstract ( )   PDF (161KB) ( )   Neural networks has excellent self-learning and self-adaptive characteristics, with which a new calculation form is developed. In this form Cardinal B-spline wavelet analysis is also applied. A numerical example is given through calculating one-dimension boundary layer equation.

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MONTE CARLO METHOD FOR REACTOR DUCT SHIELDING CALCULATION JIANG Xin-biao, CHEN Da, XIE Zhong-sheng, ZHANG Ying 2001, 18(3): 285-288.  Abstract ( )   PDF (152KB) ( )   The sampling method by coupling criticality source direction biasing and the exponential transform is established for duct shielding calculation.In sample problem studying,the optimal source direction biasing parameter p1、exponential transform parameter p2 are supposed and the variance of duct calculating results by using this method is shown to reduce efficiently.Correction calculation for the duct of Nuclear Power Institute of China (NPIC) pulsed reactor shows the results are more close to the measured ones.